Earth and Planetary Sciences › Atmospheric Science

Geology and Paleoclimatology Research

Works Count: 280588

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Description

This cluster of papers encompasses research on climate change and paleoclimatology, including topics such as glacial cycles, Holocene climate variability, sea level fluctuations, monsoon dynamics, greenhouse warming, ice core records, solar influence on climate, and atmospheric CO2 concentrations over various timescales.

Keywords

Climate Change; Paleoclimatology; Glacial Cycles; Holocene; Sea Level; Monsoon Dynamics; Greenhouse Warming; Ice Core Records; Solar Influence; Atmospheric CO2

A Geologic Time Scale 2004

2005-03-17

Felix M. Gradstein , Linda A. Hinnov , James G. Ogg +7 more

An international team of over forty stratigraphic experts have helped to build the most up-to-date international stratigraphic framework for the Precambrian and Phanerozoic. This successor to A Geologic Time Scale … An international team of over forty stratigraphic experts have helped to build the most up-to-date international stratigraphic framework for the Precambrian and Phanerozoic. This successor to A Geologic Time Scale 1989 by W. Brian Harland et al. (CUP 0521 387655) begins with an introduction to the theory and methodology behind the construction of the new time scale. The main part of the book is devoted to the scale itself, systematically presenting the standard subdivisions at all levels using a variety of correlation markers. Extensive use is made of isotope geochronology, geomathematics and orbital tuning to produce a standard geologic scale of unprecedented detail and accuracy with a full error analysis. A wallchart summarising the whole time scale, with paleogeographic reconstructions throughout the Phanerozoic, is included in the back of the book. The time scale will be an invaluable reference source for academic and professional researchers and students.

A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records

2005-01-17

L. E. Lisiecki , Maureen E. Raymo

We present a 5.3‐Myr stack (the “LR04” stack) of benthic δ 18 O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first … We present a 5.3‐Myr stack (the “LR04” stack) of benthic δ 18 O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first benthic δ 18 O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene‐Pleistocene derived from tuning the δ 18 O stack to a simple ice model based on 21 June insolation at 65°N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly more variance in benthic δ 18 O than previously published stacks of the late Pleistocene as the result of higher‐resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally, the relative phases of the stack's 41‐ and 23‐kyr components suggest that the precession component of δ 18 O from 2.7–1.6 Ma is primarily a deep‐water temperature signal and that the phase of δ 18 O precession response changed suddenly at 1.6 Ma.

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Evolution of Asian monsoons and phased uplift of the Himalaya–Tibetan plateau since Late Miocene times

2001-05-01

Zhisheng An , John E. Kutzbach , Warren L Prell +1 more

INTCAL98 Radiocarbon Age Calibration, 24,000–0 cal BP

1998-01-01

Minze Stuiver , Paula Reimer , Édouard Bard +7 more

The focus of this paper is the conversion of radiocarbon ages to calibrated (cal) ages for the interval 24,000–0 cal BP (Before Present, 0 cal BP = AD 1950), based … The focus of this paper is the conversion of radiocarbon ages to calibrated (cal) ages for the interval 24,000–0 cal BP (Before Present, 0 cal BP = AD 1950), based upon a sample set of dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediment. The 14 C age–cal age information, produced by many laboratories, is converted to Δ 14 C profiles and calibration curves, for the atmosphere as well as the oceans. We discuss offsets in measured l4 C ages and the errors therein, regional 14 C age differences, tree–coral 14 C age comparisons and the time dependence of marine reservoir ages, and evaluate decadal vs . single-year 14 C results. Changes in oceanic deepwater circulation, especially for the 16,000–11,000 cal BP interval, are reflected in the Δ 14 C values of INTCAL98.

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Oxygen Isotope and Palaeomagnetic Stratigraphy of Equatorial Pacific Core V28-238: Oxygen Isotope Temperatures and Ice Volumes on a 105 Year and 106 Year Scale

1973-06-01

Nicholas J Shackleton , Neil D. Opdyke

Abstract Core Vema 28-238 preserves an excellent oxygen isotope and magnetic stratigraphy and is shown to contain undisturbed sediments deposited continuously through the past 870,000 yr. Detailed correlation with sequences … Abstract Core Vema 28-238 preserves an excellent oxygen isotope and magnetic stratigraphy and is shown to contain undisturbed sediments deposited continuously through the past 870,000 yr. Detailed correlation with sequences described by Emiliani in the Caribbean and Atlantic Ocean is demonstrated. The boundaries of 22 stages representing alternating times of high and low Northern Hemisphere ice volume are recognized and dated. The record is interpreted in terms of Northern Hemisphere ice accumulation, and is used to estimate the range of temperature variation in the Caribbean.

High-resolution record of Northern Hemisphere climate extending into the last interglacial period

2004-09-01

K. K. Andersen , Nobuhiko Azuma , Jean-Marc Barnola +7 more

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Origin and Consequences of Cyclic Ice Rafting in the Northeast Atlantic Ocean During the Past 130,000 Years

1988-03-01

Hartmut Heinrich

Deep-sea sediment cores recovered from the Northeast Atlantic Ocean were examined in order to elucidate the influence of the Earth's orbital parameters on major ice rafting. Analyses of coarse-grained ice-rafted … Deep-sea sediment cores recovered from the Northeast Atlantic Ocean were examined in order to elucidate the influence of the Earth's orbital parameters on major ice rafting. Analyses of coarse-grained ice-rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal. Since 130,000 yr B.P., dropstone layers have been deposited each half period of a precessional cycle (11,000 ± 1000 yr). Ice rafting occurs during times of winter minimum/summer maximum insolation and summer minimum/winter maximum insolation. In the first case, high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter. In the second case, growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater. Both situations result in a southward penetration of polar water. Thus, the marine record of dropstones documents ice rafting not only during Weichselian stades but also during cold events within interstades. The regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes, not only in the region of the North Atlantic Ocean but also in remote areas such as the Pacific Ocean and the Antarctic.

Persistent Solar Influence on North Atlantic Climate During the Holocene

2001-12-07

Gérard C. Bond , Bernd Kromer , J. Beer +7 more

Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a … Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic's "1500-year" cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.

The Holocene Asian Monsoon: Links to Solar Changes and North Atlantic Climate

2005-05-05

Yongjin Wang , Hai Cheng , R. Lawrence Edwards +7 more

A 5-year-resolution absolute-dated oxygen isotope record from Dongge Cave, southern China, provides a continuous history of the Asian monsoon over the past 9000 years. Although the record broadly follows summer … A 5-year-resolution absolute-dated oxygen isotope record from Dongge Cave, southern China, provides a continuous history of the Asian monsoon over the past 9000 years. Although the record broadly follows summer insolation, it is punctuated by eight weak monsoon events lasting approximately 1 to 5 centuries. One correlates with the "8200-year" event, another with the collapse of the Chinese Neolithic culture, and most with North Atlantic ice-rafting events. Cross-correlation of the decadal- to centennial-scale monsoon record with the atmospheric carbon-14 record shows that some, but not all, of the monsoon variability at these frequencies results from changes in solar output.

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The Last Glacial Maximum

2009-08-07

Peter U. Clark , Arthur S. Dyke , Jeremy D. Shakun +6 more

The Melting Is in the Details Global sea level rises and falls as ice sheets and glaciers melt and grow, providing an integrated picture of the changes in ice volume … The Melting Is in the Details Global sea level rises and falls as ice sheets and glaciers melt and grow, providing an integrated picture of the changes in ice volume but little information about how much individual ice fields are contributing to those variations. Knowing the regional structure of ice variability during glaciations and deglaciations will clarify the mechanisms of the glacial cycle. Clark et al. (p. 710 ) compiled and analyzed more than 5000 radiocarbon and cosmogenic surface exposure ages in order to develop a record of maximum regional ice extent around the time of the Last Glacial Maximum. The responses of the Northern and Southern Hemispheres differed significantly, which reveals how the evolution of specific ice sheets affected sea level and provides insight into how insolation controlled the deglaciation.

Post-glacial re-colonization of European biota

1999-09-01

Godfrey M. Hewitt

Population structure is the result of both present processes and past history. Molecular markers are proving of great value in describing the former, and it is important to similarly determine … Population structure is the result of both present processes and past history. Molecular markers are proving of great value in describing the former, and it is important to similarly determine the latter in order to understand their respective contributions. The study of palaeo-climates has also advanced significantly, and in particular that of the Pleistocene ice ages, which modified species ranges considerably. The last ice age and rapid post-glacial colonization of Europe is summarized. Possible population genetic consequences of expansion northward from southern refugia, and those of remaining in these mountainous regions are discussed. A series of recent case studies are detailed where DNA sequence information has been used to describe species genetic variation and subdivision across Europe. These include a grasshopper, the hedgehog, oak trees, the common beech, the black alder, the brown bear, newts, shrews, water vole, silver fir and house mice. These molecular data confirm southern peninsulas of Europe as major ice age refugia, and in most cases demonstrate that genetically distinct taxa emerged from them. They can thus define genomic differences and so gready augment previous fossil data. The refugial genomes contributed differently in various species to die re-colonization of Europe, with three broad patterns described as paradigms–'grasshopper', 'hedgehog' and 'bear'. These different expansion patterns produced clusters of hybrid zones where they made contact, and it is argued that many species genomes may be further cryptically subdivided. A reduction in diversity from southern to northern Europe in the extent of allelic variation and species subdivision is seen; this is attributed to rapid expansion northward and the varied topography of southern refugia allowing populations to diverge through several ice ages. The differences in DNA sequence indicate that some species have been diverging in refugial regions for a few ice ages at most, whilst distinct lineages in other species suggest much more ancient separation.

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A Scale of Grade and Class Terms for Clastic Sediments

1922-07-01

Chester K. Wentworth

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Geology of mankind

2002-01-01

Paul J. Crutzen

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Correlations between climate records from North Atlantic sediments and Greenland ice

1993-09-01

Gérard C. Bond , Wallace S. Broecker , S. J. Johnsen +4 more

Global silicate weathering and CO2 consumption rates deduced from the chemistry of large rivers

1999-07-01

Jérôme Gaillardet , Bernard Dupré , Pascale Louvat +1 more

Evidence for general instability of past climate from a 250-kyr ice-core record

1993-07-01

W. Dansgaard , S. J. Johnsen , Henrik Clausen +7 more

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Air pressure and cosmogenic isotope production

2000-10-10

John O. Stone

The cosmic ray flux increases at higher altitude as air pressure and the shielding effect of the atmosphere decrease. Altitude‐dependent scaling factors are required to compensate for this effect in … The cosmic ray flux increases at higher altitude as air pressure and the shielding effect of the atmosphere decrease. Altitude‐dependent scaling factors are required to compensate for this effect in calculating cosmic ray exposure ages. Scaling factors in current use assume a uniform relationship between altitude and atmospheric pressure over the Earth's surface. This masks regional differences in mean annual pressure and spatial variation in cosmogenic isotope production rates. Outside Antarctica, air pressures over land depart from the standard atmosphere by ±4.4 hPa (1σ) near sea level, corresponding to offsets of ±3–4% in isotope production rates. Greater offsets occur in regions of persistent high and low pressure such as Siberia and Iceland, where conventional scaling factors predict production rates in error by ±10%. The largest deviations occur over Antarctica where ground level pressures are 20–40 hPa lower than the standard atmosphere at all altitudes. Isotope production rates in Antarctica are therefore 25–30% higher than values calculated by scaling Northern Hemisphere production rates with conventional scaling factors. Exposure ages of old Antarctic surfaces, especially those based on cosmogenic radionuclides at levels close to saturation, may be millions of years younger than published estimates.

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Insolation values for the climate of the last 10 million years

1991-01-01

A. Berger , Marie‐France Loutre

Variations in the Earth's Orbit: Pacemaker of the Ice Ages

1976-12-10

James D Hays , John Imbrie , N. J. Shackleton

1) Three indices of global climate have been monitored in the record of the past 450,000 years in Southern Hemisphere ocean-floor sediments. 2) Over the frequency range 10 –4 to … 1) Three indices of global climate have been monitored in the record of the past 450,000 years in Southern Hemisphere ocean-floor sediments. 2) Over the frequency range 10 –4 to 10 –5 cycle per year, climatic variance of these records is concentrated in three discrete spectral peaks at periods of 23,000, 42,000, and approximately 100,000 years. These peaks correspond to the dominant periods of the earth's solar orbit, and contain respectively about 10, 25, and 50 percent of the climatic variance. 3) The 42,000-year climatic component has the same period as variations in the obliquity of the earth's axis and retains a constant phase relationship with it. 4) The 23,000-year portion of the variance displays the same periods (about 23,000 and 19,000 years) as the quasi-periodic precession index. 5) The dominant, 100,000-year climatic component has an average period close to, and is in phase with, orbital eccentricity. Unlike the correlations between climate and the higher-frequency orbital variations (which can be explained on the assumption that the climate system responds linearly to orbital forcing), an explanation of the correlation between climate and eccentricity probably requires an assumption of nonlinearity. 6) It is concluded that changes in the earth's orbital geometry are the fundamental cause of the succession of Quaternary ice ages. 7) A model of future climate based on the observed orbital-climate relationships, but ignoring anthropogenic effects, predicts that the long-term trend over the next several thousand years is toward extensive Northern Hemisphere glaciation.

Early Proterozoic climates and plate motions inferred from major element chemistry of lutites

1982-10-01

H.W. Nesbitt , Grant M. Young

Variation of O18 content of waters from natural sources

1953-11-01

Samuel Epstein , T. K. Mayeda

The ICS International Chronostratigraphic Chart

2013-09-01

K.M. Cohen , Stanley C. Finney , P.L. Gibbard +1 more

The International Commission on Stratigraphy (ICS) has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of … The International Commission on Stratigraphy (ICS) has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of their boundaries. The primary objective of ICS is to define precisely a global standard set of time-correlative units (Systems, Series, and Stages) for stratigraphic successions worldwide. These units are, in turn, the basis for the Periods, Epochs and Ages of the Geological Time Scale. Setting an international global standard is fundamental for expressing geological knowledge. It is also of considerable pragmatic importance as it provides the framework through which regional-scale higher-resolution divisions can be linked, equated and collated. This is a status update on the International Chronostratigraphic Chart and the ICS website www.stratigraphy.org.

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Orbital and Millennial Antarctic Climate Variability over the Past 800,000 Years

2007-07-06

J. Jouzel , Valérie Masson‐Delmotte , Olivier Cattani +7 more

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage … A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, â¼800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.

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The calculation of lead-210 dates assuming a constant rate of supply of unsupported 210Pb to the sediment

1978-04-01

P. G. Appleby , Frank Oldfield

A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations

1973-03-01

T. E. Krogh

A High-Resolution Absolute-Dated Late Pleistocene Monsoon Record from Hulu Cave, China

2001-12-14

Yujia Wang , Hai Cheng , R. Lawrence Edwards +4 more

Oxygen isotope records of five stalagmites from Hulu Cave near Nanjing bear a remarkable resemblance to oxygen isotope records from Greenland ice cores, suggesting that East Asian Monsoon intensity changed … Oxygen isotope records of five stalagmites from Hulu Cave near Nanjing bear a remarkable resemblance to oxygen isotope records from Greenland ice cores, suggesting that East Asian Monsoon intensity changed in concert with Greenland temperature between 11,000 and 75,000 years before the present (yr. B.P.). Between 11,000 and 30,000 yr. B.P., the timing of changes in the monsoon, as established with 230Th dates, generally agrees with the timing of temperature changes from the Greenland Ice Sheet Project Two (GISP2) core, which supports GISP2's chronology in this interval. Our record links North Atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer East Asian Monsoon originates.

Sea level and global ice volumes from the Last Glacial Maximum to the Holocene

2014-10-13

Kurt Lambeck , Hélène Rouby , Anthony Purcell +2 more

Significance Several areas of earth science require knowledge of the fluctuations in sea level and ice volume through glacial cycles. These include understanding past ice sheets and providing boundary conditions … Significance Several areas of earth science require knowledge of the fluctuations in sea level and ice volume through glacial cycles. These include understanding past ice sheets and providing boundary conditions for paleoclimate models, calibrating marine-sediment isotopic records, and providing the background signal for evaluating anthropogenic contributions to sea level. From ∼1,000 observations of sea level, allowing for isostatic and tectonic contributions, we have quantified the rise and fall in global ocean and ice volumes for the past 35,000 years. Of particular note is that during the ∼6,000 y up to the start of the recent rise ∼100−150 y ago, there is no evidence for global oscillations in sea level on time scales exceeding ∼200 y duration or 15−20 cm amplitude.

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A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation

1989-12-01

Richard G. Fairbanks

Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol

2000-02-01

Andrew Murray , A.G. Wintle

A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates

1997-11-14

Gérard C. Bond , William J. Showers , Maziet Cheseby +7 more

Evidence from North Atlantic deep sea cores reveals that abrupt shifts punctuated what is conventionally thought to have been a relatively stable Holocene climate. During each of these episodes, cool, … Evidence from North Atlantic deep sea cores reveals that abrupt shifts punctuated what is conventionally thought to have been a relatively stable Holocene climate. During each of these episodes, cool, ice-bearing waters from north of Iceland were advected as far south as the latitude of Britain. At about the same times, the atmospheric circulation above Greenland changed abruptly. Pacings of the Holocene events and of abrupt climate shifts during the last glaciation are statistically the same; together, they make up a series of climate shifts with a cyclicity close to 1470 ± 500 years. The Holocene events, therefore, appear to be the most recent manifestation of a pervasive millennial-scale climate cycle operating independently of the glacial-interglacial climate state. Amplification of the cycle during the last glaciation may have been linked to the North Atlantic's thermohaline circulation.

OPTICAL DATING OF SINGLE AND MULTIPLE GRAINS OF QUARTZ FROM JINMIUM ROCK SHELTER, NORTHERN AUSTRALIA: PART I, EXPERIMENTAL DESIGN AND STATISTICAL MODELS*

1999-08-01

R. F. Galbraith , Richard G. Roberts , G.M. Laslett +2 more

Jinmium rock shelter is famous for the claims made by Fullagar et al. (1996) for the early human colonization and ancient rock art of northern Australia. These claims were based … Jinmium rock shelter is famous for the claims made by Fullagar et al. (1996) for the early human colonization and ancient rock art of northern Australia. These claims were based on thermo‐luminescence ages obtained for the artefact‐bearing quartz sediments that form the floor deposit at the site. In this paper, we outline the background to the optical dating programme at Jinmium, and describe the experimental design and statistical methods used to obtain optical ages from single grains of quartz sand. The results, interpretations, and implications of this dating programme are reported in a companion paper (Roberts et al. 7999, this volume).

GLOBAL GLACIAL ISOSTASY AND THE SURFACE OF THE ICE-AGE EARTH: The ICE-5G (VM2) Model and GRACE

2004-04-21

W. R. Peltier

▪ Abstract The 100 kyr quasiperiodic variation of continental ice cover, which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of Earth history, … ▪ Abstract The 100 kyr quasiperiodic variation of continental ice cover, which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of Earth history, has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n-body effects in the Solar System on the geometry of Earth's orbit around the Sun. The impacts of the changing surface ice load upon both Earth's shape and gravitational field, as well as upon sea-level history, have come to be measurable using a variety of geological and geophysical techniques. These observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid Earth and on the detailed spatiotemporal characteristics of glaciation history. This review focuses upon the most recent advances that have been achieved in each of these areas, advances that have proven to be central to the construction of the refined model of the global process of glacial isostatic adjustment, denoted ICE-5G (VM2). A significant test of this new global model will be provided by the global measurement of the time dependence of the gravity field of the planet that will be delivered by the GRACE satellite system that is now in space.

Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present

2001-04-27

James C. Zachos , Mark Pagani , Lisa C. Sloan +2 more

Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which are now coming to light through investigations of deep-sea sediment … Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which are now coming to light through investigations of deep-sea sediment cores. This evolution includes gradual trends of warming and cooling driven by tectonic processes on time scales of 10(5) to 10(7) years, rhythmic or periodic cycles driven by orbital processes with 10(4)- to 10(6)-year cyclicity, and rare rapid aberrant shifts and extreme climate transients with durations of 10(3) to 10(5) years. Here, recent progress in defining the evolution of global climate over the Cenozoic Era is reviewed. We focus primarily on the periodic and anomalous components of variability over the early portion of this era, as constrained by the latest generation of deep-sea isotope records. We also consider how this improved perspective has led to the recognition of previously unforeseen mechanisms for altering climate.

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Holocene climate variability

2004-10-21

Paul A. Mayewski , Eelco J. Rohling , J. Curt Stager +7 more

Although the dramatic climate disruptions of the last glacial period have received considerable attention, relatively little has been directed toward climate variability in the Holocene (11,500 cal yr B.P. to … Although the dramatic climate disruptions of the last glacial period have received considerable attention, relatively little has been directed toward climate variability in the Holocene (11,500 cal yr B.P. to the present). Examination of ?50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000"8000, 6000"5000, 4200"3800, 3500"2500, 1200"1000, and 600"150 cal yr B.P. Most of the climate change events in these globally distributed records are characterized by polar cooling, tropical aridity, and major atmospheric circulation changes, although in the most recent interval (600"150 cal yr B.P.), polar cooling was accompanied by increased moisture in some parts of the tropics. Several intervals coincide with major disruptions of civilization, illustrating the human significance of Holocene climate variability.

Southward Migration of the Intertropical Convergence Zone Through the Holocene

2001-08-17

Gerald H. Haug , Konrad A Hughen , Daniel M. Sigman +2 more

Titanium and iron concentration data from the anoxic Cariaco Basin, off the Venezuelan coast, can be used to infer variations in the hydrological cycle over northern South America during the … Titanium and iron concentration data from the anoxic Cariaco Basin, off the Venezuelan coast, can be used to infer variations in the hydrological cycle over northern South America during the past 14,000 years with subdecadal resolution. Following a dry Younger Dryas, a period of increased precipitation and riverine discharge occurred during the Holocene "thermal maximum." Since approximately 5400 years ago, a trend toward drier conditions is evident from the data, with high-amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the "Little Ice Age." These regional changes in precipitation are best explained by shifts in the mean latitude of the Atlantic Intertropical Convergence Zone (ITCZ), potentially driven by Pacific-based climate variability. The Cariaco Basin record exhibits strong correlations with climate records from distant regions, including the high-latitude Northern Hemisphere, providing evidence for global teleconnections among regional climates.

A long-term numerical solution for the insolation quantities of the Earth

2004-11-23

J. Laskar , Philippe Robutel , F. Joutel +3 more

We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from -250 Myr to 250 Myr. This solution has been improved with respect … We present here a new solution for the astronomical computation of the insolation quantities on Earth spanning from -250 Myr to 250 Myr. This solution has been improved with respect to La93 (Laskar et al. [CITE]) by using a direct integration of the gravitational equations for the orbital motion, and by improving the dissipative contributions, in particular in the evolution of the Earth–Moon System. The orbital solution has been used for the calibration of the Neogene period (Lourens et al. [CITE]), and is expected to be used for age calibrations of paleoclimatic data over 40 to 50 Myr, eventually over the full Palaeogene period (65 Myr) with caution. Beyond this time span, the chaotic evolution of the orbits prevents a precise determination of the Earth's motion. However, the most regular components of the orbital solution could still be used over a much longer time span, which is why we provide here the solution over 250 Myr. Over this time interval, the most striking feature of the obliquity solution, apart from a secular global increase due to tidal dissipation, is a strong decrease of about 0.38 degree in the next few millions of years, due to the crossing of the resonance (Laskar et al. [CITE]). For the calibration of the Mesozoic time scale (about 65 to 250 Myr), we propose to use the term of largest amplitude in the eccentricity, related to , with a fixed frequency of /yr, corresponding to a period of 405 000 yr. The uncertainty of this time scale over 100 Myr should be about , and over the full Mesozoic era.

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Age Dating and the Orbital Theory of the Ice Ages: Development of a High-Resolution 0 to 300,000-Year Chronostratigraphy

1987-01-01

Douglas G. Martinson , Nicklas G Pisias , James D Hays +3 more

Abstract Using the concept of “orbital tuning”, a continuous, high-resolution deep-sea chronostratigraphy has been developed spanning the last 300,000 yr. The chronology is developed using a stacked oxygen-isotope stratigraphy and … Abstract Using the concept of “orbital tuning”, a continuous, high-resolution deep-sea chronostratigraphy has been developed spanning the last 300,000 yr. The chronology is developed using a stacked oxygen-isotope stratigraphy and four different orbital tuning approaches, each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data. Each approach yields a separate chronology. The error measured by the standard deviation about the average of these four results (which represents the “best” chronology) has an average magnitude of only 2500 yr. This small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used. Excellent convergence between chronologies developed using each of five different paleoclimatological indicators (from a single core) is also obtained. The resultant chronology is also insensitive to the specific indicator used. The error associated with each tuning approach is estimated independently and propagated through to the average result. The resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr, in excellent agreement with the 2500-yr estimate. Transfer of the final chronology to the stacked record leads to an estimated error of ±1500 yr. Thus the final chronology has an average error of ±5000 yr.

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High-resolution carbon dioxide concentration record 650,000–800,000 years before present

2008-05-01

Dieter Lüthi , Martine Floch , Bernhard Bereiter +7 more

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The Phanerozoic Record of Global Sea-Level Change

2005-11-25

Kenneth G. Miller , Michelle A. Kominz , James V. Browning +7 more

We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). … We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). Long-term sea level peaked at 100 +/- 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred. Sea level mirrors oxygen isotope variations, reflecting ice-volume change on the 10(4)- to 10(6)-year scale, but a link between oxygen isotope and sea level on the 10(7)-year scale must be due to temperature changes that we attribute to tectonically controlled carbon dioxide variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry, and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past 100 My, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5 Ma to the present).

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Intcal04 Terrestrial Radiocarbon Age Calibration, 0–26 Cal Kyr BP

2004-01-01

Paula Reimer , Mgl Baillie , Édouard Bard +7 more

A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP … A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0–26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0–12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4–26.0 cal kyr B P. A substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the 14 C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief, but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue).

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Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica

1999-06-01

Jean‐Robert Petit , J. Jouzel , Dominique Raynaud +7 more

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Eight glacial cycles from an Antarctic ice core

2004-06-01

Laurent Augustin , Carlo Barbante , Piers R. F. Barnes +7 more

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ATMOSPHERIC TELECONNECTIONS FROM THE EQUATORIAL PACIFIC1

1969-03-01

J. Bjerknes

The “high index” response of the northeast Pacific westerlies to big positive anomalies of equatorial sea temperature, observed in the winter of 1957–58, has been found to repeat during the … The “high index” response of the northeast Pacific westerlies to big positive anomalies of equatorial sea temperature, observed in the winter of 1957–58, has been found to repeat during the major equatorial sea temperature maxima in the winters of 1963–64 and 1965–66. The 1963 positive temperature anomaly started early enough to exert the analogous effect on the atmosphere of the south Indian Ocean during its winter season. The maxima of the sea temperature in the eastern and central equatorial Pacific occur as a result of anomalous weakening of the trade winds of the Southern Hemisphere with inherent weakening of the equatorial upwelling. These anomalies are shown to be closely tied to the “Southern Oscillation” of Sir Gilbert Walker.

The Trophic‐Dynamic Aspect of Ecology

1942-10-01

Raymond L. Lindeman

The biomass distribution on Earth

2018-05-21

Yinon M. Bar-On , Rob Phillips , Ron Milo

Significance The composition of the biosphere is a fundamental question in biology, yet a global quantitative account of the biomass of each taxon is still lacking. We assemble a census … Significance The composition of the biosphere is a fundamental question in biology, yet a global quantitative account of the biomass of each taxon is still lacking. We assemble a census of the biomass of all kingdoms of life. This analysis provides a holistic view of the composition of the biosphere and allows us to observe broad patterns over taxonomic categories, geographic locations, and trophic modes.

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The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

2020-08-01

Paula Reimer , William E. N. Austin , Édouard Bard +7 more

ABSTRACT Radiocarbon ( 14 C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating … ABSTRACT Radiocarbon ( 14 C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14 C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14 C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14 C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14 C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14 C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

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IntCal09 and Marine09 Radiocarbon Age Calibration Curves, 0–50,000 Years cal BP

2009-01-01

Paula Reimer , M. G. L. Baillie , Édouard Bard +7 more

The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to … The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14 C and calendar timescales as established in 2002. No change was made to the curves from 0–12 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and are available in the Supplemental Material at www.radiocarbon.org .

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IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0–50,000 Years cal BP

2013-01-01

Paula Reimer , Édouard Bard , Alex Bayliss +7 more

The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14 C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. … The IntCal09 and Marine09 radiocarbon calibration curves have been revised utilizing newly available and updated data sets from 14 C measurements on tree rings, plant macrofossils, speleothems, corals, and foraminifera. The calibration curves were derived from the data using the random walk model (RWM) used to generate IntCal09 and Marine09, which has been revised to account for additional uncertainties and error structures. The new curves were ratified at the 21st International Radiocarbon conference in July 2012 and are available as Supplemental Material at www.radiocarbon.org. The database can be accessed at http://intcal.qub.ac.uk/intcal13/.

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Foraminiferal Genera and Their Classification

1988-01-01

Alfred R. Loeblich , Helen Tappan

Traversing the Kuroshio: Paleolithic migration across one of the world’s strongest ocean currents

2025-06-25

Yu-Lin K. Chang , Yasumasa Miyazawa , Xinyu Guo +3 more | Science Advances

The maritime migration to the South Ryukyu Islands of southwestern Japan, which occurred approximately 30,000 years ago, was one of the most difficult sea crossings accomplished by the Late Pleistocene … The maritime migration to the South Ryukyu Islands of southwestern Japan, which occurred approximately 30,000 years ago, was one of the most difficult sea crossings accomplished by the Late Pleistocene Homo sapiens. This study performs numerical simulations to investigate the conditions that were needed to cross between Taiwan and Yonaguni Island, where one of the world's strongest ocean currents, the Kuroshio, remains active. We combined simulations based on three ocean models with data from an actual experimental voyage conducted in 2019. The results showed that travel across this sea would have been possible on both the modern and Late Pleistocene oceans if a dugout canoe was used with a suitable departure place and paddling strategy. Recognizing the Kuroshio, paddling to counteract this current, and using high-level navigation were crucial to success. This suggests that the Paleolithic maritime expansion in the Western Pacific involved both advanced technologies and strategic challenges.

Headward incision of large rivers in response to glacial sea level fall

2025-06-25

Zhongping Lai , Yuexin Liu , Z.Y. Wu +3 more | Science Advances

Sea level change is an important forcing on lowland fluvial systems. Although its impact is suggested to extend up to hundreds of kilometers inland, this impact is often considered confined … Sea level change is an important forcing on lowland fluvial systems. Although its impact is suggested to extend up to hundreds of kilometers inland, this impact is often considered confined to deltaic regions. We present luminescence dating of cores from the Jianghan Plain in the middle Yangtze River that demonstrates the influence of the last glacially driven sea level fall extended over 1000-kilometers inland. Luminescence ages reveal a common sedimentary hiatus from ~26 to ~17 thousand years ago (ka), reflecting fluvial incision of >35 meters triggered by sea level fall. Subsequent rapid aggradation occurred within these incised valleys during deglaciation between ~17 and ~9 ka and then slowed down afterward. A further synthesis on global continental rivers shows that sea level change affects large, low-gradient lowland fluvial systems farther upstream than generally recognized, with postperturbation geomorphologic equilibrium reachable in timescales comparable to the length of Quaternary glacial cycles.

CO2 and summer insolation as drivers for the Mid-Pleistocene Transition

2025-06-24

Meike D. W. Scherrenberg , Constantijn J. Berends , Roderik S. W. van de Wal | Climate of the past

Abstract. During the Mid-Pleistocene Transition (MPT; ∼ 1.2–0.8 Myr ago) the dominant periodicity of glacial cycles increased from 41 kyr to an average of 100 kyr, without any appreciable change … Abstract. During the Mid-Pleistocene Transition (MPT; ∼ 1.2–0.8 Myr ago) the dominant periodicity of glacial cycles increased from 41 kyr to an average of 100 kyr, without any appreciable change in the orbital pacing. As the MPT is not a linear response to orbital forcing, it must have resulted from feedback processes in the Earth system. However, the precise mechanisms underlying the transition are still under debate. In this study, we investigate the MPT by simulating the Northern Hemisphere ice-sheet evolution over the past 1.5 Myr. The transient climate forcing of the ice-sheet model was obtained using a matrix method, by interpolating between two snapshots of global climate model simulations. Changes in climate forcing are caused by variations in CO2 and insolation, as well as implicit climate–ice-sheet feedbacks. Using this method, we were able to capture glacial–interglacial periodicity during the past 1.5 Myr and thereby reproduce the shift from 41 to 100 kyr cycles without any additional drivers. Instead, the modelled frequency change results from the prescribed CO2 combined with orbital forcing and ice-sheet feedbacks. Early Pleistocene terminations are initiated by insolation maxima. After the MPT, low interstadial CO2 levels may compensate insolation maxima which would otherwise favour deglaciation, leading to a longer duration of the glacial cycle. Terminations are also affected by ice volume. If the North American ice sheet is small or very large, it becomes sensitive to small temperature increases. A medium-sized ice sheet is less sensitive through its location and the merger of the Laurentide and Cordilleran ice sheets. Therefore, Late Pleistocene terminations are also facilitated by the large ice-sheet volume, where small changes in temperature lead to self-sustained melt. Additionally, we carried out experiments with constant CO2, where we can capture the 41 kyr cycles and some Late Pleistocene cycles. However, no persistent 100 kyr periodicity is established. Experiments with constant (or evolving) CO2 concentrations did not generate a substantial precession signal in the ice volume. Instead, the frequency is dominated by successful terminations, which are initiated by strong (generally obliquity) insolation maxima. Our results therefore indicate that the glacial cycle periodicity of the past 1.5 Myr can be described by changes in insolation, CO2, and ice-sheet feedback processes and that maintaining low CO2 throughout insolation maxima may prolong glacial cycles.

Environmental changes reflected by sedimentary records of detrital minerals in the eastern Laptev Sea over the past 12 kyrs

2025-06-24

Kunshan Wang , Aleksandr A. Bosin , Dirk Nürnberg +6 more | Quaternary Science Reviews

DATA ON THE UNKNOWN: THE EMBRYO OF IRAQIA SIMPLEX HENSON, 1948 (LARGER BENTHIC FORAMINIFERA; EARLY APTIAN, CENTRAL IRAN)

2025-06-24

Félix Schlagintweit , Koorosh Rashidi , Reza Hanifzadeh | Acta Palaeontologica Romaniae

Iraqia simplex Henson, the type-species of this orbitolinid genus, is classified among the Dictyoconinae Schubert that is principally defined by a simple megalospheric embryo. However, neither the original nor any … Iraqia simplex Henson, the type-species of this orbitolinid genus, is classified among the Dictyoconinae Schubert that is principally defined by a simple megalospheric embryo. However, neither the original nor any later description of the taxon contained any specifications (or illustration) of this taxonomically important feature except that it should be situated eccentrically at the beginning of an early spiral stage. Abundant material from the early Aptian Taft Formation of Central Iran, that is in perfect conformity with Henson’s Iraqi type-material, shows the presence of a simple embryo positioned centrically at the apex of the generally high-conical tests. Apart from other differences in the internal test structure, this feature therefore appears to represent a further distinguishing criterion to the allied genus Orbitolinopsis Henson. The available material also provides a relatively good overview of the so far unknown embryo’s biometric variability. Among the Dictyoconinae, a centric embryo can be considered as the exception rather than the rule.

Landscape and climatic environments of sedimentation during the Late Glacial and Holocene in the lower reaches of the Chernaya River (southeast of the Barents Sea region, Nenets Autonomous Okrug)

2025-06-24

Yu. Golubeva , T. I. Мarchenko-Vagapova | Vestnik of Geosciences

The article presents the results of micropaleontological studies (palynological and diatom analyses), which are traditional in a comprehensive study of geosystems. A coastal outcrop in the estuary area of the … The article presents the results of micropaleontological studies (palynological and diatom analyses), which are traditional in a comprehensive study of geosystems. A coastal outcrop in the estuary area of the Chernaya River was studied. The boulder loam exposed at the base of the section with a visible thickness of about 10 m is correlated with the Polar (Ostashkov) horizon, which is confirmed by the results of OSL dating. The overlying sediments have diagnostic features of flow-till. The results of palynological study of clay sediments in the roof of the section indicate the existence of a small proglacial lake formed during the degradation of Polar glaciation. Later, the reservoir underwent swamping and transformation into a permafrost hummocky peat massif. Peat formation began in the Early Holocene. The process of peat accumulation is dated at 7180±150 14C BP (IGAN 10839) and 5720±100 14C BP (IGAN 10838), respectively. The studied glacial and lake-bog sediments were part of a supraglacial sedimentary complex, the fabric of which included both freshwater proglacial reservoirs and brackish-water basins formed during ingression. At the same time, some different types of lakes were probably isolated from each other by dead ice or ridges of loose rocks, subsequently preserved or destroyed by erosional alluvial processes.

Late Quaternary productivity and hydrographic variability in the upper water column of the Agulhas Return Current region as inferred from planktic foraminifera

2025-06-24

Divya Verma , Pawan Govil , Shailesh Agrawal +3 more | Quaternary International

The Nucleation and Degradation of Pothole Wetlands by Human-Driven Activities and Climate During the Quaternary in a Semi-Arid Region (Southern Iberian Peninsula)

2025-06-24

Alejandro Jiménez‐Bonilla , Inmaculada Expósito , Fernando Gázquez +2 more | Geographies

In this study, we selected a series of pothole wetlands to investigate their nucleation, evolution, and recent anthropogenic degradation in the Alcores Depression (AD), southern Iberian Peninsula, where over 100 … In this study, we selected a series of pothole wetlands to investigate their nucleation, evolution, and recent anthropogenic degradation in the Alcores Depression (AD), southern Iberian Peninsula, where over 100 closed watersheds containing shallow, ephemeral water bodies up to 2 hm2 have been identified. We surveyed the regional geological framework, utilized digital elevation models (DEMs), orthophotos, and aerial images since 1956. Moreover, we analyzed precipitation and temperature data in Seville from 1900 to 2024, collected hydrometeorological data since 1990 and modelled the water level evolution from 2002 to 2025 in a representative pothole in the area. Our observations indicate a flooded surface reduction by more than 90% from the 1950s to 2025. Climatic data reveal an increase in annual mean temperatures since 1960 and a sharp decline in annual precipitation since 2000. The AD’s inception due to tectonic isolation during the Quaternary favoured the formation of pothole wetlands in the floodplain. The reduction in the hydroperiod and wetland degradation was primarily due to agricultural expansion since 1950, which followed an increase in groundwater extraction and altered the original topography. Recently, decreased precipitation has exponentially accelerated the degradation and even the complete disappearance of many potholes. This study underscores the fragility of small wetlands in the Mediterranean basin and the critical role of human management in their preservation. Restoring these ecosystems could be a highly effective nature-based solution, especially in semi-arid climates like southern Spain. These prairie potholes are crucial for enhancing groundwater recharge, which is vital for maintaining water availability in regions with limited precipitation. By facilitating rainwater infiltration into the aquifer, recharge potholes increase groundwater levels. Additionally, they capture and store run-off during heavy rainfall, reducing the risk of flooding and soil erosion. Beyond their hydrological functions, these wetlands provide habitats that support biodiversity and promote ecological resilience, reinforcing the need for their protection and recovery.

What is the influence of centennial evolution from macrophytes to algae on organic matter burial in the upper reaches of Yangtze River from the biomarker carbon isotope fingerprint

2025-06-24

Yan Chen , Jiayu Zhao , Xiangyong Zheng +5 more | Journal of Environmental Management

Effects of Tide-Induced Mixing on the Equator to Pole Surface Temperature Gradient During the Middle Miocene Climate Optimum

2025-06-24

Xinyu Huang , Caixia Wang , Jilin Wei +3 more | Journal of Climate

Abstract Based on reconstructions from proxy records, the Middle Miocene Climate Optimum (MMCO, 16.9–14.7 Ma) was a relatively warm interval of amplified polar warmth and a weaker-than-present equator-to-pole meridional temperature … Abstract Based on reconstructions from proxy records, the Middle Miocene Climate Optimum (MMCO, 16.9–14.7 Ma) was a relatively warm interval of amplified polar warmth and a weaker-than-present equator-to-pole meridional temperature gradient. However, simulating the exact weaker-than-present gradient reconstructed from proxy records is still challenging. Several studies of both past and present oceans have shown that tidal mixing strongly influences climate. However, none of the previous climate simulations of the MMCO have considered the impact of tidal dissipation thus far. This study estimates the tidal dissipation and mixing in the deep ocean during the MMCO using the coupled model FGOALS-g3. A set of sensitivity experiments was conducted to investigate the effects of tidal mixing on the equator-to-pole meridional temperature gradient during the MMCO. The results show that compared to the experiment without tidal mixing, the experiment with tidal mixing featured an increase in the surface air temperature (SAT) of only 0.23°C at low latitudes and as much as 1.98°C at high latitudes during the MMCO, leading to a 1.75°C reduction in the simulated equator-to-pole meridional surface temperature gradient. These results are related to the enhancement of meridional overturning circulation and oceanic meridional heat transport from the equatorial zones to the poles with increasing ocean vertical mixing when tidal mixing is considered. Overall, our study shows that considering tidal mixing can improve the simulation of the meridional temperature gradient during the MMCO, which provides a feasible method for improving the simulation of the MMCO climate.

Rapid relative sea-level fall, 8–6 ka, in the Windmill Islands, East Antarctica

2025-06-24

David Small , Sonja Berg , Duanne White | Quaternary Science Reviews

Toarcian Greenhouse Warming Shifted Climate Belts Poleward With Global Change Implications

2025-06-24

Yan Wang , Micha Ruhl , Jian Cao +4 more | Journal of Geophysical Research Atmospheres

Abstract Atmospheric convection is predicted to change in response to anthropogenic global warming, leading to a poleward expansion of the Hadley cells and associated arid climate belts. The magnitude of … Abstract Atmospheric convection is predicted to change in response to anthropogenic global warming, leading to a poleward expansion of the Hadley cells and associated arid climate belts. The magnitude of possible latitudinal change in the position of climate belts is, however, poorly understood. Here, we address this issue based on a case study of the early Toarcian (late Early Jurassic) Oceanic Anoxic Event (T‐OAE, ∼183 Ma), one of the most significant global change events of the Phanerozoic, characterized by elevated humidity and major disturbances to terrestrial ecosystems on land. We present new leaf‐wax n ‐alkanes δ 13 C data from the high‐paleo‐latitude Junggar Basin (northwest China) spanning the T‐OAE and develop a time–space framework of plant‐fractionation change, from low‐ to high‐paleolatitudes across this time interval. We show that significant latitudinal changes in humidity occurred across the T‐OAE (∼10°), likely because of a significant northward expansion of the low‐latitude arid belts to mid‐paleo‐latitudes, and by inference a latitudinal expansion of the Hadley cells. This has important implications for the anthropogenic global warming and its effects on climate belts.

The glacial paleolandscapes of Southern Africa: the legacy of the Late Paleozoic Ice Age

2025-06-24

Pierre Dietrich , François Guillocheau , Guilhem Amin Douillet +7 more | Earth Surface Dynamics

Abstract. The modern relief of Southern Africa is characterized by stepped plateaus bordered by escarpments. This morphology is thought to result from stepwise uplift and ensuing continental-scale erosion of the … Abstract. The modern relief of Southern Africa is characterized by stepped plateaus bordered by escarpments. This morphology is thought to result from stepwise uplift and ensuing continental-scale erosion of the region as it rode over Africa's mantle superplume following the breakup of Gondwana, i.e., since the mid-Mesozoic. We show in this contribution that the modern topography over large parts of Southern Africa bears glacial relief inherited from the Late Paleozoic Ice Age (LPIA) that occurred between 370 and 280 Myr ago and during which Gondwana – which included Southern Africa – was covered in thick ice masses. Southern Africa hosts vast (up to 106 km2) and thick (up to 5 km) sedimentary basins ranging from the Carboniferous, represented by glaciogenic sediments tied to the LPIA, to the Jurassic–Cretaceous. These basins are separated by intervening regions largely underlain by Archean to Paleoproterozoic cratonic areas that correspond to paleohighlands that preserve much of the morphology that existed when sedimentary basins formed, particularly glacial landforms. In this contribution, we review published field and remote data and provide a new large-scale interpretation of the geomorphology of these paleohighlands of Southern Africa. Our foremost finding is that over Southern Africa vast surfaces are exhumed glacial landscapes tied to the LPIA. These glacial landscapes manifest in the form of centimeter-scale striated pavements; meter-scale fields of roches moutonnées, whalebacks, and crag and tails, narrow gorges cut into mountain ranges; and kilometer-scale glacial erosion surfaces and large U-shaped valleys, overdeepenings, fjords, and troughs up to 200 km in length. These forms are frequently found covered or filled with coarse-grained, glaciogenic sediments (frontal and lateral moraines, grounding zone wedges, IRD-bearing muds, etc.), whose distribution largely follows the pattern of glacial forms. Importantly, these glacial forms still today control many modern aspects of the surficial processes, such as glacial valleys that funnel the modern drainage network of some transects of the main rivers of Southern Africa. To explain how the glacial landscape has survived for such an extended period, we argue that its preservation and modern exposure may be attributed to burial under substantial layers of Karoo sediments and lavas for approximately 120 to 170 million years, followed by its exhumation since the middle Mesozoic, linked to the uplift of Southern Africa. Owing to strong erodibility contrasts between resistant Precambrian bedrock and softer sedimentary infill, the glacial landscapes have been exhumed and re-exposed. This remarkable preservation allows us to reconstruct the paleogeography of Southern Africa in the aftermath of the LPIA, consisting of highlands over which ice masses nucleated and from which they flowed through the escarpments and toward lowlands that now correspond to sedimentary basins. Moreover, we propose that in many instances, glacial erosion processes have superimposed an older, non-glacial land system whose original form is still expressed in the modern geomorphology of Southern Africa. Notably, some escarpments that delineate high-standing plateaus from coastal plains could be surficial expressions of crustal-scale faults whose offset likely operated before the LPIA and on which glacial processes are marked in the form of striae. Additionally, some hill or mountain ranges may have already existed during LPIA times, potentially reflecting remnants of Pan-African orogenic belts. Whether these features were later reactivated or persisted unchanged since that time is uncertain, but they were shaped by glacial erosion. We further propose that a network of pre-existing alluvial valleys could have existed before the LPIA, possibly formed during an extended period of exhumation and erosion in Southern Africa. These valleys may have later facilitated ice flow from highlands to lowlands, although the extent and configuration of such features remain speculative. The exhumed pre-LPIA landforms may in some cases be taken for pediments, pediplains, and pedivalleys and interpreted as recording the topographic evolution of Southern Africa after the dislocation of Gondwana during the Mesozoic. Some glacial valleys are also taken for rift structures. We therefore emphasize the need of considering the legacy of LPIA geomorphology when assessing the topographic evolution of Southern African and its resulting modern aspect, as well as inferences about climate changes and tectonic processes.

Anomalously cool clumped isotope temperatures in tropical lagoon carbonates

2025-06-24

D. Allie Wyman-Feravich , Miquela Ingalls , Jessica L. Conroy +2 more | The Depositional Record

Abstract Carbonate clumped isotopes are a powerful tool for paleoclimate reconstruction due to the ability to reconstruct past changes in both temperature and precipitation‐evaporation balance. Here we test the utility … Abstract Carbonate clumped isotopes are a powerful tool for paleoclimate reconstruction due to the ability to reconstruct past changes in both temperature and precipitation‐evaporation balance. Here we test the utility of this method on last millennium carbonate lagoonal sediments from Kiritimati, a coral atoll where modern climate variability is driven by interannual changes in the El Niño‐Southern Oscillation. We find last millennium lagoonal temperatures from clumped isotopes are cooler than anticipated compared to modern measurements and other paleoclimate reconstructions. This discrepancy is probably due to sediments containing a mixture of high‐magnesium calcite derived from primary precipitates and benthic foraminifera and aragonite derived from warm water corals. We employed an inverse mixing model to minimise the impact of vital effects related to coral growth on clumped isotope compositions and found an increasing difference between modelled and measured T(Δ 47 ) values through time. This potentially indicates that the composition of lagoon water became increasingly unique from the coral carbonate formation waters through the last millennium. This study highlights the necessity of detailed understanding of carbonate mineralogy, sedimentology and provenance in interpreting clumped isotope temperature reconstructions.

A Late Holocene sedimentary record of earthquakes and hydroclimate from Ozette Lake, Washington, USA

2025-06-24

Elana L. Leithold , Karl W. Wegmann , D. R. Bohnenstiehl +2 more | Quaternary Research

Abstract Ozette Lake, located on the Olympic Peninsula of western Washington, is ideally situated to provide a sedimentary record of past earthquakes along the northern portion of the Cascadia subduction … Abstract Ozette Lake, located on the Olympic Peninsula of western Washington, is ideally situated to provide a sedimentary record of past earthquakes along the northern portion of the Cascadia subduction zone. The lake stratigraphy is punctuated by turbidites, with characteristics typical of those triggered by earthquake shaking as seen in other lakes worldwide. Sediments deposited in Ozette Lake over the past 1300 years between earthquake events show decadal-scale variations in color, magnetic susceptibility, clay content, organic carbon content, density, and computed tomography (CT) intensity. Applying the dynamic time warping technique reveals a strong correlation of CT intensity to historical, instrumental measurements of regional cool-season precipitation, indicating that sediments in the lake preserve a high-fidelity record of decadally averaged fluvial sediment discharge and climate. Correlation of CT intensity patterns from older strata preserved deeper in the lake stratigraphy to two independent, regional paleo-precipitation reconstructions similarly suggests that the sediments record decadal variations in hydroclimate. We provide radiocarbon-independent dates for the past four northern Cascadia subduction earthquakes that are within the uncertainty of a radiocarbon age-depth model but are more precisely estimated by placing earthquake-triggered turbidites in the context of wet and dry periods in these tree-ring- and oxygen-isotope-based reconstructions. Paleoclimate-based constraints on the age of event layers in this and other regional lakes have the potential to help address ongoing questions about past ruptures on the Cascadia subduction margin.

Onset of extensive human fire use 50,000 y ago

2025-06-23

S.M. Jiang , Debo Zhao , Stefanie Kaboth‐Bahr +7 more | Proceedings of the National Academy of Sciences

Fire is a pivotal aspect of human involvement in the carbon cycle. However, the precise timing of the large-scale human fire use remains uncertain. Here, we report a pyrogenic carbon … Fire is a pivotal aspect of human involvement in the carbon cycle. However, the precise timing of the large-scale human fire use remains uncertain. Here, we report a pyrogenic carbon record of East Asian fire history over the past 300,000 y from the East China Sea. This record suggests a rapid increase in fire activity since approximately 50,000 y ago, indicating a decoupling from the monsoon climate, and this pattern is consistent with fire histories in Europe, Southeast Asia, and Papua New Guinea-Australia regions. By integrating extensive archaeological data, we propose that the intensified global expansion of modern human and population growth, coupled with the rising demand for fire use during cold glacial periods, resulted in a significant increase in fire utilization from 50,000 y onward. This suggests that a measurable human imprint on the carbon cycle via fire likely predates the Last Glacial Maximum.

Isotopic constraints on the peak of the Early Paleozoic Icehouse

2025-06-23

Joshua B. Zimmt , Kristin Bergmann , Seth Finnegan +3 more | Geological Society of America Bulletin

While the intensification of the Early Paleozoic Icehouse is commonly cited as the main driver of the Late Ordovician mass extinction, we lack high-resolution, stratigraphically constrained climate records to test … While the intensification of the Early Paleozoic Icehouse is commonly cited as the main driver of the Late Ordovician mass extinction, we lack high-resolution, stratigraphically constrained climate records to test this hypothesis. Here, we develop a high-resolution climate record for the Late Ordovician by applying stable isotope geochemistry (δ18O, δ13C; n = 81) and carbonate clumped isotope paleothermometry (Δ47; n = 45) to fossils from the stratigraphically expanded Ellis Bay Formation on Anticosti Island (Canada). Focusing our analysis on fossils that primarily experienced closed-system alteration, we identify two distinct phases of increasing fossil δ18OVPDB values: a moderate increase of 1.0‰−1.5‰ across the Katian/Hirnantian boundary and a larger increase of 2.5‰−4.5‰ in the middle to late Hirnantian. Only the latter is associated with Δ47 evidence for cool tropical sea surface temperatures, and based on its sequence stratigraphic context immediately overlying a regional subaerial unconformity, we interpret this excursion as reflecting the earliest stages of transgression during the waning of the Hirnantian Glacial Maximum. This revises the conclusions of previous paired stable and clumped isotope studies, which argued that the major drop in sea surface temperatures occurred at the Katian/Hirnantian boundary. When integrated with patterns of faunal turnover from Anticosti Island, our conclusion that major tropical cooling and maximum ice volumes did not occur until the middle to late Hirnantian suggests that an apparent pulse of extinction near the Katian/Hirnantian boundary may be in part a stratigraphic artifact generated by widespread glacio-eustically forced unconformities and facies shifts.

Carbonate Profile of Chestnut–Solonetz Associations and Its Anthropogenic Transformation in Arable Land

2025-06-23

N. B. Khitrov , N. G. Kruglyakova , И. Н. Горохова +1 more | Eurasian Soil Science

Multi‐million‐year evolution of the Greenland Ice Sheet in Inglefield Land, North Greenland

2025-06-23

Anne Søndergaard , Jane Lund Andersen , Nicolaj K. Larsen +4 more | Journal of Quaternary Science

ABSTRACT Information on past sensitivity of the Greenland Ice Sheet to climate change is of importance for optimizing models simulating the future evolution of ice mass loss. While the ice‐sheet … ABSTRACT Information on past sensitivity of the Greenland Ice Sheet to climate change is of importance for optimizing models simulating the future evolution of ice mass loss. While the ice‐sheet change during the Lateglacial and Holocene is relatively well constrained, the long‐term (multi‐million‐year) evolution of the Greenland Ice Sheet remains poorly known. In this study, we use in situ cosmogenic 10 Be, 26 Al, and 14 C nuclide concentrations from bedrock in Inglefield Land, western North Greenland, together with Markov chain Monte Carlo inversion to constrain the multi‐million‐year ice sheet history of this area. Our results indicate that the area became ice‐covered for the first time at the beginning of the Quaternary and was glaciated for extensive periods during the Pleistocene. We cannot resolve whether the ice cover was confined to local ice caps or part of a larger ice sheet but only conclude that the ice cover was likely persistent with short interglacials. Further, our results show that the area has been characterized by low erosion rates (<1 m/Myr) during the past million years, suggesting cold‐based ice similar to today's conditions.

Biosignatures of an ancient bedrock- and impact structure-hosted deep biosphere: current knowledge and future perspectives

2025-06-23

J. Gustafsson , Henrik Drake | Discover Geoscience

Hydroclimatic development from the Early Holocene to anthropogenic times: a comparative study of diatom oxygen isotope records and multiproxy data from Lake Khamra, eastern Siberia

2025-06-23

Amelie Stieg , Boris K. Biskaborn , Ulrike Herzschuh +4 more | Boreas

Northern Eurasia underwent major hydroclimatic changes since the beginning of the Holocene interglacial. A rapid warming period reaching the Holocene Thermal Maximum (HTM), followed by a general cooling trend until … Northern Eurasia underwent major hydroclimatic changes since the beginning of the Holocene interglacial. A rapid warming period reaching the Holocene Thermal Maximum (HTM), followed by a general cooling trend until recent times, was observed in Eurasian lacustrine diatom oxygen isotope (δ 18 O diatom ) records. In this study, we present a new Holocene δ 18 O diatom record from Lake Khamra (59.99°N, 112.98°E, Siberia). Our record aligns with Holocene δ 18 O diatom records across the Northern Hemisphere, showing a general millennial‐scale cooling trend following an initial maximum at 11.2 cal. ka BP and a second maximum at 6.7 cal. ka BP. These maxima correspond to the summer insolation maximum and elevated Northern Hemisphere air temperatures, as well as increased bioproductivity. Variability on centennial scales is likely driven by precipitation changes, which coincide with higher sedimentation rates and overlay the general decreasing trend throughout the Holocene. In addition, we compared two multiproxy datasets with decadal resolution from Lake Khamra, including δ 18 O diatom data and biogeochemical proxies such as total organic carbon (TOC), total nitrogen (TN), stable carbon (δ 13 C) and nitrogen (δ 15 N) isotopes, and total mercury (THg). The datasets cover a ~210‐year period ( c . 6.140–6.350 cal. ka BP) at the end of the HTM and a recently published ~220‐year record ( c . 1790–2015 CE) that embraces the anthropogenic times. The comparison of these two warm phases reveals distinct differences in both the absolute values and the variability of the records. Regarding the δ 18 O diatom data, the recent period shows a nearly threefold increase in range and double the standard deviation, suggesting greater hydroclimatic variability compared to the end of the HTM. Notably, THg levels indicate a sharp increase in recent decades, while δ 13 C declined, contrasting with the observations at the end of the HTM. We attribute these observations partially to far‐reaching anthropogenic effects on remote lake systems.

Application and comparison of chronostratigraphic methods for dating eolian deposits

2025-06-23

Chaoqin Chen , Zhongshi Zhang , Zhengtang Guo +4 more | Science China Earth Sciences

Vegetation and environmental dynamics in the central part of the Kola Peninsula during the past 13.3 ka as reflected by ancient plant DNA on sediments from Lake Imandra

2025-06-23

Anastasia Poliakova , Matthias Lenz , Martin Melles +3 more | Journal of Quaternary Science

ABSTRACT The first high‐resolution reconstruction of the vegetation and environmental changes during the last ca 13 300 cal a BP in the central part of the Kola Peninsula (NW Russia) … ABSTRACT The first high‐resolution reconstruction of the vegetation and environmental changes during the last ca 13 300 cal a BP in the central part of the Kola Peninsula (NW Russia) was reconstructed based on sedimentary ancient DNA ( sed aDNA) metabarcoding on sediment core Co1410 from Lake Imandra. In total, 204 taxa known from modern flora are identified. The resulting sequences were assigned to vascular plants (87%), bryophytes (12%), and algae (1%). About half (111 taxa, 49%) are identified at the species level. They belong to 150 genera and 86 families. So far, this is the most diverse and taxonomically detailed palaeoflora described for the Late Pleistocene–Holocene of the Kola Peninsula and North‐European Russia. Sed aDNA studies suggest that the vegetation cover in the region developed from (1) plant colonisation of the study area after the glacier retreated during the Allerød warming at ca 13 300–13 000 a BP to (2) Younger Dryas cold period with re‐entering of the glaciers in the catchment of the Grater (Bolshaya) Imandra and establishing of the steppe–tundra communities. (3) Warming and increasing in vegetation diversity during the Early Holocene, with the formation of the birch forests by the end of this time zone. (4) Mid‐Holocene temperature maximum is correlated with the highest regional plant diversity and a pronounced role of the thermophilic taxa, that is, Lonicera species, Prunus padus, Populus tremula, Sorbus sp./Cotoneaster sp. The highest so far revealed regional diversity of the higher spore plants (10) and aquatic plants (23) is evidenced. Mixed deciduous and coniferous forests were established in the research area during this period, and a drop in plant diversity occurred afterwards. (5) During the Late Holocene, modern communities are formed with a slight increase in biodiversity because of increasing input from cultural plants and weeds. Human impact is clearly diagnosed after 250 a BP, indicated by the presence of Ribes sp., Hypericum sp., and Mentha arvensis as well as eutrophic weeds, that is, Trifolium sp. and Urtica dioica . In addition, this study revealed the past dynamics of some plants rare for the Murmansk region, namely Pteridium aquilinum, with its maximum of occurrence at ca 11 000–8000 cal a BP and a strong decrease thereafter, and Nuphar sp./ Nymphaea sp. occurring regularly since ca 7700 cal a BP and eliminating from the record after ca 3500 cal a BP.

Origin of interstitial water beneath the continental shelf offshore northwestern Australia: insights from hydrogen and oxygen isotope compositions

2025-06-23

Kosuke Yoshii , Hideko Takayanagi , Toshihiro Miyajima +3 more | Progress in Earth and Planetary Science

Late Holocene overflow floods of the Yellow River led to the shrinkage of downstream lakes

2025-06-23

Guansheng Ma , Niannian Fan , Michael Storozum +3 more | Research Square (Research Square)

<title>Abstract</title> During the late Holocene, frequent floods and diversions of the lower Yellow River changed river-lake relationships, with far-reaching effects on the North China Plain's physical and social geography. Current … <title>Abstract</title> During the late Holocene, frequent floods and diversions of the lower Yellow River changed river-lake relationships, with far-reaching effects on the North China Plain's physical and social geography. Current understanding of historical lower Yellow River flood-lake relationships relies predominantly on historical evidence, lacking sufficient sedimentological verification. This paper analyzes sediments from paleo-Dayeze Lake, a major paleolake downstream, and correlate findings with available historical documents. The results indicates that, firstly, the three major overflow flood events of the Yellow River documented in historical literature, e.g., during Emperor Hanwu, the Five Dynasties and early Ming Dynasty were well preserved in the deposits of paleo-Dayeze Lake area, especially, the 800 years relative stable state of the Yellow River following Jing Wang’s regulation at 69-70CE from historical literatures, was supported by the deposits. Secondly, the sediment of the Yellow River became much coarser after Song Dynasty, and after this period the overflowed area from the Yellow River flood could become sandy land. The research confirms the diversion and overflow of the Yellow River drove paleo-Dayeze Lake's evolution and underscores the value of integrating historical and geological evidence for studying river-lake system history.

Initial Discoveries from the Rhizoliths Petrified Forest of Chania

2025-06-22

Emmanouil Manoutsoglou | Heritage

This study presents the initial scientific characterization of the recently discovered Rhizoliths Petrified Forest of Chania, located at Stavros in the Akrotiri peninsula of Crete, Greece. Unlike most known petrified … This study presents the initial scientific characterization of the recently discovered Rhizoliths Petrified Forest of Chania, located at Stavros in the Akrotiri peninsula of Crete, Greece. Unlike most known petrified forests that primarily preserve tree trunks, this site uniquely features an abundance of rhizoliths—fossilized root systems preserved through calcium carbonate mineralization. The rhizoliths exist within aeolianite formations along the coastal front, with diverse morphologies and sizes ranging from small trace-like forms to massive, branched structures exceeding one meter in length. The rhizoliths are exposed within historic Venetian quarries that operated from Minoan times through the medieval period at Stavros Bay, where quarrying operations have revealed these fossilized root systems preserved in coastal dune deposits. The site also contains in situ petrified trunks, calcrete formations, and biokarstic dissolution features that further enhance its scientific value. Microscopic examination of rhizolith samples has revealed valuable information about their internal structure, showing clear biogenic characteristics. The preservation of rhizolith structures and associated sedimentary features provides valuable insight into the Quaternary paleoenvironment, including former vegetation patterns, soil stabilization processes, and paleoclimatic conditions. The alternating layers of aeolianites and paleosols suggest cyclical environmental changes, with periods of active dune formation alternating with more stable conditions allowing soil development and vegetation establishment. This study documents the Stavros rhizoliths and their paleoenvironmental significance, contributing to the comparative understanding of similar features documented at other global sites.

Late Neogene-Quaternary multi-proxy records of prolonged El Niño (El Padre) variability: Implications on tropical eastern Indian Ocean paleoclimate and palaeoceanography

2025-06-21

A. SINGH , Devesh K. Sinha , Kaushik Baruah +1 more | Journal of the Palaeontological Society of India

The Earth’s climate has many rhythms and pulses and behaves differently on longer and shorter scales depending on the changing boundary conditions. Contrasting climatic shifts on short time scales often … The Earth’s climate has many rhythms and pulses and behaves differently on longer and shorter scales depending on the changing boundary conditions. Contrasting climatic shifts on short time scales often characterise the long-term mean state of the Climate. The Tropical Pacific Mean State climate has been alternatively dominated by El Niño-like and La Niña-like conditions. Long-term El Niño-like conditions have been termed permanent El Niño, El Niño State, or El Padre (EP), spanning several thousand years. The Western Pacific Warm Pool (WPWP) responds to EP conditions by changing upper ocean hydrography. We used depth-stratified planktic foraminiferal relative abundance to characterise the changing hydrography of the WPWP over the last 6 million years and its impact on the variability of the strength of the Leeuwin Current (LC) in the Eastern Indian Ocean, which the WPWP influences via the Indonesian throughflow (ITF). Six EP events centred around 6.2-6.0 Ma, 3.6 Ma, 2.8 Ma, 2.3-2.3 Ma, 1.8 Ma and 0.4 Ma have been detected. These EP events are bridged by La Niña State-1 (6.0-4.2 Ma), La Niña State-2 (3.0 Ma), La Niña State-3 (2.6-2.0 Ma) and La Niña State-4 (1.4-1.0 Ma) events. The effect of the EP event in the Eastern Indian Ocean has been transmitted through the ITF, affecting the strength of the LC. The most influential EP events affecting the Eastern Indian Ocean have been EP-3, EP-4, EP-5 and EP-6. In general, the Eastern Indian Ocean responds to the EP events with a general reduction in the strength of the LC.

A Nutrient Effect on the TEX86 Paleotemperature Proxy

2025-06-21

Ronnakrit Rattanasriampaipong , Jessica E. Tierney , Jordan T. Abell +1 more | Geophysical Research Letters

Abstract The paleotemperature proxy is widely used to reconstruct ocean surface temperatures over the past 100 million years. However, archaeal culture experiments show that nutrient stress elevates values by increasing … Abstract The paleotemperature proxy is widely used to reconstruct ocean surface temperatures over the past 100 million years. However, archaeal culture experiments show that nutrient stress elevates values by increasing glycerol dialkyl glycerol tetraether (GDGT) cyclization. Here, we demonstrate that this “nutrient effect” is also recorded in sedimentary GDGTs. Using an expanded core‐top database, we find a significant negative correlation between and nitrate concentrations ( = −0.31; P 0.001) once the thermal effect is removed. There are stronger correlations ( −0.73 to −0.91; P 0.001) in regions with steep nitrate gradients. Comparisons between and ‐based reconstructions from the Arabian Sea and Tasman Sea suggest that nutrient stress influenced GDGT distributions during glacial‐interglacial cycles. Our findings underscore the need to account for nutrient effects when applying paleothermometry.

Fundamentally unchanged northwestern African rainfall regimes across the Plio-Pleistocene transition

2025-06-20

Bryce Mitsunaga , Amy Jewell , Solana Buchanan +4 more | Science Advances

Northern African climate is characterized by strongly contrasting wet summers and dry winters. Dust exported by the northeasterly trade (Harmattan) winds creates marine sedimentary records that have been long interpreted … Northern African climate is characterized by strongly contrasting wet summers and dry winters. Dust exported by the northeasterly trade (Harmattan) winds creates marine sedimentary records that have been long interpreted to show that northern African climate became drier and more variable across the Pliocene-Pleistocene boundary [2.58 million years ago (Ma)], when global climate cooled and high-latitude glacial-interglacial cycles intensified. However, questions about the impact of summer rainfall on winter dust fluxes and thus the history of the African summer monsoons remain. We present a leaf wax hydrogen isotope record from offshore northwestern Africa that demonstrates that rainfall regimes remained stable and varied solely in response to 21,000-year cycles in summer insolation from 3.5 to 2.5 Ma. We infer that the summer rains and winter winds respond to different climate forcings, with summer rainfall driven by solar radiation over the northern African landmass and the winter trades affected by high-latitude climate and meridional temperature gradients.

Humans exacerbated wildfires in the NW Patagonian archipelagoes over the last 2700 years

2025-06-20

Patricio I. Moreno , Javiera Videla , Leonardo A. Villacís +1 more | Quaternary Science Reviews

Dust variations in the western North Pacific dominated by the East Asian monsoon

2025-06-20

Ruxi Dou , Jianjun Zou , Xuefa Shi +7 more | Science China Earth Sciences

Indian monsoon modes and their linkage with precipitation in the Andaman Sea region late Quaternary planktic foraminiferal records

2025-06-20

P. Nayak , A. SINGH , K. Mallick +4 more | Journal of the Palaeontological Society of India

The Late Quaternary variability of the Indian monsoonal winds, both the southwest monsoon (SWM) and the northeast monsoon (NEM), has affected the hydrography of the Andaman Sea region through precipitation … The Late Quaternary variability of the Indian monsoonal winds, both the southwest monsoon (SWM) and the northeast monsoon (NEM), has affected the hydrography of the Andaman Sea region through precipitation and river discharge. The Indian monsoon strength variability has been frequently linked to factors like Northern Hemisphere cooling, sunspot cycle, and glacial-interglacial intervals, besides various other forcing factors, including the shifting position of the Intertropical Convergence Zone (ITCZ), El Niño Southern Oscillation, and Indian Ocean Dipole. The palaeomonsoon proxies have been mainly directed to understand the Wind Strength variability resulting in upwelling in the Arabian Sea or precipitation records from land-based sections. The article addresses an intriguing question about the relationship between Wind Strength Record and the resulting river discharge and precipitation record in the Andaman Sea region. The distinctive feature of the Andaman Sea water masses is the seasonal variations in the inventory of river water discharge, which affects the surface ocean salinity besides local precipitation in the region. Here, we used water mass-sensitive, and depth-stratified planktic foraminiferal assemblages from deep-sea sediment core SK 234-60 in the Andaman Sea region to reconstruct the variability of the Indian monsoonal precipitation during the late Quaternary. The wide distribution of planktic foraminiferal assemblages and their oxygen isotope analysis in deep-sea sediment cores helps to understand the precipitation and water mass conditions, as the temperature, salinity, nutrients, and trophic conditions are primarily affected by river discharge into the Andaman Sea, besides local precipitation. A detailed faunal census counts data for water mass-sensitive planktic foraminifera from the core SK 234-60 raised from the Andaman Sea has been interpreted. The depth-stratified assemblages include mixed layer dwelling (MLD) species, thermocline dweller species (TDS), and upwelling indicator species (UIS), which reflect productivity. During the late Quaternary, we observed six intervals of strengthening of the SWM mode designated here as Southwest Monsoon Mode Increase (SWMMI-1-6), suggested by the higher relative abundance of MLD and very low abundance of Thermocline Dwellers. We have also noticed six intervals of decreased Southwest Monsoon Mode, which is designated here as Southwest Monsoon Mode Decrease (SWMMD-1-6) during the last 25 KyBP. An increase in Northeast Monsoon Mode is abbreviated here as NEMMI, and a decrease in Northeast Monsoon Mode is abbreviated as NEMMD. An interesting finding is the sudden increase in the population of MLD planktic foraminifera just after all four volcanic ash layers from Barren Island during the last 25 KyBP, which might have affected the local rainfall in the Andaman Sea region.

Luminescence dating of palaeoshoreline deposits from Khyargas Nuur, Western Mongolia: A comparative study of multigrain and single‐grain K‐feldspar dating

2025-06-20

Neda Rahimzadeh , Dennis Wolf , Sumiko Tsukamoto +2 more | Journal of Quaternary Science

ABSTRACT The evolution of lakes in western Mongolia and their responses to climate changes and glacial meltwater input remain poorly understood. This study evaluates the reliability of multigrain and single‐grain … ABSTRACT The evolution of lakes in western Mongolia and their responses to climate changes and glacial meltwater input remain poorly understood. This study evaluates the reliability of multigrain and single‐grain K‐feldspar post‐infrared infrared stimulated luminescence (IRSL) (pIRIR) dating applied to palaeoshoreline sediments at Khyargas Nuur, western Mongolia. It specifically focuses on assessing the extent of pIRIR signal bleaching and proposes an improved methodology for dating shoreline sediments where quartz is unsuitable for luminescence dating. Multigrain pIRIR signals measured at 150°C (pIRIR 150 ) and 225°C (pIRIR 225 ) were used to date Holocene and older samples, respectively. Single‐grain pIRIR dating was conducted for the first time in the region to assess bleaching conditions and refine age estimates. Our comprehensive methodological approach was essential for constructing a robust lake level chronology. Single‐grain measurements, combined with the application of the minimum age model (MAM), allowed us to identify and correct for incomplete bleaching in several samples. Notably, many of the multigrain aliquots showed no clear signs of poor bleaching in their equivalent dose ( D e ) distributions, which would have resulted in significant age overestimation if single‐grain data had not been available. Without this approach, the chronology of lake level fluctuations could have been significantly misinterpreted. By addressing this issue, we confidently date the highest lake level at ~129 m above modern lake (a.m.l) to marine isotope stage (MIS) 5 (~89 ka) and a subsequent highstand (~118 m a.m.l) to the Late Glacial (~14 ka). Following this highstand, lake levels declined rapidly (~25 m/ka), reaching ~20 m a.m.l through the Late Glacial to early Holocene transition. During the late Holocene, the palaeolake experienced a gradual regression to ~7 m a.m.l before reaching its current elevation of 1029 m above sea level (a.s.l).

Constraining the Baltic Sea sediment chronology using tephrochronology

2025-06-20

Daniela Müller , Ina Neugebauer , Rebecca Kearney +6 more | Geology

Precise and accurate sediment chronologies are essential for studies of past climate change. In the brackish-marine environment of the Baltic Sea, radiocarbon dating is complicated by varying influx of old … Precise and accurate sediment chronologies are essential for studies of past climate change. In the brackish-marine environment of the Baltic Sea, radiocarbon dating is complicated by varying influx of old carbon and reservoir age changes, challenging the construction of a robust age model. One approach to overcome the problem is well-dated isochronous tie-points like tephra. Here, we present for the first time four cryptotephra horizons in the interval 4500−2000 cal. a BP from sediments of the Western Gotland Basin containing tephra populations from the Hekla-4, Hekla-S, and Hekla-3 eruptions and the Glen Garry and Grákolla tephras from eruptions of Askja and Torfajökull, respectively. In combination with new and published radiocarbon ages, we quantify 14C age offsets for these snapshots in time. In homogeneous sediments, which contain old bulk organic carbon, ages reveal divergences of up to 1200 years. In time intervals not influenced by influx of old carbon, we define a regional marine reservoir age of 250 ± 50 yr. Based on the tephra ages as tie points and applying this reservoir age we calculate a revised age model for the Western Gotland Basin with reduced dating uncertainties that shifts previous chronologies by ∼200 years toward older ages.

Processes and palaeo‐environmental changes in the Arctic from past to present (<scp>PalaeoArc</scp>) – introduction

2025-06-20

Astrid Lyså , Ívar Örn Benediktsson , Nicolaj K. Larsen +2 more | Boreas

Distributions of Protactinium‐231 and Thorium‐230 confirm the critical influence of meridional overturning circulation in the Indian Ocean

2025-06-20

YINGQUN ZHENG , Yiming Luo , Pinghe Cai +2 more | Limnology and Oceanography

Abstract Sedimentary 231 Pa/ 230 Th has been used as a proxy for understanding changes in ocean circulation and productivity over the last glacial–interglacial cycle. Its application relies on the … Abstract Sedimentary 231 Pa/ 230 Th has been used as a proxy for understanding changes in ocean circulation and productivity over the last glacial–interglacial cycle. Its application relies on the influence of meridional overturning circulation (MOC) and particle scavenging on the distribution of 231 Pa and 230 Th in the water column and sediments. While previous studies have addressed the role of MOC on the 230 Th and 231 Pa water profiles and sedimentary 231 Pa/ 230 Th in the Atlantic and Pacific Oceans, including the influence of boundary scavenging in the latter, the impact of these processes in the Indian Ocean remains unresolved. This study employs a two‐dimensional scavenging model with prescribed overturning schemes to simulate the latitudinal distribution of 230 Th and 231 Pa in the water column and sediments of the Indian Ocean. The water column profiles of both nuclides deviate from linearity, reflecting the influence of deep convection, advection, and upwelling controlled by MOC. Additionally, bottom scavenging within the nepheloid layer and boundary scavenging significantly depletes 231 Pa in the Madagascar Basin. The gradual decrease in sediment 231 Pa/ 230 Th below 1500 m in the main basins is primarily linked to MOC, while boundary scavenging contributes to systematically lowering the 231 Pa/ 230 Th. These findings point to the potential of sedimentary 231 Pa/ 230 Th as a proxy for studying the alteration of deep ocean circulation and particle flux in the Indian Ocean.

Glacial erosion and history of Inglefield Land, northwestern Greenland

2025-06-19

Caleb K. Walcott , Allie Balter‐Kennedy , Jason P. Briner +2 more | The cryosphere

Abstract. We used mapping of bedrock lithology, bedrock fractures, and lake density in Inglefield Land, northwestern Greenland, combined with cosmogenic nuclide (10Be and 26Al) measurements in bedrock surfaces, to investigate … Abstract. We used mapping of bedrock lithology, bedrock fractures, and lake density in Inglefield Land, northwestern Greenland, combined with cosmogenic nuclide (10Be and 26Al) measurements in bedrock surfaces, to investigate glacial erosion and the ice sheet history of the northwestern Greenland Ice Sheet. The pattern of eroded versus weathered bedrock surfaces and other glacial erosion indicators reveal temporally and spatially varying erosion under cold- and warm-based ice. All of the bedrock surfaces that we measured in Inglefield Land contain cosmogenic nuclide inheritance with apparent 10Be ages ranging from 24.9 ± 0.5 to 215.8 ± 7.4 ka. The 26Al/10Be ratios require minimum combined surface burial and exposure histories of ∼ 150 to 2000 kyr. Because our sample sites span a relatively small area that experienced a similar ice sheet history, we attribute differences in nuclide concentrations and ratios to varying erosion during the Quaternary. We show that an ice sheet history with ∼ 900 kyr of exposure and ∼ 1800 kyr of ice cover throughout the Quaternary is consistent with the measured nuclide concentrations in most samples when sample-specific subaerial erosion rates are between 0 and 2 × 10−2 mm yr−1 and subglacial erosion rates are between 0 and 2 × 10−3 mm yr−1. These erosion rates help to characterize Arctic landscape evolution in crystalline bedrock terrains in areas away from focused ice flow.

Geyik Dağı Üzerinde Yer Alan Glasiyal Sirkler ile Glasiyo-Karstik Dolinlerin Morfometrik Özellikleri ve Bunların Kuvaterner Kalıcı Kar Sınırı ile İlişkileri / Morphometric Characteristics of Glacial Cirques and Glacio-Karstic Dolines in Mount Geyik and Their Relation to Quaternary Equilibrium Line Altitudes

2025-06-19

Muhammed Zeynel Öztürk , Mesut Şimşek , Mustafa Utlu | Türkiye Jeoloji Bülteni / Geological Bulletin of Turkey

Türkiye’deki dağlık alanların yüksek kesimleri Kuvaterner’in buzul dönemlerinde buzullaşmaya uğradığı için bu alanlarda buzul yer şekillerini yoğun olarak görülmektedir ve bu yer şekilleri, dağlık alanlardaki eski buzullaşma koşullarını anlamamızı sağlar. … Türkiye’deki dağlık alanların yüksek kesimleri Kuvaterner’in buzul dönemlerinde buzullaşmaya uğradığı için bu alanlarda buzul yer şekillerini yoğun olarak görülmektedir ve bu yer şekilleri, dağlık alanlardaki eski buzullaşma koşullarını anlamamızı sağlar. Bu çalışmada, Orta Toroslar önemli karstik platolarından biri olan Geyik Dağı'ndaki sirklerin ve glasiyo-karstik dolinlerin özellikleri incelenmiş ve bu özellikler yardımıyla Kuvaterner buzullaşma dönemlerindeki eski kalıcı kar sınırının (pELA) dağılışı ortaya konmuştur. Haritalama çalışmalarına göre çalışma alanında 142 sirk ve 31 glasiyo-karstik dolin tespit edilmiştir. Bu yer şekillerinin taban yüksekliklerine göre çalışma alanındaki ortalama pELA 2185 m’dir. Ancak bu sınır tek bir seviyede olmayıp; kütlenin uzanımı, yükseklik, denize göre konum ve toplam yağış gibi faktörlere bağlı olarak değişmektedir. pELA yüksek karstik platonun kuzeye bakan kesimlerinde 2400 m’ye kadar çıkarken, batı ve güneybatıya doğru 2000 m ve altına düşmektedir. Elde edilen sonuçlara göre Doğu Karadeniz ve Akdeniz kıyılarındaki dağlık alanların pELA sınırları arasında 630 m’lik bir yükseklik farkı bulunmaktadır. Sirk morfometrisi açısından ise, Doğu Karadeniz’deki sirkler Geyik Dağı'ndaki sirklerden iki kat daha geniş alana sahip olup ve derinlikleri 75 m daha fazladır. Bu sonuçlar ülkemiz kıyılarındaki dağlık alanların topografik ve iklimsel koşullarının pELA seviyeleri ve sirk morfometrileri üzerinde büyük bir etki yaptığını göstermektedir.