Earth and Planetary Sciences › Paleontology

Paleontology and Stratigraphy of Fossils

Works Count: 81216

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This cluster of papers focuses on the use of trace metals, isotopes, and biogeochemical indicators to reconstruct paleoredox conditions and paleoproductivity in ancient oceans. It explores topics such as oceanic anoxic events, atmospheric oxygenation, biogeochemical cycling, and their implications for Phanerozoic climate and mass extinctions.

Keywords

Paleoredox; Paleoproductivity; Trace Metals; Oceanic Anoxic Events; Atmospheric Oxygenation; Biogeochemical Cycling; Isotope Geochemistry; Marine Sediments; Phanerozoic Climate; Mass Extinctions

A Late Devonian Reef Tract on Northeastern Banks Island, N.W.T.

1971-12-01

Ashton F. Embry , J. E. Klovan

ABSTRACT The Upper Devonian Weatherall Formation, outcropping on northeastern Banks Island, N.W.T., contains a 200-ft-thick limestone unit here termed the Mercy Bay Member. The member is Middle to Late Frasnian … ABSTRACT The Upper Devonian Weatherall Formation, outcropping on northeastern Banks Island, N.W.T., contains a 200-ft-thick limestone unit here termed the Mercy Bay Member. The member is Middle to Late Frasnian in age. Gyrfalcon Bluff has been chosen as the type section. Mercy Bay Member outcrops on the extreme northeastern portion of Banks Island, and many excellent exposures permit detailed paleogeographical and paleoecological studies. The member contains numerous organic build-ups and represents a Late Devonian reef tract located in the marine-shelf environment of an exogeosyncline situated between a tectonic highland to the northwest and a stable craton to the southeast. The main facies changes in the Mercy Bay Member occur in an east-west direction. The organic build-ups in the eastern part of the study area are narrow, linear bioherms trending north-south. They are encased in younger terrigenous clastic rocks. To the west the organic build-ups, which are biohermal in the lower part and biostromal in the upper, are more numerous. The lower bioherms trend east-west. Penecontemporaneous interbiohermal strata consist of dark, fine-grained argillaceous limestone. Organic build-ups on the western edge of the outcrop area are bioherms which trend north-south. The lower portion in all organic build-ups consists of corals and tabular stromatoporoids. These are interpreted as biogenetic banks constructed in the quiet and intermediate-energy zones (water depths more than 30 ft). The upper portion is composed of massive stromatoporoids. This facies represents rigid reefs constructed in the high-energy zone (above 30 feet). Successive sea-level rises allowed the reefs to grow upward. Cessation of reef growth was caused by an influx of terrigenous sediment related to the seaward migration of the northern and western shorelines. The outcropping organic build-ups of the Mercy Bay Member are tightly cemented, but frequent bitumen occurrences indicate that they were once oilbearing. Organic build-ups of the Mercy Bay Member probably occur in the subsurface to the west. End_Page 730------------------------

Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid‐Cretaceous

2002-08-23

R. M. Leckie , Timothy J. Bralower , Richard Cashman

Mid‐Cretaceous (Barremian‐Turonian) plankton preserved in deep‐sea marl, organic‐rich shale, and pelagic carbonate hold an important record of how the marine biosphere responded to short‐ and long‐term changes in the ocean‐climate … Mid‐Cretaceous (Barremian‐Turonian) plankton preserved in deep‐sea marl, organic‐rich shale, and pelagic carbonate hold an important record of how the marine biosphere responded to short‐ and long‐term changes in the ocean‐climate system. Oceanic anoxic events (OAEs) were short‐lived episodes of organic carbon burial that are distinguished by their widespread distribution as discrete beds of black shale and/or pronounced carbon isotopic excursions. OAE1a in the early Aptian (∼120.5 Ma) and OAE2 at the Cenomanian/Turonian boundary (∼93.5 Ma) were global in their distribution and associated with heightened marine productivity. OAE1b spans the Aptian/Albian boundary (∼113–109 Ma) and represents a protracted interval of dysoxia with multiple discrete black shales across parts of Tethys (including Mexico), while OAE1d developed across eastern and western Tethys and in other locales during the latest Albian (∼99.5 Ma). Mineralized plankton experienced accelerated rates of speciation and extinction at or near the major Cretaceous OAEs, and strontium isotopic evidence suggests a possible link to times of rapid oceanic plateau formation and/or increased rates of ridge crest volcanism. Elevated levels of trace metals in OAE1a and OAE2 strata suggest that marine productivity may have been facilitated by increased availability of dissolved iron. The association of plankton turnover and carbon isotopic excursions with each of the major OAEs, despite the variable geographic distribution of black shale accumulation, points to widespread changes in the ocean‐climate system. Ocean crust production and hydrothermal activity increased in the late Aptian. Faster spreading rates [and/or increased ridge length] drove a long‐term (Albian–early Turonian) rise in sea level and CO 2 ‐induced global warming. Changes in ocean circulation, water column stratification, and nutrient partitioning lead to a reorganization of plankton community structure and widespread carbonate (chalk) deposition during the Late Cretaceous. We conclude that there were important linkages between submarine volcanism, plankton evolution, and the cycling of carbon through the marine biosphere.

87Sr/86Sr, δ13C and δ18O evolution of Phanerozoic seawater

1999-09-01

Ján Veizer , Davin Ala , Karem Azmy +7 more

A total of 2128 calcitic and phosphatic shells, mainly brachiopods with some conodonts and belemnites, were measured for their δ18O, δ13C and 87Sr/86Sr values. The dataset covers the Cambrian to … A total of 2128 calcitic and phosphatic shells, mainly brachiopods with some conodonts and belemnites, were measured for their δ18O, δ13C and 87Sr/86Sr values. The dataset covers the Cambrian to Cretaceous time interval. Where possible, these samples were collected at high temporal resolution, up to 0.7 Ma (one biozone), from the stratotype sections of all continents but Antarctica and from many sedimentary basins. Paleogeographically, the samples are mostly from paleotropical domains. The scanning electron microscopy (SEM), petrography, cathodoluminescence and trace element results of the studied calcitic shells and the conodont alteration index (CAI) data of the phosphatic shells are consistent with an excellent preservation of the ultrastructure of the analyzed material. These datasets are complemented by extensive literature compilations of Phanerozoic low-Mg calcitic, aragonitic and phosphatic isotope data for analogous skeletons. The oxygen isotope signal exhibits a long-term increase of δ18O from a mean value of about −8‰ (PDB) in the Cambrian to a present mean value of about 0‰ (PDB). Superimposed on the general trend are shorter-term oscillations with their apexes coincident with cold episodes and glaciations. The carbon isotope signal shows a similar climb during the Paleozoic, an inflexion in the Permian, followed by an abrupt drop and subsequent fluctuations around the modern value. The 87Sr/86Sr ratios differ from the earlier published curves in their greater detail and in less dispersion of the data. The means of the observed isotope signals for 87Sr/86Sr, δ18O, δ13C and the less complete δ34S (sulfate) are strongly interrelated at any geologically reasonable (1 to 40 Ma) time resolution. All correlations are valid at the 95% level of confidence, with the most valid at the 99% level. Factor analysis indicates that the 87Sr/86Sr, δ18O, δ13C and δ34S isotope systems are driven by three factors. The first factor links oxygen and strontium isotopic evolution, the second 87Sr/86Sr and δ34S, and the third one the δ13C and δ34S. These three factors explain up to 79% of the total variance. We tentatively identify the first two factors as tectonic, and the third one as a (biologically mediated) redox linkage of the sulfur and carbon cycles. On geological timescales (≥1 Ma), we are therefore dealing with a unified exogenic (litho-, hydro-, atmo-, biosphere) system driven by tectonics via its control of (bio)geochemical cycles.

Geochemistry of oceanic anoxic events

2010-03-01

Hugh C. Jenkyns

Oceanic anoxic events (OAEs) record profound changes in the climatic and paleoceanographic state of the planet and represent major disturbances in the global carbon cycle. OAEs that manifestly caused major … Oceanic anoxic events (OAEs) record profound changes in the climatic and paleoceanographic state of the planet and represent major disturbances in the global carbon cycle. OAEs that manifestly caused major chemical change in the Mesozoic Ocean include those of the early Toarcian (Posidonienschiefer event, T‐OAE, ∼183 Ma), early Aptian (Selli event, OAE 1a, ∼120 Ma), early Albian (Paquier event, OAE 1b, ∼111 Ma), and Cenomanian–Turonian (Bonarelli event, C/T OAE, OAE 2, ∼93 Ma). Currently available data suggest that the major forcing function behind OAEs was an abrupt rise in temperature, induced by rapid influx of CO 2 into the atmosphere from volcanogenic and/or methanogenic sources. Global warming was accompanied by an accelerated hydrological cycle, increased continental weathering, enhanced nutrient discharge to oceans and lakes, intensified upwelling, and an increase in organic productivity. An increase in continental weathering is typically recorded by transient increases in the seawater values of 87 Sr/ 86 Sr and 187 Os/ 188 Os ratios acting against, in the case of the Cenomanian‐Turonian and early Aptian OAEs, a longer‐term trend to less radiogenic values. This latter trend indicates that hydrothermally and volcanically sourced nutrients may also have stimulated local increases in organic productivity. Increased flux of organic matter favored intense oxygen demand in the water column, as well as increased rates of marine and lacustrine carbon burial. Particularly in those restricted oceans and seaways where density stratification was favored by paleogeography and significant fluvial input, conditions could readily evolve from poorly oxygenated to anoxic and ultimately euxinic (i.e., sulfidic), this latter state being geochemically the most significant. The progressive evolution in redox conditions through phases of denitrification/anammox, through to sulfate reduction accompanied by water column precipitation of pyrite framboids, resulted in fractionation of many isotope systems (e.g., N, S, Fe, Mo, and U) and mobilization and incorporation of certain trace elements into carbonates (Mn), sulfides, and organic matter. Sequestration of CO 2 in organic‐rich black shales and by reaction with silicate rocks exposed on continents would ultimately restore climatic equilibrium but at the expense of massive chemical change in the oceans and over time scales of tens to hundreds of thousands of years.

U-Pb Ages from the Neoproterozoic Doushantuo Formation, China

2005-02-25

Daniel J. Condon , Maoyan Zhu , Samuel A. Bowring +3 more

U-Pb zircon dates from volcanic ash beds within the Doushantuo Formation (China) indicate that its deposition occurred between 635 and 551 million years ago. The base records termination of the … U-Pb zircon dates from volcanic ash beds within the Doushantuo Formation (China) indicate that its deposition occurred between 635 and 551 million years ago. The base records termination of the global-scale Marinoan glaciation and is coeval with similar dated rocks from Namibia, indicating synchronous deglaciation. Carbon isotopic and sequence-stratigraphic data imply that the spectacular animal fossils of the Doushantuo Formation are for the most part younger than 580 million years old. The uppermost Doushantuo Formation contains a pronounced negative carbonate carbon isotopic excursion, which we interpret as a global event at circa 551 million years ago.

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The rise of oxygen in Earth’s early ocean and atmosphere

2014-02-01

Timothy W. Lyons , Christopher T. Reinhard , Noah J. Planavsky

The geochemistry of the stable carbon isotopes

1953-02-01

Harmon Craig

Late-Neoproterozoic Deep-Ocean Oxygenation and the Rise of Animal Life

2006-12-08

Donald E. Canfield , Simon W. Poulton , Guy M. Narbonne

Because animals require oxygen, an increase in late-Neoproterozoic oxygen concentrations has been suggested as a stimulus for their evolution. The iron content of deep-sea sediments shows that the deep ocean … Because animals require oxygen, an increase in late-Neoproterozoic oxygen concentrations has been suggested as a stimulus for their evolution. The iron content of deep-sea sediments shows that the deep ocean was anoxic and ferruginous before and during the Gaskiers glaciation 580 million years ago and that it became oxic afterward. The first known members of the Ediacara biota arose shortly after the Gaskiers glaciation, suggesting a causal link between their evolution and this oxygenation event. A prolonged stable oxic environment may have permitted the emergence of bilateral motile animals some 25 million years later.

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Oceanic Anoxia and the End Permian Mass Extinction

1996-05-24

Paul B. Wignall , Richard J. Twitchett

Data on rocks from Spitsbergen and the equatorial sections of Italy and Slovenia indicate that the world's oceans became anoxic at both low and high paleolatitudes in the Late Permian. … Data on rocks from Spitsbergen and the equatorial sections of Italy and Slovenia indicate that the world's oceans became anoxic at both low and high paleolatitudes in the Late Permian. Such conditions may have been responsible for the mass extinction at this time. This event affected a wide range of shelf depths and extended into shallow water well above the storm wave base.

A Chronology of Paleozoic Sea-Level Changes

2008-10-02

Bilal U. Haq , Stephen R. Schutter

Sea levels have been determined for most of the Paleozoic Era (542 to 251 million years ago), but an integrated history of sea levels has remained unrealized. We reconstructed a … Sea levels have been determined for most of the Paleozoic Era (542 to 251 million years ago), but an integrated history of sea levels has remained unrealized. We reconstructed a history of sea-level fluctuations for the entire Paleozoic by using stratigraphic sections from pericratonic and cratonic basins. Evaluation of the timing and amplitude of individual sea-level events reveals that the magnitude of change is the most problematic to estimate accurately. The long-term sea level shows a gradual rise through the Cambrian, reaching a zenith in the Late Ordovician, then a short-lived but prominent withdrawal in response to Hirnantian glaciation. Subsequent but decreasingly substantial eustatic highs occurred in the mid-Silurian, near the Middle/Late Devonian boundary, and in the latest Carboniferous. Eustatic lows are recorded in the early Devonian, near the Mississippian/Pennsylvanian boundary, and in the Late Permian. One hundred and seventy-two eustatic events are documented for the Paleozoic, varying in magnitude from a few tens of meters to approximately 125 meters.

Questioning the evidence for Earth's oldest fossils

2002-03-01

Martin D. Brasier , Owen R. Green , A. P. Jephcoat +5 more

The size distribution of framboidal pyrite in modern sediments: An indicator of redox conditions

1996-10-01

Richard T. Wilkin , H. L. Barnes , Susan L. Brantley

Sedimentary Environments and Facies

1986-10-01

David J. Bottjer , H. G. Reading

Facies alluvial sediments lakes deserts deltas siliciclastic shorelines arid shorelines and evaporites shallow siliciclastic seas shallow-marine carbonate environments pelagic environments deep clastic seas glacial environments sedimentation and tectonics problems and … Facies alluvial sediments lakes deserts deltas siliciclastic shorelines arid shorelines and evaporites shallow siliciclastic seas shallow-marine carbonate environments pelagic environments deep clastic seas glacial environments sedimentation and tectonics problems and perspectives.

Evidence for life on Earth before 3,800 million years ago

1996-11-07

S. J. Mojzsis , Gustaf Arrhenius , K. D. McKeegan +3 more

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An Overview of Biomineralization Processes and the Problem of the Vital Effect

2003-01-01

Steve Weiner , Patricia M. Dove

Research Article| January 03, 2003 An Overview of Biomineralization Processes and the Problem of the Vital Effect Steve Weiner; Steve Weiner Department of Structural Biology, Weizmann Institute of Science, 76100 … Research Article| January 03, 2003 An Overview of Biomineralization Processes and the Problem of the Vital Effect Steve Weiner; Steve Weiner Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot Israel Search for other works by this author on: GSW Google Scholar Patricia M. Dove Patricia M. Dove Department of GeoSciences, Virginia Tech, Blacksburg, Virginia 24061 U.S.A. Search for other works by this author on: GSW Google Scholar Reviews in Mineralogy and Geochemistry (2003) 54 (1): 1–29. https://doi.org/10.2113/0540001 Article history first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Steve Weiner, Patricia M. Dove; An Overview of Biomineralization Processes and the Problem of the Vital Effect. Reviews in Mineralogy and Geochemistry 2003;; 54 (1): 1–29. doi: https://doi.org/10.2113/0540001 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyReviews in Mineralogy and Geochemistry Search Advanced Search "Biomineralization links soft organic tissues, which are compositionally akin to the atmosphere and oceans, with the hard materials of the solid Earth. It provides organisms with skeletons and shells while they are alive, and when they die these are deposited as sediment in environments from river plains to the deep ocean floor. It is also these hard, resistant products of life which are mainly responsible for the Earth's fossil record. Consequently, biomineralization involves biologists, chemists, and geologists in interdisciplinary studies at one of the interfaces between Earth and life."(Leadbeater and Riding 1986) Biomineralization refers to the processes... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Periodicity of extinctions in the geologic past.

1984-02-01

David M. Raup , J. John Sepkoski

The temporal distribution of the major extinctions over the past 250 million years has been investigated statistically using various forms of time series analysis. The analyzed record is based on … The temporal distribution of the major extinctions over the past 250 million years has been investigated statistically using various forms of time series analysis. The analyzed record is based on variation in extinction intensity for fossil families of marine vertebrates, invertebrates, and protozoans and contains 12 extinction events. The 12 events show a statistically significant periodicity (P less than 0.01) with a mean interval between events of 26 million years. Two of the events coincide with extinctions that have been previously linked to meteorite impacts (terminal Cretaceous and Late Eocene). Although the causes of the periodicity are unknown, it is possible that they are related to extraterrestrial forces (solar, solar system, or galactic).

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THE EARLY HISTORY OF ATMOSPHERIC OXYGEN: Homage to Robert M. Garrels

2005-02-11

Donald E. Canfield

▪ Abstract This paper reviews the Precambrian history of atmospheric oxygen, beginning with a brief discussion of the possible nature and magnitude of life before the evolution of oxygenic photosynthesis. … ▪ Abstract This paper reviews the Precambrian history of atmospheric oxygen, beginning with a brief discussion of the possible nature and magnitude of life before the evolution of oxygenic photosynthesis. This is followed by a summary of the various lines of evidence constraining oxygen levels through time, resulting in a suggested history of atmospheric oxygen concentrations. Also reviewed are the various processes regulating oxygen concentrations, and several models of Precambrian oxygen evolution are presented. A sparse geologic record, combined with uncertainties as to its interpretation, yields only a fragmentary and imprecise reading of atmospheric oxygen evolution. Nevertheless, oxygen levels have increased through time, but not monotonically, with major and fascinating swings to both lower and higher levels.

Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-isotope studies

1996-07-01

Donald E. Canfield , Andreas Teske

Isotopic evidence for source of diagenetic carbonates formed during burial of organic-rich sediments

1977-09-01

Hilary Irwin , C. D. Curtis , Max Coleman

Microbialites: Organosedimentary Deposits of Benthic Microbial Communities

1987-01-01

Robert V. Burne , Linda S. Moore

Microbialites are organosedimentary deposits formed from interaction between benthic microbial communities (BMCs) and detrital or chemical sediments. Processes involved in the formation of calcareous microbialites include trapping and binding of … Microbialites are organosedimentary deposits formed from interaction between benthic microbial communities (BMCs) and detrital or chemical sediments. Processes involved in the formation of calcareous microbialites include trapping and binding of detrital sediment (forming microbial boundstones), inorganic calcification (forming microbial tufa), and biologically influenced calcification (forming microbial framestones). Microbialites contrast with other biological sediments in that they are generally not composed of skeletal remains. -from Authors

Carbon Dioxide Exchange Between Atmosphere and Ocean and the Question of an Increase of Atmospheric CO2 during the Past Decades

1957-01-01

Roger Revelle , Hans E. Sueß

From a comparison of C14/C12 and C13/C12 ratios in wood and in marine material and from a slight decrease of the C14 concentration in terrestrial plants over the past 50 … From a comparison of C14/C12 and C13/C12 ratios in wood and in marine material and from a slight decrease of the C14 concentration in terrestrial plants over the past 50 years it can be concluded that the average lifetime of a CO2 molecule in the atmosphere before it is dissolved into the sea is of the order of 10 years. This means that most of the CO2 released by artificial fuel combustion since the beginning of the industrial revolution must have been absorbed by the oceans. The increase of atmospheric CO2 from this cause is at present small but may become significant during future decades if industrial fuel combustion continues to rise exponentially. Present data on the total amount of CO2 in the atmosphere, on the rates and mechanisms of exchange, and on possible fluctuations in terrestrial and marine organic carbon, are inadequate for accurate measurement of future changes in atmospheric CO2. An opportunity exists during the International Geophysical Year to obtain much of the necessary information.

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Lethally Hot Temperatures During the Early Triassic Greenhouse

2012-10-19

Yadong Sun , Michael M. Joachimski , Paul B. Wignall +5 more

Too-Hot Times Climate warming has been invoked as a factor contributing to widespread extinction events, acting as a trigger or amplifier for more proximal causes, such as marine anoxia. Sun … Too-Hot Times Climate warming has been invoked as a factor contributing to widespread extinction events, acting as a trigger or amplifier for more proximal causes, such as marine anoxia. Sun et al. (p. 366 ; see the Perspective by Bottjer ) present evidence that exceptionally high temperatures themselves may have caused some extinctions during the end-Permian. A rapid temperature rise coincided with a general absence of ichthyofauna in equatorial regions, as well as an absence of many species of marine mammals and calcareous algae, consistent with thermal influences on the marine low latitudes. Sea surface temperatures approached 40°C, which suggests that land temperatures likely fluctuated to even higher values that suppressed terrestrial equatorial plant and animal abundance during most of the Early Triassic.

Large igneous provinces and mass extinctions

2001-03-01

Paul B. Wignall

Environmental analysis of paleoceanographic systems based on molybdenum–uranium covariation

2009-09-13

Thomas J. Algeo , Nicolas Tribovillard

Dolomite: occurrence, evolution and economically important associations

2000-11-01

John K. Warren

Dating the rise of atmospheric oxygen

2004-01-01

Andrey Bekker , Heinrich Holland , Pei‐Ling Wang +5 more

Oxidation of the Ediacaran Ocean

2006-12-06

David A. Fike , J. P. Grotzinger , Lisa M. Pratt +1 more

Processes of carbonate precipitation in modern microbial mats

2008-11-18

Christophe Dupraz , R. Pamela Reid , Olivier Braissant +3 more

A Neoproterozoic Snowball Earth

1998-08-28

Paul F. Hoffman , Alan J. Kaufman , Galen P. Halverson +1 more

Negative carbon isotope anomalies in carbonate rocks bracketing Neoproterozoic glacial deposits in Namibia, combined with estimates of thermal subsidence history, suggest that biological productivity in the surface ocean collapsed for … Negative carbon isotope anomalies in carbonate rocks bracketing Neoproterozoic glacial deposits in Namibia, combined with estimates of thermal subsidence history, suggest that biological productivity in the surface ocean collapsed for millions of years. This collapse can be explained by a global glaciation (that is, a snowball Earth), which ended abruptly when subaerial volcanic outgassing raised atmospheric carbon dioxide to about 350 times the modern level. The rapid termination would have resulted in a warming of the snowball Earth to extreme greenhouse conditions. The transfer of atmospheric carbon dioxide to the ocean would result in the rapid precipitation of calcium carbonate in warm surface waters, producing the cap carbonate rocks observed globally.

Cretaceous oceanic anoxic events: causes and consequences

2007-10-01

S. O. Schlanger , Hugh C. Jenkyns

Organic carbon-rich sediments are globally developed in pelagic sedimentary sequences of Aptian-Albian and Cenomanian-Turonian age. They formed in a variety of paleo-bathymetric settings including oceanic plateaus and basins, continental margins … Organic carbon-rich sediments are globally developed in pelagic sedimentary sequences of Aptian-Albian and Cenomanian-Turonian age. They formed in a variety of paleo-bathymetric settings including oceanic plateaus and basins, continental margins and shelf seas. The widespread nature of these deposits suggests that they were not strictly controlled by local basin geometry but were a product of ″Oceanic Anoxic Events″ . Interpretation of these events as the result of the interplay of two major geologic and climatic factors is given. The Late Cretaceous transgression which increased the area and volume of shallow epicontinental and marginal seas and was accompanied by an increase in the production of organic carbon; and the existence of an equable global climate which reduced the supply of cold oxygenated bottom water to the world ocean. This combination of climatic and hypsographic conditions favoured the formation of an expanded oxygen-minimum layer and where this intersected the sediment-water interface, organic carbon-rich deposits could be formed, these being records of ″Oceanic Anoxic Events″ .

The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals

2011-11-24

Douglas H. Erwin , Marc Laflamme , Sarah M. Tweedt +3 more

Diverse bilaterian clades emerged apparently within a few million years during the early Cambrian, and various environmental, developmental, and ecological causes have been proposed to explain this abrupt appearance. A … Diverse bilaterian clades emerged apparently within a few million years during the early Cambrian, and various environmental, developmental, and ecological causes have been proposed to explain this abrupt appearance. A compilation of the patterns of fossil and molecular diversification, comparative developmental data, and information on ecological feeding strategies indicate that the major animal clades diverged many tens of millions of years before their first appearance in the fossil record, demonstrating a macroevolutionary lag between the establishment of their developmental toolkits during the Cryogenian [(850 to 635 million years ago (Ma)], and the later ecological success of metazoans during the Ediacaran (635 to 541 Ma) and Cambrian (541 to 488 Ma) periods. We argue that this diversification involved new forms of developmental regulation, as well as innovations in networks of ecological interaction within the context of permissive environmental circumstances.

The oxygenation of the atmosphere and oceans

2006-05-19

Heinrich Holland

The last 3.85 Gyr of Earth history have been divided into five stages. During stage 1 (3.85–2.45 Gyr ago (Ga)) the atmosphere was largely or entirely anoxic, as were the … The last 3.85 Gyr of Earth history have been divided into five stages. During stage 1 (3.85–2.45 Gyr ago (Ga)) the atmosphere was largely or entirely anoxic, as were the oceans, with the possible exception of oxygen oases in the shallow oceans. During stage 2 (2.45–1.85 Ga) atmospheric oxygen levels rose to values estimated to have been between 0.02 and 0.04 atm. The shallow oceans became mildly oxygenated, while the deep oceans continued anoxic. Stage 3 (1.85–0.85 Ga) was apparently rather ‘boring’. Atmospheric oxygen levels did not change significantly. Most of the surface oceans were mildly oxygenated, as were the deep oceans. Stage 4 (0.85–0.54 Ga) saw a rise in atmospheric oxygen to values not much less than 0.2 atm. The shallow oceans followed suit, but the deep oceans were anoxic, at least during the intense Neoproterozoic ice ages. Atmospheric oxygen levels during stage 5 (0.54 Ga–present) probably rose to a maximum value of ca 0.3 atm during the Carboniferous before returning to its present value. The shallow oceans were oxygenated, while the oxygenation of the deep oceans fluctuated considerably, perhaps on rather geologically short time-scales.

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The Petrology of the Sedimentary Rocks

1938-08-01

Robert L. Folk

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The Evolution of Modern Eukaryotic Phytoplankton

2004-07-15

Paul G. Falkowski , Miriam Katz , Andrew H. Knoll +4 more

The community structure and ecological function of contemporary marine ecosystems are critically dependent on eukaryotic phytoplankton. Although numerically inferior to cyanobacteria, these organisms are responsible for the majority of the … The community structure and ecological function of contemporary marine ecosystems are critically dependent on eukaryotic phytoplankton. Although numerically inferior to cyanobacteria, these organisms are responsible for the majority of the flux of organic matter to higher trophic levels and the ocean interior. Photosynthetic eukaryotes evolved more than 1.5 billion years ago in the Proterozoic oceans. However, it was not until the Mesozoic Era (251 to 65 million years ago) that the three principal phytoplankton clades that would come to dominate the modern seas rose to ecological prominence. In contrast to their pioneering predecessors, the dinoflagellates, coccolithophores, and diatoms all contain plastids derived from an ancestral red alga by secondary symbiosis. Here we examine the geological, geochemical, and biological processes that contributed to the rise of these three, distantly related, phytoplankton groups.

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Chemical Diagenesis of a Multicomponent Carbonate System--1: Trace Elements

1980-01-01

Uwe Brand , Ján Veizer

ABSTRACT Theoretical considerations (i.e., partition coefficients, water/rock ratio, chemistry of interstitial meteoric water) of elemental behaviour during diagenetic stabilization with meteoric waters suggests that it leads to a decrease in … ABSTRACT Theoretical considerations (i.e., partition coefficients, water/rock ratio, chemistry of interstitial meteoric water) of elemental behaviour during diagenetic stabilization with meteoric waters suggests that it leads to a decrease in strontium, sodium, and possibly magnesium and an increase in manganese, iron, and zinc in progressively altered carbonates. Such elemental behaviour is exhibited by the different carbonate components of the Mississippian Burlington Limestone of Iowa and Missouri and the Silurian Read Bay Formation of Arctic Canada. In the Burlington Limestone the rock matrix (e.g., biosparite), the enclosed crinoids, and to some degree the rugose corals are chemically similar. The crinoid ossicles have average strontium content of 160 ppm, rugose corals 180 ppm, and the enclosing biosparite 120 ppm. In contrast, in the Read Bay Formation each of the above mentioned components has a specific chemistry, with 210 ppm strontium for crinoids, 780 ppm for rugose corals, and 360 ppm for their enclosing micrite matrix. These chemical trends are accompanied by textural changes of the host carbonate sediments. In the Burlington Lime tone this involves the presence of depositional sparite, whereas in the Read Bay Formation this increase in textural maturity involves the transition from micrite to microspar to minor pseudospar and sparite. The combination of these textural trends with the elemental patterns shows that the degree with which a particular carbonate component approaches either the open system or the partly closed system equilibrium is dictated by its respective mineralogical stability and the water/rock ratio. While the results show that the carbonate assemblage may act as a completely open diagenetic system (e.g., Burlington Limestone), available data for the majority of studied sequences (e.g., Read Bay Formation) suggest that diagenetic equilibration ceases while some original depositional differences in chemical composition are still preserved. This implies that diagenetic stabilization proceeds through partly closed reaction zones on solid-liquid interfaces. Transfer of the chemical and textural inform tion from the dissolving phase (original sedimentary carbonate particle) to the precipitating phase (diagenetic carbonate component) proceeds via a Messenger Film water in the reaction zone, which is in disequilibrium with the meteoric bulk aquifer water. Thus the chemical composition of carbonate components of ancient limestones may serve as a potential tool for evaluating the degree of diagenesis and for deducing the original mineralogy of the different stabilized carbonate phases. Application of this trace element model suggests that Paleozoic crinoids were composed originally of metastable high-magnesium calcite, rugose corals were composed originally of stable low-magnesium calcite or high-magnesium calcite with low Mg2+ content, and micrite was origially aragonite lime mud.

Microbial carbonates: the geological record of calcified bacterial–algal mats and biofilms

2000-02-01

Robert Riding

Summary Deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the Archaean. Geologically best known in seas and lakes, microbial carbonates are also important … Summary Deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the Archaean. Geologically best known in seas and lakes, microbial carbonates are also important at the present day in fluviatile, spring, cave and soil environments. The principal organisms involved are bacteria, particularly cyanobacteria, small algae and fungi, that participate in the growth of microbial biofilms and mats. Grain‐trapping is locally important, but the key process is precipitation, producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation. Various metabolic processes, such as photosynthetic uptake of CO 2 and/or HCO 3 – by cyanobacteria, and ammonification, denitrification and sulphate reduction by other bacteria, can increase alkalinity and stimulate carbonate precipitation. Extracellular polymeric substances, widely produced by microbes for attachment and protection, are important in providing nucleation sites and facilitating sediment trapping. Microbial carbonate microfabrics are heterogeneous. They commonly incorporate trapped particles and in situ algae and invertebrates, and crystals form around bacterial cells, but the main component is dense, clotted or peloidal micrite resulting from calcification of bacterial cells, sheaths and biofilm, and from phytoplankton‐stimulated whiting nucleation. Interpretation of these texturally convergent and often inscrutable fabrics is a challenge. Conspicuous accumulations are large domes and columns with laminated (stromatolite), clotted (thrombolite) and other macrofabrics, which may be either agglutinated or mainly composed of calcified or spar‐encrusted microbes. Stromatolite lamination appears to be primary, but clotted thrombolite fabrics can be primary or secondary. Microbial precipitation also contributes to hot‐spring travertine, cold‐spring mound, calcrete, cave crust and coated grain deposits, as well as influencing carbonate cementation, recrystallization and replacement. Microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water, and thus relies uniquely on a combination of biotic and abiotic factors. This overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas, and in the past by temporal variation in abundance of marine microbial carbonates. Patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry. Stromatolites appeared at ∼3450 Ma and were generally diverse and abundant from 2800 to 1000 Ma. Inception of a Proterozoic decline variously identified at 2000, 1000 and 675 Ma, has been attributed to eukaryote competition and/or reduced lithification. Thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the Palaeozoic, and reappeared in the Late Devonian. Microbial carbonates retained importance through much of the Mesozoic, became scarcer in marine environments in the Cenozoic, but locally re‐emerged as large agglutinated domes, possibly reflecting increased algal involvement, and thick micritic reef crusts in the late Neogene. Famous modern examples at Shark Bay and Lee Stocking Island are composite coarse agglutinated domes and columns with complex bacterial–algal mats occurring in environments that are both stressed and current‐swept: products of mat evolution, ecological refugia, sites of enhanced early lithification or all three?

GEOCARBSULF: A combined model for Phanerozoic atmospheric O2 and CO2

2006-05-26

Robert A. Berner

Microfossils of the Early Archean Apex Chert: New Evidence of the Antiquity of Life

1993-04-30

J. William Schopf

Eleven taxa (including eight heretofore undescribed species) of cellularly preserved filamentous microbes, among the oldest fossils known, have been discovered in a bedded chert unit of the Early Archean Apex … Eleven taxa (including eight heretofore undescribed species) of cellularly preserved filamentous microbes, among the oldest fossils known, have been discovered in a bedded chert unit of the Early Archean Apex Basalt of northwestern Western Australia. This prokaryotic assemblage establishes that trichomic cyanobacterium-like microorganisms were extant and morphologically diverse at least as early as ∼3465 million years ago and suggests that oxygen-producing photoautotrophy may have already evolved by this early stage in biotic history.

Carbonate Depositional Environments

1983-01-01

Peter A. Scholle , Don G. Bebout , Clyde H. Moore

For more than 100 years geologists have been ex amining and describing modern sediments with an eye toward using characteristic features to aid in the interpretation of depositional settings of … For more than 100 years geologists have been ex amining and describing modern sediments with an eye toward using characteristic features to aid in the interpretation of depositional settings of ancient strata. This field of interest developed particularly during the 1950s and 1960s with the creation of detailed models for modern carbonate deposition in Florida, the Bahamas, Cuba, the Persian Gulf, Belize, Pacific atolls, the Great Barrier Reef and other areas. An understanding of the depositional environments of these modern models, coupled with increased understanding of diagenetic effects, has led to vastly improved interpretations of ancient limestones. Such models also improved the “predictability” of many carbonate reservoir rocks.In spite of the great strides made in our knowledge about carbonate depositional environments, their characteristic features have never been synthesized in a single work. Although excellent textbooks exist which describe some aspects of the interpretation of both ancient strata and modern sediments, systematic treatment of the entire subject is available only in the primary literature.This book is an attempt to bring together this widely disseminated literature. The volume is specifically designed for use by the non—specialist-the petroleum geologist or field geologist—who needs to use carbonate depositional environments in facies reconstructions and environmental interpretations. Yet it is hoped that the book will also serve as a valuable reference for the specialist or advanced graduate student.Toward that purpose, the book is extensively illustrated with color diagrams and photographs of sedimentary structures and facies assemblages. The text focuses on the recognition of depositional environments rather than on the hydrodynamic mechanisms of sediment movement.

ARC ASSEMBLY AND CONTINENTAL COLLISION IN THE NEOPROTEROZOIC EAST AFRICAN OROGEN: Implications for the Consolidation of Gondwanaland

1994-05-01

Robert J. Stern

Some of the most important, rapid, and enigmatic changes in our Earth’s environment and biota occurred during the Neoproterozoic Era (1000540 million years ago; Ma). Paramount among these changes are … Some of the most important, rapid, and enigmatic changes in our Earth’s environment and biota occurred during the Neoproterozoic Era (1000540 million years ago; Ma). Paramount among these changes are the rapid evolution of eukaryotes and appearance of metazoa (Knoll 1992, Conway Morris 1993), major episodes of continental glaciation that may have extended to low latitudes (Hambrey & Harland 1985), marked increases in the oxygen concentration of the atmosphere and hydrosphere (Derry et al 1992), the reappearance of sedimentary banded iron formations (BIF; James 1983), and striking temporal variations in the isotopic composition of C and Sr (Asmerom et al 1991, Derry et al 1992). Understanding the causes of and relationships between these changes is a challenging focus of interdisciplinary research, and there are compelling indications that the most important causes were tectonic (Des Marais et al 1992, Veevers 1990). For example, development of ocean basins may have been accompanied by the development of seafloor hydrothermal systems, which lowered the 87Sr/S6Sr of seawater, led to the development of BIF, and formed anoxic basins where organic carbon could be buried, thus leading to an increase in O~. Continental collision and formation of a supercontinent may have led to continental glaciation and an increase in the 87Sr/86Sr of seawater,

Ferruginous Conditions: A Dominant Feature of the Ocean through Earth's History

2011-04-01

Simon W. Poulton , Donald E. Canfield

Research Article| April 01, 2011 Ferruginous Conditions: A Dominant Feature of the Ocean through Earth's History Simon W. Poulton; Simon W. Poulton 1School of Civil Engineering and Geosciences, Newcastle University … Research Article| April 01, 2011 Ferruginous Conditions: A Dominant Feature of the Ocean through Earth's History Simon W. Poulton; Simon W. Poulton 1School of Civil Engineering and Geosciences, Newcastle University Drummond Building, Newcastle upon Tyne NE1 7RU, UK E-mail: [email protected] Search for other works by this author on: GSW Google Scholar Donald E. Canfield Donald E. Canfield 2Nordic Centre for Earth Evolution and Institute of Biology University of Southern Denmark, 5230 Odense M, Denmark E-mail: [email protected] Search for other works by this author on: GSW Google Scholar Elements (2011) 7 (2): 107–112. https://doi.org/10.2113/gselements.7.2.107 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Simon W. Poulton, Donald E. Canfield; Ferruginous Conditions: A Dominant Feature of the Ocean through Earth's History. Elements 2011;; 7 (2): 107–112. doi: https://doi.org/10.2113/gselements.7.2.107 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyElements Search Advanced Search Abstract The reconstruction of oceanic paleoredox conditions on Earth is essential for investigating links between biospheric oxygenation and major periods of biological innovation and extinction, and for unravelling feedback mechanisms associated with paleoenvironmental change. The occurrence of anoxic, iron-rich (ferruginous) oceanic conditions often goes unrecognized, but refined techniques are currently providing evidence to suggest that ferruginous deep-ocean conditions were likely dominant throughout much of Earth's history. The prevalence of this redox state suggests that a detailed appraisal of the influence of ferruginous conditions on the evolution of biogeochemical cycles, climate, and the biosphere is increasingly required. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Classification of Carbonate Rocks—A Symposium

1962-01-01

William E. Ham

Limestones and dolomites form the economically important and exceedingly complex family of carbonate rocks. They are set distinctly apart from related rock families by their intrabasinal and highly local origin, … Limestones and dolomites form the economically important and exceedingly complex family of carbonate rocks. They are set distinctly apart from related rock families by their intrabasinal and highly local origin, their genetic dependence upon organic activity, and their extreme susceptibility to post- depositional modification.The successful classification of carbonate rocks requires detailed knowledge of their multiple com-ponents and genetic processes. Such knowledge has been greatly increased during a period of accelerated investigations since 1940, with the result that the modern classifications are marked improvements over their predecessors.Most of the newer classifications utilize a practical blending of descriptive and genetic parameters. The parameters most commonly used are depositional fabric, particularly the relative abundance of coarser carbonate particles (grains) as compared with the finer grained particles (matrix or micrite); the size and genetic types of the grains or of in-place biotic constituents; the mineralogy; and the nature and degree of post-depositional modification. Secondary parameters include porosity, cementation, the degree of abrasion or rounding of the grains, admixtures of noncarbonate material, and a host of others.The symposium classifications of carbonate rocks and two allied articles of this volume are briefly reviewed and compared. Despite the differences in approach, purpose, and experience among the various authors, the resulting classifications show strong similarities and therefore indicate that a basis of mutual

Microfacies of Carbonate Rocks

2009-10-07

Erik Flügel

A factor analytic description of the Phanerozoic marine fossil record

1981-01-01

J. John Sepkoski

Data on numbers of marine families within 91 metazoan classes known from the Phanerozoic fossil record are analyzed. The distribution of the 2800 fossil families among the classes is very … Data on numbers of marine families within 91 metazoan classes known from the Phanerozoic fossil record are analyzed. The distribution of the 2800 fossil families among the classes is very uneven, with most belonging to a small minority of classes. Similarly, the stratigraphic distribution of the classes is very uneven, with most first appearing early in the Paleozoic and with many of the smaller classes becoming extinct before the end of that era. However, despite this unevenness, a Q -mode factor analysis indicates that the structure of these data is rather simple. Only three factors are needed to account for more than 90% of the data. These factors are interpreted as reflecting the three great “evolutionary faunas” of the Phanerozoic marine record: a trilobite-dominated Cambrian fauna, a brachiopod-dominated later Paleozoic fauna, and a mollusc-dominated Mesozoic-Cenozoic, or “modern,” fauna. Lesser factors relate to slow taxonomic turnover within the major faunas through time and to unique aspects of particular taxa and times. Each of the three major faunas seems to have its own characteristic diversity so that its expansion or contraction appears as being intimately associated with a particular phase in the history of total marine diversity. The Cambrian fauna expands rapidly during the Early Cambrian radiations and maintains dominance during the Middle to Late Cambrian “equilibrium.” The Paleozoic fauna then ascends to dominance during the Ordovician radiations, which increase diversity dramatically; this new fauna then maintains dominance throughout the long interval of apparent equilibrium that lasts until the end of the Paleozoic Era. The modern fauna, which slowly increases in importance during the Paleozoic Era, quickly rises to dominance with the Late Permian extinctions and maintains that status during the general rise in diversity to the apparent maximum in the Neogene. The increase in diversity associated with the expansion of each new fauna appears to coincide with an approximately exponential decline of the previously dominant fauna, suggesting possible displacement of each evolutionary fauna by its successor.

Oxygen and carbon isotope fractionation in biogenic aragonite: Temperature effects

1986-10-01

Ethan L. Grossman

Mass Extinctions and Their Aftermath

1997-09-11

A. Hallam , Paul B. Wignall

Abstract Why do mass extinctions occur? The demise of the dinosaurs has been discussed exhaustively, but has never been out into the context of other extinction events. This is the … Abstract Why do mass extinctions occur? The demise of the dinosaurs has been discussed exhaustively, but has never been out into the context of other extinction events. This is the first systematic review of the mass extinctions of all organisms, plant and animal, terrestrial and marine, that have occurred in the history of life. This includes the major crisis 250 million years ago which nearly wiped out all life on Earth. By examining current paleontological, geological, and sedimentological evidence of environmental changes, the cases for explanations based on climate change, marine regressions, asteroid or comet impact, anoxia, and volcanic eruptions are all critically evaluated.

PYRITIZED ROD-SHAPED MICROBES ASSOCIATED WITH A SILICIFIED BRACHIOPOD, PERMIAN, WEST TEXAS

2025-06-24

Leslie A. Melim , Thomas A. Hegna , Brian J. Bellott +2 more | Palaios

Abstract In sedimentary rocks, pyrite framboids are subspherical aggregates of microcrystals that form during decay of organic matter by sulfate reducing organisms (SRO). We report on pyrite found on a … Abstract In sedimentary rocks, pyrite framboids are subspherical aggregates of microcrystals that form during decay of organic matter by sulfate reducing organisms (SRO). We report on pyrite found on a Permian silicified articulate brachiopod shell and address the implications for the pyritization and silicification processes. Four pyrite forms occur, in order of abundance: spherical to subspherical aggregates of microcrystals (framboids), rod-shaped aggregates of microcrystals (pyrite rods), euhedral crystals, and loose microcrystals. It is the pyrite rods that are of most interest here. Pyrite framboids and rods are found scattered in the silica that replaces the shell and in large groups in the surrounding silicified matrix. The microcrystals in pyrite rods have the same morphology and size distribution as those in framboids. The diameter of pyrite rods is slightly less than framboids, but the length is significantly greater. We interpret the pyrite rods as forming just like framboids by burst nucleation of pyrite microcrystals, but within a rod-shaped microbial cell, thus permineralizing that cell. Interestingly, the volume of rods and framboids are similar, suggesting that only cells of the right size and shape were recognizably permineralized. This is the first example of framboid-like pyrite permineralizing isolated microbial cells rather than multicellular microbial filaments. The abundance of pyrite framboids and rods embedded in silica strongly confirms the connection between microbial decay, here specifically including SRO, in a microbial ecosystem, and the silicification process.

Carbonate microfacies and transgressive‐regressive sequences of Oxfordian shallow‐water limestones (Korallenoolith, Lower Saxony Basin)

2025-06-24

Deyan Zhang , François‐Nicolas Krencker , Stefan Huck +1 more | The Depositional Record

Abstract This study represents a detailed analysis of a stratigraphic section of Oxfordian (Late Jurassic) age with the aim to reconstruct the facies pattern and sequence‐stratigraphic evolution, followed by a … Abstract This study represents a detailed analysis of a stratigraphic section of Oxfordian (Late Jurassic) age with the aim to reconstruct the facies pattern and sequence‐stratigraphic evolution, followed by a discussion of the dominant controls on shallow marine carbonate platform sedimentation in the Lower Saxony Basin (LSB). During the Oxfordian, the LSB was covered by a shallow epicontinental sea, in which a thick succession of marine limestones and marls was deposited. The stratiform Oxfordian carbonate bodies hold significant economic potential due to their ability to form hydrocarbon reservoirs or targets for future geothermal exploration. The scarcity of open‐marine biostratigraphic marker fossils and the presence of numerous sedimentary gaps pose significant challenges for establishing reliable correlations with Oxfordian deposits globally. This study focuses on the Oxfordian Korallenoolith Formation, which is well exposed in the Bisperode section located ~40 km SW of Hannover. The ~126 m thick section was described bed‐by‐bed during fieldwork and complemented by 73 petrographic thin sections that were analysed for carbonate microfacies. Based on differences in grain and mud composition and primary sedimentary fabrics, an integrated log of the Bisperode quarry was constructed. Seven facies types (FTs) and 13 microfacies types (MFs) are characterised upon which a reef‐bearing carbonate ramp model was built. Following the magnitude of the transgressive/regressive trends concept, three low‐order sequences are recognised, which are composed of eight higher order sequences. The low‐order sequences correlate well to the established sequence‐stratigraphic model and the higher order sequences point to a possible control of their stacking pattern by Milankovitch long eccentricity cycles. This study is important because it helps to better understand the link between the stacking pattern of Oxfordian strata in the LSB and allocyclic processes. It thus provides a foundation for basinwide and inter‐basin sequence‐stratigraphic correlation, allowing future global chemostratigraphic comparisons and providing valuable insights into the synchronicity of geological events.

Ediacaran-Cambrian paleosols of Nevada and California

2025-06-24

Gregory J. Retallack | PLoS ONE

The Cambrian and Ediacaran sequence of California and Nevada is rife with unconformities, paleovalleys, paleosols, and fluvial facies. This study confirms shallow marine environments for grey stromatolitic dolostone and shale … The Cambrian and Ediacaran sequence of California and Nevada is rife with unconformities, paleovalleys, paleosols, and fluvial facies. This study confirms shallow marine environments for grey stromatolitic dolostone and shale of northern localities (Mt Dunfee and Westgard Pass), but fluvial red sandstones and siltstone of southern localities (Johnnie, Eagle Peak, Emigrant Pass, Donna Loy, and Cadiz) include paleosols as evidence for coastal plain and fluvial environments. Three marine transgressions into the southern localities, were in Ediacaran Johnnie Formation, earliest Cambrian Manykodes pedum zone, and Early Cambrian Olenellus trilobite zone. The southern locations have paleosols with Ediacaran fossils Ernietta , Pteridinium , Swartpuntia , and Hallidaya in growth position, as evidence that these vendobiont fossils were non marine. The paleosols include aridland Gypsids and Calcids, as well as weakly developed soils, with diagnostic LYREE enrichment, and low boron content of paleosols. Northern Ediacaran marine rocks, in contrast, are limestones with Cloudina and Wyattia , and shales with Conotubus and Wutubus . Identical marine and non-marine facies and biotas are also known from Ediacaran and Cambrian rocks of Namibia. Ediacaran marine wormlike fossils (Wormworld) were ecologically distinct and geographically separated from non-marine, sessile, vendobionts (Mattressland).

Ediacaran fossils from the Sonia Sandstone, Jodhpur Group, India: New discoveries and interpretations

2025-06-24

S. AHMAD , Sushil K. Pandey | Journal of the Palaeontological Society of India

The Sonia Sandstone of the Jodhpur Group, Marwar Supergroup in western Rajasthan, has unveiled many fossil assemblages, significantly advancing our comprehension of the Ediacaran biotic diversity and palaeoecological dynamics. Recent … The Sonia Sandstone of the Jodhpur Group, Marwar Supergroup in western Rajasthan, has unveiled many fossil assemblages, significantly advancing our comprehension of the Ediacaran biotic diversity and palaeoecological dynamics. Recent field discoveries within the Sonia Sandstone include a diverse suite of Ediacaran fossils, such as Tirasiana qingzhenensis, Hiemalora stellaris, Pteridinium sp., Finkoella ukrainica, Finkoella oblonga, Arumberia banski , coiled form, bizarre form A, Quaestio simpsonorum, and jellyfish-like impressions. These fossils, preserved predominantly as positive epirelief on the bedding plane, exhibit an extraordinary range of morphological intricacies, suggesting a multifaceted and dynamic Ediacaran ecosystem. This unprecedented palaeontological record sheds light on the ecological complexity and evolutionary trajectories during the Ediacaran Period, contributing to the broader understanding of early metazoan diversification and sedimentary biogenic processes.

Signature Specimen: Hemimorphite Pseudomorph after Calcite, Joplin Ore Fields, Missouri, at the Carnegie Museum of Natural History

2025-06-24

Carl A. Francis , Debra L. Wilson , Travis A. Olds | Rocks & Minerals

Constraining 200 million years of geodynamic evolution of the North Alpine foreland at million-year resolution using clumped isotopes and U-Pb dating of diagenetic carbonates

2025-06-24

Nathan Looser , Lukas Aschwanden , Stephan Wohlwend +4 more | Earth and Planetary Science Letters

Mantle-like Sr isotopes in a Sturtian cap carbonate in Oman

2025-06-24

Francis A. Macdonald , Ellery Renger , Adrian Tasistro‐Hart +5 more | Geology

Twice in the Cryogenian Period (720−635 Ma), during the Sturtian and Marinoan glaciations, ice sheets extended to equatorial latitudes for millions of years. These climate extremes have been interpreted to … Twice in the Cryogenian Period (720−635 Ma), during the Sturtian and Marinoan glaciations, ice sheets extended to equatorial latitudes for millions of years. These climate extremes have been interpreted to record the Snowball climate state, in which all of Earth’s oceans were covered with ice. During a Snowball Earth, the hydrological cycle would have been curtailed and silicate weathering greatly reduced. In this scenario, deep ocean chemistry should have evolved toward mantle values through hydrothermal exchange at mid-ocean ridges. Specifically, seawater strontium isotopes (87Sr/86Sr) are predicted to exhibit unradiogenic mantle-like values. However, cap carbonates that overlie the Cryogenian glacial deposits have yielded radiogenic 87Sr/86Sr values similar to those of seawater prior to glaciation, inconsistent with the central geochemical prediction of the Snowball Earth hypothesis. Here we report the discovery of 87Sr/86Sr values of 0.7034 in marine carbonate and authigenic barite that rest directly above Sturtian glacial deposits in Dhofar, Oman. These values record either a local unradiogenic source or Snowball Earth deep-water values that have not been previously identified. If it is a global signal, these new data and geochemical modeling support an extreme Snowball Earth scenario with near-complete ice cover and define one of the largest geochemical perturbations to seawater in Earth history.

An Ediacaran trace-like body fossil of a Palaeopascichnus specimen from Oman under 3D micro-tomography

2025-06-23

André Jorge Pinto , Pedro Álvarez‐Lloret , Ivan Callegari +1 more | Facies

The sediment budget of Great Bahama Bank—Earth’s largest modern carbonate platform

2025-06-23

Cecilia Lopez‐Gamundi , Brian B. Barnes , Christian Betzler +4 more | Geology

Melding remote sensing, field sampling, and seismic data, we broadly quantify the sediment budget of Great Bahama Bank (GBB). This isolated carbonate platform is unique in the modern world because … Melding remote sensing, field sampling, and seismic data, we broadly quantify the sediment budget of Great Bahama Bank (GBB). This isolated carbonate platform is unique in the modern world because of its immense size and its abundance of non-skeletal sediments, making it an analog for the giant platforms of the geologic past. Whereas previous studies focused on singular aspects of the budget, such as sediment production, export, or accumulation, we reconcile all three. We contend that annually, GBB produces 0.93−7.81 × 1013 g of sediment, exports 0.74−8.79 × 1013 g, and accumulates 2.24−57.31 × 1013 g. Cores and seismic data confirm that GBB has tracked rising sea level since flooding 6.7 k.y. ago, necessitating, at minimum and on average, a balanced budget. To perform as such, we contend that the sediment producers atop GBB must have produced at, or near, their maximum modern-day capacity. Our study therefore challenges the notion that non-reefal platforms grossly overproduce sediment. The budget of the Holocene GBB is apparently more precariously balanced than previously thought and may conceivably fail to track future sea-level rise if impeded by changing climate.

Microfacies analysis and diagenetic history of Lower to Middle Eocene carbonates at Umm Russies area in the northeastern desert of Egypt

2025-06-20

Mahmoud Abd-Elhameed , Gamal Attia , Yasser F. Salama +2 more | Scientific Reports

Abstract An integrated study, incorporating field observations and petrographic analysis, has been conducted on the Lower-Middle Eocene carbonates of the Umm Russies area, North Eastern Desert, Egypt. These carbonate sequence … Abstract An integrated study, incorporating field observations and petrographic analysis, has been conducted on the Lower-Middle Eocene carbonates of the Umm Russies area, North Eastern Desert, Egypt. These carbonate sequence represented, from base to top, by Minia, Gebel Hof, and Observatory formations, primarily consisting of marl, dolomite, and limestone. The microfacies analysis allowed the identification of seven distinct microfacies types: bioclastic floatstone, ferruginous dolomite, bioclastic packstone, ferruginous peloidal grainstone, sandy rudstone, foraminiferal wackestone, and bioclastic packstone. These microfacies types reflect a deposition in a wide range of environments from high-energy inner ramp to low-energy middle ramp settings. The performed petrographic analysis indicates that the investigated carbonate rocks underwent significant modification through a range of diagenetic processes, such as micritization, glauconitization, and dolomitization, representing marine-phreatic, meteoric-phreatic, burial, and meteoric-vadose environments. These environments are part of three successive diagenetic stages; eogenesis, mesogenesis, and telogenesis. The relationship between diagenetic episodes and depositional settings highlights that high-energy inner ramp environments facilitated early cementation and micritization, while middle ramp conditions promoted dissolution and neomorphism. Restricted platform margin environments favored dolomitization and glauconitization. Integrating microfacies analysis with these diagenetic interpretations facilitates reconstructing paleoenvironmental conditions and provides a framework for understanding carbonate rock formation in various geological settings.

Enhanced phosphorus regeneration linked to Ediacaran ocean oxygenation

2025-06-20

Dongtao Xu , Xinqiang Wang , Eva Stueeken +5 more | Communications Earth & Environment

Abstract Several pulses of ocean oxygenation events were recognized in the Ediacaran period. However, the intrinsic triggers behind them remain ambiguous. Here we report phosphorus speciation data from the Ediacaran … Abstract Several pulses of ocean oxygenation events were recognized in the Ediacaran period. However, the intrinsic triggers behind them remain ambiguous. Here we report phosphorus speciation data from the Ediacaran Doushantuo Formation, South China, to elucidate the role of recycled phosphorus in driving ocean oxygenation. High ratios of organic carbon to organic phosphorus in all samples relative to the Redfield ratio generally imply preferential release of phosphorus during the remineralization of organic matter. Notably, ratios of organic carbon to reactive phosphorus exceed the Redfield ratio during purported oxygenation intervals, but fall mostly below or close to the Redfield ratio in the rest of the section. Quantitative calculations suggest that enhanced benthic and water-column recycling created a phosphorus influx into the ocean that was comparable to or outpaced that of weathering input. Our study provides empirical evidence for untangling the mechanisms of the Ediacaran oxygenation.

Depositional Controls on ∆′17O Signatures of Sedimentary Sulfate

2025-06-19

P.W. Crockford , Anna R. Waldeck , Andrey Bekker +7 more | Geophysical Research Letters

Abstract Triple oxygen isotope compositions of sedimentary sulfate (∆′ 17 O) have been applied as a tracer of past primary productivity, p O 2 and p CO 2 . However, … Abstract Triple oxygen isotope compositions of sedimentary sulfate (∆′ 17 O) have been applied as a tracer of past primary productivity, p O 2 and p CO 2 . However, large intraformational variability and debate surrounding how such signatures are produced and preserved has limited the understanding of this record. Here we explore what controls ∆′ 17 O signatures of mid‐Proterozoic (ca. 2.0–1.0 Ga) sulfates. We identify a clear depositional control on the magnitude of preserved sulfate ∆′ 17 O signatures, with Proterozoic terrestrial environments preserving the most negative and variable signatures and marine environments displaying values near modern marine sulfate. Our results strongly suggest that local depositional setting influences the magnitude of preserved ∆′ 17 O signals, and that the processes within local environments drive much of the observed intraformational variability. Finally, this analysis suggests that ∆′ 17 O signatures of carbonate associated sulfate in concert with sedimentological observations may offer a powerful tool to identify basin restriction and non‐marine settings throughout the geologic record.

PALEOCLIMATIC, GEOMORPHIC, AND TECTONIC CONTROLS ON PENNSYLVANIAN-PERMIAN COASTAL PLAIN SEDIMENTATION IN PALEOEQUATORIAL PANGEA, PARADOX BASIN, SE UTAH

2025-06-19

Stephanie J. White , Stacy C. Atchley , Gary E. Stinchcomb | Journal of Sedimentary Research

The lower Cutler beds (i.e., Rico and Halgaito Formations) and uppermost Honaker Trail Formation represent the final phase of Paradox Basin sediment fill during the latest Pennsylvanian to Permian and … The lower Cutler beds (i.e., Rico and Halgaito Formations) and uppermost Honaker Trail Formation represent the final phase of Paradox Basin sediment fill during the latest Pennsylvanian to Permian and Late Paleozoic Ice Age (LPIA). Outcrop exposures within the San Juan River canyon near Mexican Hat, Utah record mixed marine and coastal plain deposition across the southwestern shelf of the Paradox Basin. The succession was deposited downwind of a major eolian erg and near the probable terminus of an alluvial fan complex derived from the Uncompahgre Uplift that bounded the Paradox Basin to the northeast. The coastal plain siliciclastics are commonly described as glacially-derived “loess”. However, fine-grained sediments were more likely derived from eolian processes similar to those of modern temperate to subtropical dryland settings due to the paleogeographic position relative to an eolian erg. Paleosols consist of paleoEntisols, paleoInceptisols, and a paleoVertisol and provide clear evidence of a pred ominantly arid to semiarid climate including pedogenic carbonate, eolian-derived detrital carbonate, and minerals consistent with weak chemical weathering. A new cyclostratigraphic approach centered around discontinuity-bound alluvial units (DAUs) is applied to investigate continental depositional cyclicity. The stratal succession provides evidence for possible third-order wetter-drier paleoclimatic shifts based upon assessment of facies proportions, alluvial grain size trends, and inferred depositional processes. Paleosol attributes suggest generally dry conditions during this time, but alluvial grain size trends, resulting from sediment dispersal via fluvial and eolian processes, may suggest shorter-lived periods of increased precipitation, thus highlighting the complicated nature of precipitation patterns for paleoequatorial Pangea prior to establishment of the Pangean monsoon.

THE RECORD OF EDIACARAN BASIN TRANSFORMATION FROM THE DEEPWATER MISTAKEN POINT FORMATION, AVALON TERRANE, NEWFOUNDLAND

2025-06-19

Kieran Thomas Grace , David G. Lowe | Journal of Sedimentary Research

The Mistaken Point Formation is an Ediacaran fossil-bearing deepwater unit exposed in the eastern Avalon terrane of Newfoundland, and was deposited during a basin transformation associated with the shutdown of … The Mistaken Point Formation is an Ediacaran fossil-bearing deepwater unit exposed in the eastern Avalon terrane of Newfoundland, and was deposited during a basin transformation associated with the shutdown of an Ediacaran arc system. Facies and provenance analyses constrain basin morphology, hinterland deformation, and the sedimentologic response of submarine fan systems to this basin transformation, and improve our understanding of the paleoenvironmental and tectonic context of this important Ediacaran fossil-bearing unit. Two distinct submarine fan systems are recognized in the St. John’s region, corresponding to the Middle Cove and Hibbs Cove members. The former is dominated by axial and off-axis submarine lobe strata with radial flow orientations recording submarine fan sedimentation fed transversely by a west-facing slope. The latter is dominated by off-axis, distal, and confined lobe strata with dominant flow to the south–southeast, recording fan sedimentation on a structurally confined south-fa cing slope. The Middle Cove Member to Hibbs Cove Member shift was accompanied by a reduction in fresh volcaniclastic sediment at the expense of quartz, sedimentary, and metamorphic lithic grains. Regional detrital zircon geochronology shows that sediment was derived from erosion of Ediacaran arc rocks, with the Hibbs Cove Member detrital zircon ages indicating an increase in erosion of West Avalonian cover successions and basement, coupled with an increase in zircon from syn-sedimentary igneous activity. Maximum depositional ages suggest that the Middle Cove – Hibbs Cove transition was diachronous, with the switch to delivery of sediment from denuded West Avalonian cover successions beginning in the Mistaken Point region by ca. 565 Ma and progressing north- and eastward over ca. 8 myr. Conversely, a change in paleoflow that records the structural transformation of the basin was synchronous at ca. 557 Ma, resulting in a change from a transversely supplied submarine basin to a south-facing submarine slope. This transformation is interpreted to represent the transition from a backarc basin to a foreland basin, and is compared to the modern Sierra Pampeanas in South America where flat slab subduction during volcanic ridge subduction resulted in craton-ward migration of the arc front and the development of a retroarc foredeep.

Brachiopods and forams reduced calcification costs through morphological simplification during mass extinction events

2025-06-19

Feng‐Yu Wang , Seth Finnegan , Jacopo Dal Corso +7 more | Nature Ecology & Evolution

Revision of Middle Cambrian trilobites and agnostids from Cape Breton Island, Nova Scotia, reveals a Guzhangian faunal interval in the Avalonian cover sequence.

2025-06-19

Stephen R. Westrop , Ed Landing | Canadian Journal of Earth Sciences

The MacLean Brook Group of Cape Breton Island yields a Middle Cambrian trilobite and agnostid fauna that is unlike any other reported from Avalonia. A reassessment of this fauna based … The MacLean Brook Group of Cape Breton Island yields a Middle Cambrian trilobite and agnostid fauna that is unlike any other reported from Avalonia. A reassessment of this fauna based on new and archival collections shows that it includes Hypagnostus cf. H. brevifrons (Angelin) and H. cf. H. confusus (Westergård), Holasaphus centropyge Matthew, Acrocephalaspis matthewi (Hutchinson), and species of Groenwallia Kobayashi and Bailiaspis Resser. It is assigned to an informal biostratigraphic unit, the H. centropyge Fauna. The composition of the H. centropyge Fauna points to a Guzhangian age, and closest similarities lie with the Erratojincella brachymetopa Zone of the Andrarum Limestone of Sweden (Baltica). This zone is correlative with the lower Lejopyge laevigata Zone of Sweden, which defines the base of the Guzhangian. Although the uppermost Guzhangian Agnostus pisiformis Zone is well documented in Avalonia, previous evidence for the basal part of the stage has been limited. Establishment of a Guzhangian age for the MacLean Brook Group in Cape Breton Island is consistent with the age of the group in SE Newfoundland and emphasizes the regional lithostratigraphic unity of the cover sequence of the Avalon terrane. It also provides an upper age constraint on the underlying Gregwa Formation volcanics. To completely bracket the Gregwa biostratigraphically, we also revise "Erratojincella" bretonensis (Hutchinson) from the underlying Dugald Formation, which is consistent with an assignment to the Wuliuan Eccaparadoxides etemenicus Zone.

Sekaninaite (Fe-dominant cordierite) from Devonian S-type rhyolites in Victoria, Australia: genesis and comparisons with other occurrences in volcanic rocks

2025-06-18

W. D. Birch , J. D. Clemens , Matthew Jason Mayne | Mineralogical Magazine

A growth model for the highly abundant Ediacaran tubular organism Funisia dorothea

2025-06-18

Rachel Surprenant , Mary L. Droser | Journal of Paleontology

Abstract Funisia dorothea Droser in Droser and Gehling, 2008 is an inferred metazoan-grade tubular organism, endemic to the Ediacara Member, Rawnsley Quartzite, of South Australia (~555–550 Myr), which is characterized … Abstract Funisia dorothea Droser in Droser and Gehling, 2008 is an inferred metazoan-grade tubular organism, endemic to the Ediacara Member, Rawnsley Quartzite, of South Australia (~555–550 Myr), which is characterized by a hollow, elongate body constructed of uniserially repeating modular elements and is one of the most abundantly reported members of the Ediacara biota. Thus, Funisia Droser in Droser and Gehling, 2008 has broad significance for developing understanding of the Ediacara biota and provides a large dataset for testing hypotheses on the biological traits of Ediacaran tubular organisms. This study investigates size changes in Funisia ’s modular elements to provide further insight into the paleobiology of this organism through the development of a holistic growth model. Results demonstrate that growth in Funisia was highly regulated to maintain uniform modular element width along the length of an individual and, thereby, an overall cylindrical form despite increasing module width throughout ontogeny. The growth model proposed here is compared with the pre-established growth model for another modular Ediacaran tubular organism, Wutubus annularis Chen et al., 2014, demonstrating that the two taxa had distinct growth patterns and disparate autecological strategies, despite a shared constructional morphology.

Paleoenvironment, paleoclimate, and stratigraphy controls on the mineralogy of the Devonian-Carboniferous Ora Formation, Iraq

2025-06-17

Mohammed Sulaiman , Ali I. Al‐Juboury , Ahmed H. Al-Obeidi +5 more | Journal of African Earth Sciences

Microfacies analysis and depositional environment of the Jurassic Antalo Limestone Formation, Blue Nile Basin, Ethiopia

2025-06-17

Beksa Amente , Balemwal Atnafu , Solomon Kassa +1 more | Carbonates and Evaporites

Sequence stratigraphy and geometry of the carbonate platform in the Longwangmiao Formation (Toyonian), Cambrian, SW China

2025-06-17

Guangwei Wang , Haiying Gao , Huayao Zou | Frontiers in Marine Science

Carbonate platforms provide important sedimentary archives for paleoceanography and recording paleoenvironments. The aim of this study was to decipher the control of platform evolution and its constraint on the chemostratigraphic … Carbonate platforms provide important sedimentary archives for paleoceanography and recording paleoenvironments. The aim of this study was to decipher the control of platform evolution and its constraint on the chemostratigraphic correlation in the Lower Cambrian at the eastern part of the Yangtze Platform. With the petrological observation, XRD, as well as C and O isotope analysis, two third-order sequences (SQ1 and SQ2) and six fourthorder sequences (PSQ1, PSQ2, PSQ3, PSQ4, PSQ5, and PSQ6) were recognized in the Longwangmiao Formation. Thirteen lithofacies (Lf-1–Lf-13) and three facies associations (shoreface, upper offshore, and lower offshore) were identified across the proximal to distal range of the platform. The correlation between logged outcrop sections suggested that the carbonate platform evolved from a homoclinal ramp in PSQ1 to a more distally deepened geometry in PSQ2, with this evolution driven by synsedimentary fault activity. From PSQ2 to PSQ3, the geometry evolved from a ramp to a rimmed platform associated with depleted d13C values and an increasing Chemical Index of Alteration (CIA) index. Such a transition of platform geometry may be attributed to the enhanced rate of carbonate production due to intense weathering and nutrient input. The final evolution of the Eastern Yangtze Platform (PSQ4) seemed to have been driven by falling relative sea levels and resulted in the formation of a flat-topped morphology, associated with subaerial exposure and depleted in d13C (LNE2). The two final sequences recognized in outcrops, PSQ5 and PSQ6, were only recognized in the distal reaches of the deposit and were interpreted to be “missed beats” in the sense that the sea level did not transgress the platform top. This study suggests the importance of carbonate production driven by chemical weathering on the control of platform geometry and sequence stratigraphy..

Exploring the Driving Mechanisms Behind Variations in <scp>87Sr</scp>/<scp>86Sr</scp> Ratios in Neoproterozoic–Cambrian Oceans

2025-06-16

Guanghao Peng , Yuyue Han , Bo Ran +3 more | Geological Journal

ABSTRACT The long‐term evolution of seawater strontium isotope ratios ( 87 Sr/ 86 Sr) serves as a critical archive for reconstructing paleogeographic configurations, climatic shifts, and biological evolution. However, the … ABSTRACT The long‐term evolution of seawater strontium isotope ratios ( 87 Sr/ 86 Sr) serves as a critical archive for reconstructing paleogeographic configurations, climatic shifts, and biological evolution. However, the driving mechanisms behind 87 Sr/ 86 Sr variations during the Neoproterozoic–Cambrian transition (700–500 Ma) remain debated, owing to the interplay of multiple geological processes including supercontinental fragmentation, amalgamation, orogenic activity, and volcanic events. This study analyses 486 87 Sr/ 86 Sr measurements from global marine carbonates spanning 700–500 Ma, integrated with temporal records from 89 orogenic belts worldwide. The refined seawater 87 Sr/ 86 Sr curve reveals a three‐phase ascending trend: 700–635 Ma: The breakup of Rodinia and the simultaneous assembly of Gondwana created a low marine 87 Sr/ 86 Sr ratio, yet it still exhibited an upward trend. 635–540 Ma: Progressive ratio increases align with the Gondwana supercontinent assembly, driven by intensified orogenic uplift that exposed radiogenic continental crust to weathering. 540–500 Ma: Accelerated ratio elevation correlates with final Gondwana block amalgamation, volcanic degassing, and greenhouse‐induced climatic conditions that amplified continental silicate weathering fluxes. This phased model highlights pre‐Cambrian orogenesis as a pivotal precursor to the Cambrian Explosion. The convergence of Gondwana continental blocks, coupled with Cambrian greenhouse climates, dramatically enhanced terrestrial weathering efficiency. The resultant surge in nutrient delivery (e.g., phosphorus) to oceans likely created biogeochemical thresholds critical for triggering the Cambrian biospheric radiation. These findings establish tectonically mediated weathering‐climate feedbacks as central regulators of Earth's biogeochemical transitions during this pivotal interval.

The first Ordovician trilobite from Brazil: The dalmanitid Mucronaspis and implications for the glacial Hirnantian in western Gondwana

2025-06-16

Carolina Zabini , Enrique Alberto Randolfe , Juan José Rustán +3 more | Journal of South American Earth Sciences

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2025-06-16

Anastasiia CHUPRYNA , Jérémie Aubineau , Olabode M. Bankole +7 more | Comptes Rendus Géoscience

The Ediacaran to Silurian geological interval of the Podolia Basin, southwestern Ukraine, is associated with significant environmental change and biodiversification of morphologically complex biota. Using a multiproxy approach, including total … The Ediacaran to Silurian geological interval of the Podolia Basin, southwestern Ukraine, is associated with significant environmental change and biodiversification of morphologically complex biota. Using a multiproxy approach, including total Nitrogen (TN), nitrogen and carbon isotopes, total organic matter (TOC), and whole-rock geochemistry, we show that localised and transient nitrate scarcity may have persisted in otherwise oxygenated and nitrate-replete oceans during the period of extensive animal diversification. Bulk δ 15 N bulk data suggest stable partial denitrification between the middle Ediacaran and Silurian, indicating the existence of a large seawater nitrate reservoir in redox stratified waters that sustained the complex biota. Importantly, the switch to climate warming combined with the nitrate-rich waters in the early Paleozoic triggered a rapid phytoplankton and zooplankton bloom. This transition likely supported efficient nutrient flow to higher trophic levels, resulting in an increase in animal body size, biodiversification, and complexity during the Great Ordovician Biodiversification Event. Nonetheless, the upper Ediacaran and upper Silurian strata suggest a progressive near-quantitative denitrification with diazotrophic primary production as the primary nitrogen source. The generated nitrate scarcity was likely transient with no significant biological incidence since the early Paleozoic emergence and diversification of animals in the Podolia Basin are well recorded. The shift to dominant lighter marine sedimentary δ 15 N bulk composition perhaps resulted from the expansion of anoxic conditions in open marine environments during the Silurian sea-level rises and falls.

Multistage fluid activity as a control on the Ediacaran carbonate reservoirs in the Sichuan Basin, SW China

2025-06-14

Tao Luo , Xiaowen Guo , Tiago M. Alves +3 more | Marine and Petroleum Geology

The first record of symbiosis between cornulitids and stromatoporoids from the Hirnantian (Late Ordovician) of Estonia

2025-06-13

Olev Vinn , Magdy El Hedeny , Abdullah A. Alkahtane +1 more | Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen

Correction: The evolution of bone-eating worm diversity in the Upper Cretaceous Chalk Group of the United Kingdom

2025-06-13

Sarah Jamison‐Todd , James D. Witts , Marc E. H. Jones +4 more | PLoS ONE

[This corrects the article DOI: 10.1371/journal.pone.0320945.]. [This corrects the article DOI: 10.1371/journal.pone.0320945.].

Asteroids (Echinodermata) from the Campanian (Upper Cretaceous) rocky shore at Ivö Klack, southern Sweden

2025-06-13

Andrew S. Gale | Acta Geologica Polonica

The asteroid fauna from the upper lower Campanian rocky coastline at Ivö Klack is described, and its palaeoecology is discussed in comparison with other Cretaceous and present-day shallow-marine assemblages. Twenty-six … The asteroid fauna from the upper lower Campanian rocky coastline at Ivö Klack is described, and its palaeoecology is discussed in comparison with other Cretaceous and present-day shallow-marine assemblages. Twenty-six taxa are recorded, belonging predominantly to the Goniasteridae (11 species), with smaller representatives of the families Podosphaerasteridae (4 taxa), Astropectinidae (3 taxa), Forcipulatida (2 taxa), Pterasteridae, Korethrasteridae, Pseudarchasteridae, Pycinasteridae, Asterinidae, and Stauranderasteridae (all one species each). Five new genera are described (Scaniasterina, type species S. surlyki sp. nov.; Granulasterias, type species G. ivoensis sp. nov.; Rugametopaster, type species Metopaster rugissimus Gale, 1987a; Ivoaster, type species I. soerensenae sp. nov. and Vectisaster, type species V. enigmaticus sp. nov.). In addition, new species erected include Astropecten erectus sp. nov., Manfredaster graveseni sp. nov., Metopaster asgaardae sp. nov., Nymphaster macrogranularis sp. nov., N. minigranularis sp. nov., Pycinaster christenseni sp. nov. and Remaster cretaceus sp. nov. Metopaster tamarae Gale, 1987a, is transferred to the genus Weitschataster Neumann and Girod, 2018. The asteroid fauna shows marked similarities to a Cenomanian–Turonian assemblage from rocky shorelines in the Bohemian Basin, Czech Republic, but differs in important respects from present-day shallow-marine asteroid assemblages from around the world.

Mysterious link between Earth’s magnetism and oxygen baffles scientists

2025-06-13

Davide Castelvecchi | Nature

Sequence Development in Relation to Sedimentation History of the Cretaceous–Miocene Cauvery Basin

2025-06-12

Nivedita Chakrabarty , Shilpa Srimani , Indrani Mondal +3 more | CRC Press eBooks

Carbonate sedimentary geochemistry: Influence of sedimentary processes and benthic flux

2025-06-12

Bing Shen , Jitao Chen , Xianguo Lang +4 more | Science China Earth Sciences

Sedimentary and Early Diagenetic Responses to the Huaiyuan Movement During the Early–Middle Ordovician Transition in the Ordos Basin, North China

2025-06-12

Quan Hao , Yu Zhou , Zhanfeng Qiao +6 more | Geosciences

The early Paleozoic Huaiyuan Movement created a major unconformity in the Ordos Basin, significantly influencing sedimentation and early diagenesis in both the overlying and underlying strata near the unconformity. However, … The early Paleozoic Huaiyuan Movement created a major unconformity in the Ordos Basin, significantly influencing sedimentation and early diagenesis in both the overlying and underlying strata near the unconformity. However, the origins of the associated dolomite and silica near this unconformity remain poorly understood. This study aims to reveal how this tectonic event controlled the Early–Middle Ordovician sedimentary environments and early diagenetic processes. The petrological and geochemical results indicate a progressive transition from a dolomitic tidal flat to an intra-platform depression, culminating in a mixed tidal flat during the Early-to-Middle Ordovician, driven by the Huaiyuan Movement. Furthermore, this movement, accompanied by intense weathering and erosion, increased the supply of marine dissolved silica (DSi) and terrestrial nutrients. Consequently, extensive tidal-edge biogenic silica accumulated, which later precipitated as siliceous-cemented dolomite during a shallow-burial stage. We propose a conceptual model of the sedimentary–early diagenetic processes in response to the Huaiyuan Movement, providing novel insights into the regional paleoenvironmental evolution across the Early–Middle Ordovician transition in the Ordos Basin.

Molybdenum isotope records of the Chilpi Group, Bastar Craton, India: Implications on atmospheric and shallow-seawater oxygen content in the Orosirian period

2025-06-12

Prasanta Kumar Mishra , S. Mohanty , Kosuke T. Goto +1 more | Gondwana Research

Cretaceous Belemnites and Other Coleoids of the Cauvery Basin

2025-06-12

А. П. Ипполитов , Ajit Vartak , Zoë Hughes +1 more | CRC Press eBooks

Global Ocean Cycles of Mg, Si, P, N, C, O2 and Fe

2025-06-12

James W. Murray | Oxford University Press eBooks

Abstract This chapter discusses the global cycles of key elements in the Earth’s geochemical system. These cycles are key for understanding what controls the composition of elements in seawater. They … Abstract This chapter discusses the global cycles of key elements in the Earth’s geochemical system. These cycles are key for understanding what controls the composition of elements in seawater. They integrate the basic concepts of aquatic geochemical oceanography and integrate understanding from all the disciplines of oceanography. The starting point for all cycles is the mass balance approach, which consists of the balance between the sources and sinks for the ocean. We distinguish between the cycles for the ocean as a whole and the internal cycles within the ocean. The global geochemical cycles of magnesium, silicon, phosphorus, nitrogen, carbon, oxygen and iron are included.