- Milwaukee, Wisconsin, United States
Margaret Fraiser
University of Wisconsin Milwaukee, Geosciences, Faculty Member
... Biofilms (an initial phase of cyanobacterial colonization) have been found to contribute little to the stabilization of sediment, whereas mats (mature ... Noffke, N., Hazen, R., and Nhleko, N., 2003, Earth's... more
... Biofilms (an initial phase of cyanobacterial colonization) have been found to contribute little to the stabilization of sediment, whereas mats (mature ... Noffke, N., Hazen, R., and Nhleko, N., 2003, Earth's earliest microbial mats in a siliciclastic marine environment (2.9 Ga Mozaan ...
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Excessive CO2 in the Earth ocean–atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO2 injected into the atmosp.
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A high number of Lazarus taxa and an alleged rarity of silicified faunas during the Early Triassic have been interpretedpreviously as indication that the fossil record following the end-Permian mass extinction is poor and unreliable for... more
A high number of Lazarus taxa and an alleged rarity of silicified faunas during the Early Triassic have been interpretedpreviously as indication that the fossil record following the end-Permian mass extinction is poor and unreliable for palaeontologic studies. This preliminary examination of Early Triassic fossil preservation reveals that silicified faunas are actually moderately common in Lower Triassic strata. Furthermore, an
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A regional field study of ichnocoenoses in the Griesbachian Dinwoody Formation and the Smithian Sinbad Limestone Member revealed that benthic invertebrate tracemaking populations exhibited aspects of opportunistic behaviour following the... more
A regional field study of ichnocoenoses in the Griesbachian Dinwoody Formation and the Smithian Sinbad Limestone Member revealed that benthic invertebrate tracemaking populations exhibited aspects of opportunistic behaviour following the end-Permian mass extinction. This study represents the first documentation of population strategies of ichnocoenoses following a mass extinction event. These trace fossil assemblages are characterised by low-to-moderate ichnodiversity, low-to-moderate bioturbation, small burrow widths, non-specialised behaviour and shallow tiering. Our data combined with other published studies indicate that various ecological characteristics of ichnocoenoses differed by environment, paleolatitude and stage through the Early Triassic. The pattern of opportunistic behaviour is likely attributed to repeated intervals of deleterious environmental conditions similar to those that caused the end-Permian mass extinction.
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Because the end-Permian mass extinction was the largest mass extinction since the Cambrian, numerous studies have focused on taxonomic changes and patterns immediately before and after the Permian/Triassic boundary.This synthesis of... more
Because the end-Permian mass extinction was the largest mass extinction since the Cambrian, numerous studies have focused on taxonomic changes and patterns immediately before and after the Permian/Triassic boundary.This synthesis of paleoecologi- cal data demonstrates that the end-Permian mass extinction and the Early Triassic aftermath were ecologically, as well as taxo- nomically, significant events in the history of life. A
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Written on invitation of the Editorial Board Abstract
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The Kockatea Shale Formation is one of few marine Early Triassic successions recorded in the Gondwana. This formation is exposed at the Northampton area of the northern Perth Basin, Western Australia and was deposited in the Gondwana... more
The Kockatea Shale Formation is one of few marine Early Triassic successions recorded in the Gondwana. This formation is exposed at the Northampton area of the northern Perth Basin, Western Australia and was deposited in the Gondwana interior sea during the Permian and Early Triassic. Trace fossils identified within the Kockatea Shale Formation are extremely abundant and contain 16 ichnogenera (including a problematic ichnogenus). The Gondwanan ichnoassemblage is constrained as late Smithian in age and is the most diverse among coeval ichnofaunas around the world. Several types of grazing traces are also reported for the first time in the Lower Triassic. Several proxies such as bioturbation level, ichnodiversity, burrow size, trace-fossil complexity, and tiring level suggest that tracemakers diversified in the Gondwana interior sea during the late Smithian. The Gondwanan ichnofauna-dominated ecosystem may have reached the ecologic recovery stage 3 of Twitchett's model in late Smithian. The rebound of ichnoassemblages in the aftermath of the end-Permian mass extinction was not controlled by particular environmental settings, all of which however were characterized by oxygenated substrata.► Smithian ichnotaxa from Perth Basin are most diverse among coeval ichnofaunas worldwide. ► Perth Basin ichnotaxa indicate ecosystem recovery after P–Tr extinction in Gondwana. ► Rebound of postextinction ichnoassemblages did not have environmental preference.
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The latest Permian mass extinction (LPE), just prior to the Permian–Triassic boundary at ~ 252 Ma, resulted in the disappearance of ~ 90% of skeletonized marine taxa and the replacement of the Paleozoic Fauna by the Modern Fauna. In the... more
The latest Permian mass extinction (LPE), just prior to the Permian–Triassic boundary at ~ 252 Ma, resulted in the disappearance of ~ 90% of skeletonized marine taxa and the replacement of the Paleozoic Fauna by the Modern Fauna. In the immediate aftermath of the extinction, shallow-marine ecosystems were dominated by microbial communities and diminutive disaster taxa (“Lilliput faunas”), and the post-crisis period in general was characterized by high-abundance, low-diversity marine communities occupying a reduced ecological space. The recovery of marine ecosystems was a protracted process, lasting throughout the ~ 5-Myr-long Early Triassic. Some clades failed to recover and subsequently went extinct (“dead clades walking”), while others recovered only to suffer secondary crises during the Early Triassic. Profound environmental changes accompanied these biotic developments. Deep oceans experienced sustained hypoxia or anoxia for at least several million years following the boundary event. Anoxia was also widespread in shallow-marine areas, especially at the time of the LPE, but it was more episodic and abated more rapidly than in the deep ocean, making it an unlikely factor in the delayed recovery of Early Triassic marine ecosystems. The development of anoxia was due at least in part to a sharp temperature rise following the LPE but may have been stimulated by changes in marine nutrient inventories and productivity rates as well. These conditions may have been the result of a concurrent increase in subaerial weathering rates that was sustained into the Early Triassic. In addition to increasing nutrient fluxes to marine areas, rapid weathering caused a massive influx of sediment to shallow-marine systems, subjecting marine biotas to siltation stress. This scenario implies close teleconnections between terrestrial and marine environments during the Permian–Triassic boundary crisis, with perturbations of the terrestrial realm contributing to the marine crisis.► The P-Tr boundary crisis resulted in ~90% species loss and major ecosystem changes. ► Recovery from the crisis was slow due to recurrent environmental perturbations. ► Anoxic episodes and high fluxes of silt and nutrients harmed shallow-marine systems. ► These conditions resulted from increased rates of subaerial weathering and erosion. ► Changes in weathering were caused by destruction of terrestrial ecosystems.
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A high number of Lazarus taxa and an alleged rarity of silicified faunas during the Early Triassic have been interpretedpreviously as indication that the fossil record following the end-Permian mass extinction is poor and unreliable for... more
A high number of Lazarus taxa and an alleged rarity of silicified faunas during the Early Triassic have been interpretedpreviously as indication that the fossil record following the end-Permian mass extinction is poor and unreliable for palaeontologic studies. This preliminary examination of Early Triassic fossil preservation reveals that silicified faunas are actually moderately common in Lower Triassic strata. Furthermore, an evaluation of environmental and ecological characteristics of the after math of the end-Permian mass extinction indicates that the numerous Early Triassic molds and recrystallized calcareous fossils are at least suitable for palaeoecologic studies. Within this context, future tests with the aim of continuing to examine the potential Early Triassic preservation bias are proposed.
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Unlike the high-abundance, low-diversity macrofaunas that characterize many Early Triassic benthic palaeocommunities, ichnofossils were relatively common in the aftermath of the end-Permian mass extinction worldwide. Ichnofossils... more
Unlike the high-abundance, low-diversity macrofaunas that characterize many Early Triassic benthic palaeocommunities, ichnofossils were relatively common in the aftermath of the end-Permian mass extinction worldwide. Ichnofossils therefore are a good proxy for ecosystem recovery after the end-Permian biotic crisis. This paper documents 14 ichnogenera and one problematic form from Lower Triassic successions exposed in the Lower Yangtze region, South China. Post-extinction ichnodiversity remained rather low throughout the Griesbachian–early Smithian period and abruptly increased in the late Smithian. However, several lines of evidence, including extent of bioturbation, burrow size, trace-fossil complexity, and tiering levels, indicate that diversification of ichnotaxa in the late Smithian did not signal full marine ecosystem recovery from the Permian/Triassic (P/Tr) mass extinction. Marine ichnocoenoses did not recover until the late Spathian in South China. The marginal sea provided hospitable habitats for tracemakers to proliferate in the aftermath of the end-Permian mass extinction.
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... Geology 32, 665-668. McGowan, AJ, 2004b. The effect of the Permo-Triassic bottleneck on Triassic ammonoid morphological evolu-tion. Paleobiology 30, 369-395. ... Science 305, 1760-1763. Newell, ND, Boyd, DW, 1995. Pectinoid bivalves... more
... Geology 32, 665-668. McGowan, AJ, 2004b. The effect of the Permo-Triassic bottleneck on Triassic ammonoid morphological evolu-tion. Paleobiology 30, 369-395. ... Science 305, 1760-1763. Newell, ND, Boyd, DW, 1995. Pectinoid bivalves of the Permian-Triassic crisis. Bull. ...
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The Geological Society of America -- advancing the geosciences, enhancing professional growth, and promoting geosciences in the service of humankind.
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Excessive CO2 in the Earth ocean–atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO2 injected into the atmosphere by the Siberian Traps has been postulated as a major factor leading to the... more
Excessive CO2 in the Earth ocean–atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO2 injected into the atmosphere by the Siberian Traps has been postulated as a major factor leading to the end-Permian mass extinction by facilitating global warming, widespread ocean stratification, and development of anoxic, euxinic and CO2-rich deep waters. A broad incursion of this toxic deep water into the surface ocean may have caused this mass extinction. Although previous studies of the role of excessive CO2 have focused on these “bottom-up” effects emanating from the deep ocean, “top-down” effects of increasing atmosphere CO2 concentrations on ocean-surface waters and biota have not previously been explored. Passive diffusion of atmospheric CO2 into ocean-surface waters decreases the pH and CaCO3 saturation state of seawater, causing a physiological and biocalcification crisis for many marine invertebrates. While both “bottom-up” and “top-down” mechanisms may have contributed to the relatively short-term biotic devastation of the end-Permian mass extinction, such a “top-down” physiological and biocalcification crisis would have had long-term effects and might have contributed to the protracted 5- to 6-million-year-long delay in biotic recovery following this mass extinction. Earth's Modern marine biota may experience similar “top-down” CO2 stresses if anthropogenic input of atmosphere/ocean CO2 continues to rise.
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The Geological Society of America -- advancing the geosciences, enhancing professional growth, and promoting geosciences in the service of humankind.
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The biotic crisis of the Middle Permian through Early Triassic is unmatched in the Phanerozoic in terms of taxonomic diversity losses and paleoecological reorganization. However, the potential taphonomic bias from post-mortem diagenesis... more
The biotic crisis of the Middle Permian through Early Triassic is unmatched in the Phanerozoic in terms of taxonomic diversity losses and paleoecological reorganization. However, the potential taphonomic bias from post-mortem diagenesis for this crucial time has not been evaluated. We assessed the quality of the fossil record during this interval by quantifying the number of Lazarus taxa using our own database, data available in the Paleobiology Database and previous compilations. We also quantitatively tested for ...
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... The recovery interval is characterized by diversification, first from surviving lineages and then by ... environments, while small soft-bodied organisms dominate, gastropods are among the only ... Like Dzulfian (Late Permian)... more
... The recovery interval is characterized by diversification, first from surviving lineages and then by ... environments, while small soft-bodied organisms dominate, gastropods are among the only ... Like Dzulfian (Late Permian) gastropods, many Scythian (Early Triassic) gastropods are ...
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... The recovery interval is characterized by diversification, first from surviving lineages and then by ... environments, while small soft-bodied organisms dominate, gastropods are among the only ... Like Dzulfian (Late Permian)... more
... The recovery interval is characterized by diversification, first from surviving lineages and then by ... environments, while small soft-bodied organisms dominate, gastropods are among the only ... Like Dzulfian (Late Permian) gastropods, many Scythian (Early Triassic) gastropods are ...
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Excessive CO2 in the Earth ocean–atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO2 injected into the atmosphere by the Siberian Traps has been postulated as a major factor leading to the... more
Excessive CO2 in the Earth ocean–atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO2 injected into the atmosphere by the Siberian Traps has been postulated as a major factor leading to the end-Permian mass extinction by facilitating global warming, widespread ocean stratification, and development of anoxic, euxinic and CO2-rich deep waters. A broad incursion
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The Agua de Jagüel Formation near Uspallata, Mendoza Province, Argentina, was deposited within a palaeovalley along the southeastern margin of the Calingasta–Uspallata Basin adjacent to the Protoprecordillera. The basal glacigenic... more
The Agua de Jagüel Formation near Uspallata, Mendoza Province, Argentina, was deposited within a palaeovalley along the southeastern margin of the Calingasta–Uspallata Basin adjacent to the Protoprecordillera. The basal glacigenic sequence of the formation was deposited in the Serpukhovian–Early Bashkirian, near the beginning of the late Palaeozoic ice age. The sequence is composed of diamictite, conglomerate, sandstone, and mudrock and records four depositional stages within a palaeofjord: 1. morainal bank deposition by a wet-based tidewater glacier, 2. glacial retreat succession where ice retreated up the fjord out of the immediate area, allowing iceberg deposition of dropstones and dump deposits, 3. continued glacial retreat with ice receding onto land, allowing a shoreface to develop within the palaeovalley, and 4. transgression across the shoreface and resumption of iceberg deposition. The thickness and facies of this succession are similar to deposits within modern Alaskan fjords housing temperate tidewater glaciers. Comparison of the Agua de Jagüel Formation with Alaskan fjords indicates that sequence stratigraphy used for low latitude deposits must be applied with caution, as glacimarine ice retreat within a fjord produces strata surfaces that are easily misidentified as flooding surfaces resulting from changes in water depth. Likewise, the transgression during stage 4 is significant as it indicates a rise in sea level that occurred during glaciation of the Protoprecordillera, thus suggesting that the transgression between stages 3 and 4 was not driven by input of glacial meltwater. Additionally, the sediment geochemistry suggests that the bottom waters of the palaeovalley were anoxic, which may help explain the absence of bioturbation in the sequence as well as in other ancient glacimarine palaeovalleys. The deglaciation succession and transgression are also recorded in the nearby Hoyada Verde and Tramojo Formations, so it is proposed that all three formations record one glacial event in the Protoprecordillera. Overlying fluvial and shallow marine strata in the Agua de Jagüel, Hoyada Verde, and Tramojo Formations show no indication of continued glaciation in the Protoprecordillera following stage 4 and equivalent strata. The deglaciation succession of the Agua de Jagüel Formation affirms the emerging concept that the late Palaeozoic ice age was characterized by alpine glaciers, ice caps, and small ice sheets that were not massive enough to have driven eustatic fluctuations of 100 m+ as previously understood, and that ice never covered westernmost Gondwana during later LPIA events.
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The biotic crisis of the Middle Permian through Early Triassic is unmatched in the Phanerozoic in terms of taxonomic diversity losses and paleoecological reorganization. However, the potential taphonomic bias from post-mortem diagenesis... more
The biotic crisis of the Middle Permian through Early Triassic is unmatched in the Phanerozoic in terms of taxonomic diversity losses and paleoecological reorganization. However, the potential taphonomic bias from post-mortem diagenesis for this crucial time has not been evaluated. We assessed the quality of the fossil record during this interval by quantifying the number of Lazarus taxa using our own database, data available in the Paleobiology Database and previous compilations. We also quantitatively tested for paleoecological differences between silicified versus non-silicified faunas. Herein we report that there is no major taphonomic bias due to skeletal mineralogy or fossil preservation affecting the Middle and Late Permian fossil record, but that aragonite-shelled molluscs may exhibit a significant Lazarus effect during the Induan. We propose that a variety of mechanisms affected the fossil record of the Paleozoic/Mesozoic transition, including ocean chemistry, paleobiology of the examined groups, and human influences on taxonomic and sampling practices.
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... s). A proliferation of opportunistic organisms has been documented after the end-Cretaceous (Kauffman & Harries ... snails <1 cm in height) proliferated in subtidal marine environments during ... Opportunistic... more
... s). A proliferation of opportunistic organisms has been documented after the end-Cretaceous (Kauffman & Harries ... snails <1 cm in height) proliferated in subtidal marine environments during ... Opportunistic ichnocoenoses following mass extinctions have not yet been identified. ...
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... Lindsey Henry received geology degrees from Wheaton College (BS) and the University of Wisconsin-Milwaukee (MS ... Isbell, JL, Lenaker, PA, Askin, RA, Miller, MF, and Babcock, LE, 2003a, Reevaluation of the timing and extent of late... more
... Lindsey Henry received geology degrees from Wheaton College (BS) and the University of Wisconsin-Milwaukee (MS ... Isbell, JL, Lenaker, PA, Askin, RA, Miller, MF, and Babcock, LE, 2003a, Reevaluation of the timing and extent of late Paleozoic glaciation in Gondwana: Role of ...