Publications (4)35.89 Total impact
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Article: Coupled carbon isotopic and sedimentological records from the Permian system of eastern Australia reveal the response of atmospheric carbon dioxide to glacial growth and decay during the late Paleozoic Ice Age
Palaeogeography Palaeoclimatology Palaeoecology 01/2010; 286:178-193. · 2.39 Impact Factor -
Article: The Lower Permian Wasp Head Formation, Sydney Basin: high‐latitude, shallow marine sedimentation following the late Asselian to early Sakmarian glacial event in eastern Australia
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ABSTRACT: The Lower Permian Wasp Head Formation (early to middle Sakmarian) is a ∼95 m thick unit that was deposited during the transition to a non-glacial period following the late Asselian to early Sakmarian glacial event in eastern Australia. This shallow marine, sandstone-dominated unit can be subdivided into six facies associations. (i) The marine sediment gravity flow facies association consists of breccias and conglomerates deposited in upper shoreface water depths. (ii) Upper shoreface deposits consist of cross-stratified, conglomeratic sandstones with an impoverished expression of the Skolithos Ichnofacies. (iii) Middle shoreface deposits consist of hummocky cross-stratified sandstones with a trace fossil assemblage that represents the Skolithos Ichnofacies. (iv) Lower shoreface deposits are similar to middle shoreface deposits, but contain more pervasive bioturbation and a distal expression of the Skolithos Ichnofacies to a proximal expression of the Cruziana Ichnofacies. (v) Delta-influenced, lower shoreface-offshore transition deposits are distinguished by sparsely bioturbated carbonaceous mudstone drapes within a variety of shoreface and offshore deposits. Trace fossil assemblages represent distal expressions of the Skolithos Ichnofacies to stressed, proximal expressions of the Cruziana Ichnofacies. Impoverished trace fossil assemblages record variable and episodic environmental stresses possibly caused by fluctuations in sedimentation rates, substrate consistencies, salinity, oxygen levels, turbidity and other physio-chemical stresses characteristic of deltaic conditions. (vi) The offshore transition-offshore facies association consists of mudstone and admixed sandstone and mudstone with pervasive bioturbation and an archetypal to distal expression of the Cruziana Ichnofacies. The lowermost ∼50 m of the formation consists of a single deepening upward cycle formed as the basin transitioned from glacioisostatic rebound following the Asselian to early Sakmarian glacial to a regime dominated by regional extensional subsidence without significant glacial influence. The upper ∼45 m of the formation can be subdivided into three shallowing upward cycles (parasequences) that formed in the aftermath of rapid, possibly glacioeustatic, rises in relative sea-level or due to autocyclic progradation patterns. The shift to a parasequence-dominated architecture and progressive decrease in ice-rafted debris upwards through the succession records the release from glacioisostatic rebound and amelioration of climate that accompanied the transition to broadly non-glacial conditions.Sedimentology 09/2008; 55(5):1517 - 1540. · 2.30 Impact Factor -
Article: CO2-forced climate and vegetation instability during Late Paleozoic deglaciation.
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ABSTRACT: The late Paleozoic deglaciation is the vegetated Earth's only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO2) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO2, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO2 shifts, illustrating the biotic impact associated with past CO2-forced turnover to a permanent ice-free world.Science 02/2007; 315(5808):87-91. · 31.20 Impact Factor -
Article: Stratigraphic imprint of the Late Palaeozoic Ice Age in eastern Australia: a record of alternating glacial and nonglacial climate regime
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2007
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University of Nebraska at Lincoln
- Department of Geosciences
Lincoln, NE, USA -
University of California, Davis
- Department of Geology
Davis, CA, USA
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