The late Paleozoic Ice age (LPIA) lasted ~90 million years beginning in South America and possibl... more The late Paleozoic Ice age (LPIA) lasted ~90 million years beginning in South America and possibly Africa during the Mississippian (Visean) and ending in Australia at the end of the Middle Permian (Capitanian). New data suggest that at no time was Gondwana completely covered by ...
The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s h... more The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s history. The end of the LPIA is the only example in Earth’s history where a vegetated and biologically complex Earth transitioned from a bipolar icehouse to a greenhouse state. Recent studies show that LPIA climate changes broadly affected marine invertebrate faunas: glaciations decreased origination and extinction, and long-term, gradual global warming during the final deglaciation altered paleocommunity composition. Regional far-field studies demonstrate that LPIA shallow tropical paleocommunities were stable or weakly distinguishable, and comprised of similar sets of eurytopic taxa. Regional effects of LPIA glaciation and glacial retreat on high paleolatitude (“near-field”) marine biotas have received very little attention. We hypothesized that glacial to post-glacial fluctuations in near-field settings were not conducive for community stability. It was predicted that near glacial marg...
The Pampa de Tepuel and Mojón de Hierro formations in the Tepuel-Genoa Basin (Patagonia) constitu... more The Pampa de Tepuel and Mojón de Hierro formations in the Tepuel-Genoa Basin (Patagonia) constitute a succession that may contain as many as 6 glacimarine and glacially-influenced marine horizons separated by non-glacial intervals. Thus, these strata represent the thickest and most complete record of polar conditions for the Late Paleozoic Ice Age (LPIA). The Lanipustula Biozone is recognized in the Pampa de Tepuel Formation. The Pampa de Tepuel Formation was deposited in a possible shelf edge and slope setting. Coarse clastics would have been introduced into the sites during possible sea level lowstand; while shales were deposited during transgressive and highstand systems tracts. Diamictites are weakly stratified to massive with striated clasts suggesting deposition of fines from meltwater plumes and coarse particles as iceberg rafted debris. Diamictites were also deposited by debris flows. Grooved surfaces are the result of slide/glide planes and possible iceberg keel marks. The ...
The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s h... more The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s history. The end of the LPIA is the only example in Earth’s history where a vegetated and biologically complex Earth transitioned from a bipolar icehouse to a greenhouse state. Recent studies show that LPIA climate changes broadly affected marine invertebrate faunas: glaciations decreased origination and extinction, and long-term, gradual global warming during the final deglaciation altered paleocommunity composition. Regional far-field studies demonstrate that LPIA shallow tropical paleocommunities were stable or weakly distinguishable, and comprised of similar sets of eurytopic taxa. Regional effects of LPIA glaciation and glacial retreat on high paleolatitude (“near-field”) marine biotas have received very little attention. We hypothesized that glacial to post-glacial fluctuations in near-field settings were not conducive for community stability. It was predicted that near glacial marg...
... A major fault, re-ferred to here as the Roderick Valley line-ament, separates predominantly w... more ... A major fault, re-ferred to here as the Roderick Valley line-ament, separates predominantly west-dip-ping slices within and to the west of the fault zone from folded strata in the central and southern part of the range. ... It is 500 m thick west of the Roderick Valley ...
ABSTRACT Two stratigraphically closely spaced bedding planes exposed at Lamping Peak in the Upper... more ABSTRACT Two stratigraphically closely spaced bedding planes exposed at Lamping Peak in the Upper Buckley Formation, Beardmore Glacier area, Antarctica contain abundant in situ stumps (n = 53, n = 21) and other plant fossils that allow reconstruction of forest structure and biomass of Glossopteris forests that thrived at ~75° S paleolatitude in the Permian. Mean trunk diameter is 14 and 25 cm, corresponding to estimatedmeanmaximum heights of 12 and 19 m. Basal areas are 65 and 80m2 ha-1. The above ground biomass was calculated using allometric equations for Ginkgo biloba, yielding biomasses of 147 and 178 Mg ha−1. Biomass estimates based on comparison with biomass of modern forests with equivalent basal areas are higher (225–400 Mg ha−1). The amount of above ground biomass added each year (annual net primary productivity), based on biomass estimates and growth rings in silicified plant material from the Buckley Formation nearby, is poorly constrained, ranging from ~100–2000 g m−2 yr−1. Compared to modern forests at all latitudes, the Permian forests have high basal areas and high biomass, exceeded in both only by forests of the U.S. Pacific northwest and Sequoia forests. The estimated range of productivity (ANPP) is within that of many very productive modern forests. The Lamping Peak forests' basal areas and calculated biomass are also larger than younger high paleolatitude fossil forests except for Arctic Cenozoic forests. The presence of these highly productive fossil forests at high paleolatitude is consistent with hothouse conditions during the Late Permian, prior to the eruption of the Siberian flood basalts.
Putative crayfish trace fossils recently reported from Antarctica are likely small-to large-diame... more Putative crayfish trace fossils recently reported from Antarctica are likely small-to large-diameter burrows of therapsid vertebrates based on comparisons to other Permian and Triassic tetrapod burrows from South Africa. The Small and large-diameter burrows most likely belong to primitive mammal-like reptiles (therapsids) that constructed low-angle, elongate, and sometime spiralling tunnels. Similar burrows with associated therapsid body fossils occur in rocks that were deposited in alluvial environments in basins associated with Gondwana. This exercise in burrow identification stresses the importance of careful analysis of burrow morphologies, both in the outcrop and in the laboratory. Burrow signatures are useful for identifying a burrow architect only when 1) a large data base of specimens is available, 2) outcrop work details the 3-dimensional burrow architecture, and 3) comparisons are made to as many structures of burrowing organisms as possible.
Special Paper of the Geological Society of America
Popular reconstructions of late Paleozoic glaciation depict a single massive ice sheet centered o... more Popular reconstructions of late Paleozoic glaciation depict a single massive ice sheet centered over Victoria Land and extending outward over much of Gondwana. This view is untenable, as interpretations presented here indicate that glaciogenic strata in southern Victoria Land were deposited in a glaciomarine setting, and that ice entered the area from at least two different ice centers on opposite sides of the depositional basin. Reports from other areas also reveal that multiple ice sheets, ice caps, and alpine glaciers diachronously waxed and waned across Gondwana during the Carboniferous and Permian. Glaciogenic rocks of the Lower Permian Metschel Tillite contain glaciotectonic structures and glaciogenic deposits that include (1) sheared diamictites, (2) thrust sheets, (3) massive and stratifi ed diamictites, and (4) sheet sandstones. These features formed as subglacial deforming beds, thrust moraines at glacial termini, and as glaciomarine deposits associated with temperate glac...
FLAIG, Peter P., Bureau of Economic Geology, University of Texas at Austin, Jackson School of Geo... more FLAIG, Peter P., Bureau of Economic Geology, University of Texas at Austin, Jackson School of Geosciences, 10100 Burnet Rd, Austin, TX 78758, peter. flaig@ beg. utexas. edu, ISBELL, John L., Geosciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, and ...
The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s h... more The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s history. The end of the LPIA is the only example in Earth’s history where a vegetated and biologically complex Earth transitioned from a bipolar icehouse to a greenhouse state. Recent studies show that LPIA climate changes broadly affected marine invertebrate faunas: glaciations decreased origination and extinction, and long-term, gradual global warming during the final deglaciation altered paleocommunity composition. Regional far-field studies demonstrate that LPIA shallow tropical paleocommunities were stable or weakly distinguishable, and comprised of similar sets of eurytopic taxa. Regional effects of LPIA glaciation and glacial retreat on high paleolatitude (“near-field”) marine biotas have received very little attention. We hypothesized that glacial to post-glacial fluctuations in near-field settings were not conducive for community stability. It was predicted that near glacial marg...
... Lindsey Henry received geology degrees from Wheaton College (BS) and the University of Wiscon... 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 ...
The Wynyard Formation of Tasmania, Australia, provides the youngest evidence of grounded ice duri... more The Wynyard Formation of Tasmania, Australia, provides the youngest evidence of grounded ice during the Late Carboniferous–Early Permian in the Tasmania Basin of southeastern Gondwana during the late Paleozoic ice age. Within the Wynyard Formation, four facies associations are recognized: 1) massive diamictite, 2) stratified diamictite, 3) conglomerate and sandstone, and 4) deformed mudstone and fine sandstone. A detailed facies analysis was performed in order to interpret the depositional processes and environments. The massive diamictite facies association contains massive diamictite and sandstone and was deposited primarily by iceberg rain-out in a subaqueous morainal bank setting. The stratified diamictite facies association is composed of stratified diamictite, sandstone, and conglomerate, and was deposited by debris flows and iceberg rain-out, and deformed by glacial pushing. The conglomerate and sandstone facies association is made up of cross-stratified, channelized conglome...
Geological Society of America Special Papers, 2010
ABSTRACT The Lower Permian Mackellar Formation is well exposed in a 10,000 km2 outcrop belt in th... more ABSTRACT The Lower Permian Mackellar Formation is well exposed in a 10,000 km2 outcrop belt in the Nimrod, Beardmore, and Shackleton Glacier areas of the Transantarctic Mountains. This formation directly overlies glacial deposits and provides a unique glimpse of high paleolatitude conditions during the last icehouse to greenhouse transition. The unit records deposition in the Mackellar Lake or Inland Sea (MLIS), a fresh-water body at ~80° S paleolatitude that was broadly analogous to Glacial Lake Agassiz and was fi lled by fi ne-grained turbidites. Low total organic carbon (TOC) content and predominant vitrinite and inertinite are consistent with a low infl ux of organic matter from a sparsely vegetated, recently deglaciated terrain. A widespread but low-diversity ichnofauna and variable (although low overall) levels of bioturbation suggest oxic conditions and a bottom fauna restricted to areas of low sedimentation. Integration of sedimentologic, organic geochemical, and paleobiologic information with results of climate models and characteristics of modern lakes enhances reconstruction of parameters that controlled the functioning of the lake as an ecosystem. Regression equations relating mean annual temperature and mean depth of modern lakes to the number of ice-free days applied to the MLIS indicate ice cover from two to fi ve months a year. Estimates of the depth of mixing and depth to the thermocline, based on maximum length, maximum width, and area, suggest a mixing depth of ~50 m and a thermocline of ~20 m. The MLIS probably was stratifi ed during the summer and was dimictic, with overturns occurring after fall cooling and after ice melt; mixing was enhanced by turbidity currents. Productivity was low, as recorded by the low TOC, but organic matter fi xed in the surface water of the lake may have been degraded and not recorded in the sediments. In spite of its high paleolatitude, the MLIS as reconstructed was dynamic and biologically active; the same probably was true of other Permian postglacial lakes. Miller,
ABSTRACT The Mackellar Formation (MF) has been interpreted as a large in-land freshwater lake or ... more ABSTRACT The Mackellar Formation (MF) has been interpreted as a large in-land freshwater lake or sea, though no unequivocal body or ichnofossil evidence has been reported to resolve this question. Fieldwork in 2010–2011 in the MF at Turnabout Ridge along Lowery Glacier and at Mt. Bowers along Beardmore Glacier in the Central Transantarctic Mountains has identified sedimentary successions and trace fossil assemblages most parsimoniously interpreted as fluvio-deltaic shallow marine deposits with salinity stressed ichnofauna. Three-dimensional exposures of the MF at Turnabout Ridge reveal coarsening and thickening upward successions of fissile mudstone, planar to wavy bedded siltstone, and wavy to ripple bedded sandstone, sometimes with hummocky cross stratification, and overlain by compensatorily stacked, lenticular sandstone beds composed of trough cross stratification overlain by ripple laminate, which are in turn truncated by overlying lenticular sandstone beds. Trace fossils include Conichnus, Crossopodia, Gordia, Hormosiroidea, Kouphichnium, Mermia, Planolites, Palaeophycus, Scolicia, and Teichnichnus. Similar lithofacies and ichnofossils are found at Mt. Bowers, particularly an abundance of diminutive Teichichnus and Phycodes. Overall ichnofossil diversity is low but abundant in most beds, whereas burrow and trail diameters are small compared to similar ichnofossils and associated lithofacies in deposits of the same age or younger elsewhere. The interfingering and overlying Fairchild Formation contains a variety of low to high-energy sandstone deposits and contains wood fragments and rhizoliths. Thus, the MF and Fairchild Formation are interpreted as prodelta, delta front, and delta plain environments. At Mt. Bowers, submarine channel-fan deposits are characterized by deeper water channel and levee splays.
The late Paleozoic Ice age (LPIA) lasted ~90 million years beginning in South America and possibl... more The late Paleozoic Ice age (LPIA) lasted ~90 million years beginning in South America and possibly Africa during the Mississippian (Visean) and ending in Australia at the end of the Middle Permian (Capitanian). New data suggest that at no time was Gondwana completely covered by ...
The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s h... more The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s history. The end of the LPIA is the only example in Earth’s history where a vegetated and biologically complex Earth transitioned from a bipolar icehouse to a greenhouse state. Recent studies show that LPIA climate changes broadly affected marine invertebrate faunas: glaciations decreased origination and extinction, and long-term, gradual global warming during the final deglaciation altered paleocommunity composition. Regional far-field studies demonstrate that LPIA shallow tropical paleocommunities were stable or weakly distinguishable, and comprised of similar sets of eurytopic taxa. Regional effects of LPIA glaciation and glacial retreat on high paleolatitude (“near-field”) marine biotas have received very little attention. We hypothesized that glacial to post-glacial fluctuations in near-field settings were not conducive for community stability. It was predicted that near glacial marg...
The Pampa de Tepuel and Mojón de Hierro formations in the Tepuel-Genoa Basin (Patagonia) constitu... more The Pampa de Tepuel and Mojón de Hierro formations in the Tepuel-Genoa Basin (Patagonia) constitute a succession that may contain as many as 6 glacimarine and glacially-influenced marine horizons separated by non-glacial intervals. Thus, these strata represent the thickest and most complete record of polar conditions for the Late Paleozoic Ice Age (LPIA). The Lanipustula Biozone is recognized in the Pampa de Tepuel Formation. The Pampa de Tepuel Formation was deposited in a possible shelf edge and slope setting. Coarse clastics would have been introduced into the sites during possible sea level lowstand; while shales were deposited during transgressive and highstand systems tracts. Diamictites are weakly stratified to massive with striated clasts suggesting deposition of fines from meltwater plumes and coarse particles as iceberg rafted debris. Diamictites were also deposited by debris flows. Grooved surfaces are the result of slide/glide planes and possible iceberg keel marks. The ...
The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s h... more The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s history. The end of the LPIA is the only example in Earth’s history where a vegetated and biologically complex Earth transitioned from a bipolar icehouse to a greenhouse state. Recent studies show that LPIA climate changes broadly affected marine invertebrate faunas: glaciations decreased origination and extinction, and long-term, gradual global warming during the final deglaciation altered paleocommunity composition. Regional far-field studies demonstrate that LPIA shallow tropical paleocommunities were stable or weakly distinguishable, and comprised of similar sets of eurytopic taxa. Regional effects of LPIA glaciation and glacial retreat on high paleolatitude (“near-field”) marine biotas have received very little attention. We hypothesized that glacial to post-glacial fluctuations in near-field settings were not conducive for community stability. It was predicted that near glacial marg...
... A major fault, re-ferred to here as the Roderick Valley line-ament, separates predominantly w... more ... A major fault, re-ferred to here as the Roderick Valley line-ament, separates predominantly west-dip-ping slices within and to the west of the fault zone from folded strata in the central and southern part of the range. ... It is 500 m thick west of the Roderick Valley ...
ABSTRACT Two stratigraphically closely spaced bedding planes exposed at Lamping Peak in the Upper... more ABSTRACT Two stratigraphically closely spaced bedding planes exposed at Lamping Peak in the Upper Buckley Formation, Beardmore Glacier area, Antarctica contain abundant in situ stumps (n = 53, n = 21) and other plant fossils that allow reconstruction of forest structure and biomass of Glossopteris forests that thrived at ~75° S paleolatitude in the Permian. Mean trunk diameter is 14 and 25 cm, corresponding to estimatedmeanmaximum heights of 12 and 19 m. Basal areas are 65 and 80m2 ha-1. The above ground biomass was calculated using allometric equations for Ginkgo biloba, yielding biomasses of 147 and 178 Mg ha−1. Biomass estimates based on comparison with biomass of modern forests with equivalent basal areas are higher (225–400 Mg ha−1). The amount of above ground biomass added each year (annual net primary productivity), based on biomass estimates and growth rings in silicified plant material from the Buckley Formation nearby, is poorly constrained, ranging from ~100–2000 g m−2 yr−1. Compared to modern forests at all latitudes, the Permian forests have high basal areas and high biomass, exceeded in both only by forests of the U.S. Pacific northwest and Sequoia forests. The estimated range of productivity (ANPP) is within that of many very productive modern forests. The Lamping Peak forests' basal areas and calculated biomass are also larger than younger high paleolatitude fossil forests except for Arctic Cenozoic forests. The presence of these highly productive fossil forests at high paleolatitude is consistent with hothouse conditions during the Late Permian, prior to the eruption of the Siberian flood basalts.
Putative crayfish trace fossils recently reported from Antarctica are likely small-to large-diame... more Putative crayfish trace fossils recently reported from Antarctica are likely small-to large-diameter burrows of therapsid vertebrates based on comparisons to other Permian and Triassic tetrapod burrows from South Africa. The Small and large-diameter burrows most likely belong to primitive mammal-like reptiles (therapsids) that constructed low-angle, elongate, and sometime spiralling tunnels. Similar burrows with associated therapsid body fossils occur in rocks that were deposited in alluvial environments in basins associated with Gondwana. This exercise in burrow identification stresses the importance of careful analysis of burrow morphologies, both in the outcrop and in the laboratory. Burrow signatures are useful for identifying a burrow architect only when 1) a large data base of specimens is available, 2) outcrop work details the 3-dimensional burrow architecture, and 3) comparisons are made to as many structures of burrowing organisms as possible.
Special Paper of the Geological Society of America
Popular reconstructions of late Paleozoic glaciation depict a single massive ice sheet centered o... more Popular reconstructions of late Paleozoic glaciation depict a single massive ice sheet centered over Victoria Land and extending outward over much of Gondwana. This view is untenable, as interpretations presented here indicate that glaciogenic strata in southern Victoria Land were deposited in a glaciomarine setting, and that ice entered the area from at least two different ice centers on opposite sides of the depositional basin. Reports from other areas also reveal that multiple ice sheets, ice caps, and alpine glaciers diachronously waxed and waned across Gondwana during the Carboniferous and Permian. Glaciogenic rocks of the Lower Permian Metschel Tillite contain glaciotectonic structures and glaciogenic deposits that include (1) sheared diamictites, (2) thrust sheets, (3) massive and stratifi ed diamictites, and (4) sheet sandstones. These features formed as subglacial deforming beds, thrust moraines at glacial termini, and as glaciomarine deposits associated with temperate glac...
FLAIG, Peter P., Bureau of Economic Geology, University of Texas at Austin, Jackson School of Geo... more FLAIG, Peter P., Bureau of Economic Geology, University of Texas at Austin, Jackson School of Geosciences, 10100 Burnet Rd, Austin, TX 78758, peter. flaig@ beg. utexas. edu, ISBELL, John L., Geosciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, and ...
The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s h... more The late Paleozoic Ice Age (LPIA) has long been known as an important climatic event in Earth’s history. The end of the LPIA is the only example in Earth’s history where a vegetated and biologically complex Earth transitioned from a bipolar icehouse to a greenhouse state. Recent studies show that LPIA climate changes broadly affected marine invertebrate faunas: glaciations decreased origination and extinction, and long-term, gradual global warming during the final deglaciation altered paleocommunity composition. Regional far-field studies demonstrate that LPIA shallow tropical paleocommunities were stable or weakly distinguishable, and comprised of similar sets of eurytopic taxa. Regional effects of LPIA glaciation and glacial retreat on high paleolatitude (“near-field”) marine biotas have received very little attention. We hypothesized that glacial to post-glacial fluctuations in near-field settings were not conducive for community stability. It was predicted that near glacial marg...
... Lindsey Henry received geology degrees from Wheaton College (BS) and the University of Wiscon... 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 ...
The Wynyard Formation of Tasmania, Australia, provides the youngest evidence of grounded ice duri... more The Wynyard Formation of Tasmania, Australia, provides the youngest evidence of grounded ice during the Late Carboniferous–Early Permian in the Tasmania Basin of southeastern Gondwana during the late Paleozoic ice age. Within the Wynyard Formation, four facies associations are recognized: 1) massive diamictite, 2) stratified diamictite, 3) conglomerate and sandstone, and 4) deformed mudstone and fine sandstone. A detailed facies analysis was performed in order to interpret the depositional processes and environments. The massive diamictite facies association contains massive diamictite and sandstone and was deposited primarily by iceberg rain-out in a subaqueous morainal bank setting. The stratified diamictite facies association is composed of stratified diamictite, sandstone, and conglomerate, and was deposited by debris flows and iceberg rain-out, and deformed by glacial pushing. The conglomerate and sandstone facies association is made up of cross-stratified, channelized conglome...
Geological Society of America Special Papers, 2010
ABSTRACT The Lower Permian Mackellar Formation is well exposed in a 10,000 km2 outcrop belt in th... more ABSTRACT The Lower Permian Mackellar Formation is well exposed in a 10,000 km2 outcrop belt in the Nimrod, Beardmore, and Shackleton Glacier areas of the Transantarctic Mountains. This formation directly overlies glacial deposits and provides a unique glimpse of high paleolatitude conditions during the last icehouse to greenhouse transition. The unit records deposition in the Mackellar Lake or Inland Sea (MLIS), a fresh-water body at ~80° S paleolatitude that was broadly analogous to Glacial Lake Agassiz and was fi lled by fi ne-grained turbidites. Low total organic carbon (TOC) content and predominant vitrinite and inertinite are consistent with a low infl ux of organic matter from a sparsely vegetated, recently deglaciated terrain. A widespread but low-diversity ichnofauna and variable (although low overall) levels of bioturbation suggest oxic conditions and a bottom fauna restricted to areas of low sedimentation. Integration of sedimentologic, organic geochemical, and paleobiologic information with results of climate models and characteristics of modern lakes enhances reconstruction of parameters that controlled the functioning of the lake as an ecosystem. Regression equations relating mean annual temperature and mean depth of modern lakes to the number of ice-free days applied to the MLIS indicate ice cover from two to fi ve months a year. Estimates of the depth of mixing and depth to the thermocline, based on maximum length, maximum width, and area, suggest a mixing depth of ~50 m and a thermocline of ~20 m. The MLIS probably was stratifi ed during the summer and was dimictic, with overturns occurring after fall cooling and after ice melt; mixing was enhanced by turbidity currents. Productivity was low, as recorded by the low TOC, but organic matter fi xed in the surface water of the lake may have been degraded and not recorded in the sediments. In spite of its high paleolatitude, the MLIS as reconstructed was dynamic and biologically active; the same probably was true of other Permian postglacial lakes. Miller,
ABSTRACT The Mackellar Formation (MF) has been interpreted as a large in-land freshwater lake or ... more ABSTRACT The Mackellar Formation (MF) has been interpreted as a large in-land freshwater lake or sea, though no unequivocal body or ichnofossil evidence has been reported to resolve this question. Fieldwork in 2010–2011 in the MF at Turnabout Ridge along Lowery Glacier and at Mt. Bowers along Beardmore Glacier in the Central Transantarctic Mountains has identified sedimentary successions and trace fossil assemblages most parsimoniously interpreted as fluvio-deltaic shallow marine deposits with salinity stressed ichnofauna. Three-dimensional exposures of the MF at Turnabout Ridge reveal coarsening and thickening upward successions of fissile mudstone, planar to wavy bedded siltstone, and wavy to ripple bedded sandstone, sometimes with hummocky cross stratification, and overlain by compensatorily stacked, lenticular sandstone beds composed of trough cross stratification overlain by ripple laminate, which are in turn truncated by overlying lenticular sandstone beds. Trace fossils include Conichnus, Crossopodia, Gordia, Hormosiroidea, Kouphichnium, Mermia, Planolites, Palaeophycus, Scolicia, and Teichnichnus. Similar lithofacies and ichnofossils are found at Mt. Bowers, particularly an abundance of diminutive Teichichnus and Phycodes. Overall ichnofossil diversity is low but abundant in most beds, whereas burrow and trail diameters are small compared to similar ichnofossils and associated lithofacies in deposits of the same age or younger elsewhere. The interfingering and overlying Fairchild Formation contains a variety of low to high-energy sandstone deposits and contains wood fragments and rhizoliths. Thus, the MF and Fairchild Formation are interpreted as prodelta, delta front, and delta plain environments. At Mt. Bowers, submarine channel-fan deposits are characterized by deeper water channel and levee splays.
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