Geological Society, London, Special Publications, Feb 16, 2023
In spite of numerous revisions from 1966 to present, the Cantabrian Substage of the Stephanian St... more In spite of numerous revisions from 1966 to present, the Cantabrian Substage of the Stephanian Stage (Pennsylvanian) was never properly defined as a chronostratigraphic unit. Defined and redefined at least three times, the Cantabrian lacks boundary stratotypes that correspond to clear and correlateable biochronological signals. Thus, instead of using a biochronological datum of well-established validity and utility, Cantabrian advocates have relied on ill-defined macrofloral assemblage zones and on lithostratigraphic boundaries to define the substage. As a result, the Cantabrian is demonstrably diachronous, even within Europe; indeed, the Cantabrian has proven to be unusable for correlations outside its type area in northern Spain. To resolve these problems, we recommend that the Cantabrian Substage be abandoned, and the Westphalian–Stephanian boundary be redefined at the major floral turnover that has been documented in the USA, western and central Europe, and in the Donets Basin. We further recommend that the bases of the Kasimovian Series, Stephanian Series, Missourian Series, and Upper Pennsylvanian Series all be aligned with this same floral turnover.
Geological Society, London, Special Publications, Jan 25, 2023
A threshold-like vegetational change in tropical wetlands occurred in the early Kasimovian (the U... more A threshold-like vegetational change in tropical wetlands occurred in the early Kasimovian (the US Desmoinesian–Missourian boundary) – Event 3. Two earlier significant changes occurred, first in the mid-Moscovian (Atokan–Desmoinesian; ∼Bolsovian–Asturian) – Event 1, and the second in the late Moscovian (mid-Desmoinesian; mid-Asturian) – Event 2. These changes occurred during a time period of dynamic and complex physical change in Euramerican Pangaea driven by changes in polar ice volume and accompanying changes in sea level, atmospheric circulation, rainfall, and temperature. During the Event 3 change, hyperbolized as ‘the Carboniferous rainforest collapse’, lycopsid dominance of (mostly peat) swamps changed to marattialean tree-fern and medullosan pteridosperm dominance, and biodiversity decreased. Event 3 encompassed one glacial–interglacial cycle and included vegetational turnover in other wetland habitats. For several subsequent glacial–interglacial cycles peatland dominance varied, known from palynology, before stabilizing. These vegetational changes likely reflect climatic events driving unidirectional, non-reversible wetland vegetational changes, during cooler, wetter parts of glacial–interglacial cycles. Discussion is complicated by different placements of crucial stratigraphic boundaries, but under the same names, compromising both clear communication and understanding of the literature. Not the least is the floating base of the Cantabrian Substage, together with the position of the Westphalian–Stephanian Stage boundary.
We present the first analysis of vegetational change in far western equatorial Pangaea (New Mexic... more We present the first analysis of vegetational change in far western equatorial Pangaea (New Mexico, USA) during the Middle–Late Pennsylvanian transition (determined by conodonts and fusulinids) of the Late Paleozoic Ice Age. The study is based on the largest database assembled from this region: 28 of 44 quantitatively analysed floras from 14 of 26 stratigraphic levels. Most sampled floras are ‘mixed’, both below and above the boundary, including both hygromorphic and mesomorphic/xeromorphic taxa. The taxonomic data were recalibrated morphometrically focusing on foliar traits of lamina width and venation. All data were examined using stratigraphic credible intervals, capture–mark–recapture analyses, and resampling analyses. Results indicate no substantive taxonomic turnover across the boundary. This stands in marked contrast to patterns in mid-Pangaean coal basins where there is a large wetland vegetational turnover. However, plant and physical geological data indicate that immediate...
—Late Middle through Late Pennsylvanian fossil plant assemblages, and the strata from which they ... more —Late Middle through Late Pennsylvanian fossil plant assemblages, and the strata from which they were collected, are described from Socorro County, New Mexico, U.S.A. The flora is diverse and consists of a mixture of taxa generally considered typical of both wetland and seasonally dry habitats. The overall climate likely varied in synchrony with glacial-interglacial cycles, the effects of which were felt across the tropics. However, in the absence of coals and other such indicators of humid climates, it is likely that the climate norms fell between subhumid and arid in this part of the western Pangean continent, which was at the time nearly equatorial. The flora includes the following major taxa: Arborescent lycopsids, Sigillaria, Bergeria, and Asolanus; Calamitalean axes and foliage attributable to Annularia and Asterophyllites; Sphenophyllalean sphenopsids; Marattialean fern foliage mostly unidentifiable but some attributable to either Polymorphopteris or Lobatopteris; a variety of small ferns; medullosan pteridosperms of the genera Alethopteris, Barthelopteris, Charliea; and forms of uncertain affinity, Taeniopteris and Sphenopteris germanica. The flora also contains a variety of reproductive organs, including many types of seeds. Most of the floral elements can be found across tropical Pangea from present-day western North America into the central regions of the supercontinent in present-day Europe. Nearly all of the assemblages are of allochthonous origin, with some rare and notable exceptions, and were deposited in coastal plain to nearshore environments. Thus, most of the plant remains are fragmentary, and many identifications are tentative. Total biodiversity is difficult to estimate due to the vagaries of preservation and disarticulation of the plants, but a rough approximation is somewhere between 50 and 60 species, depending on how determinations are made and on the number of unique but fragmentary specimens that could not be identified with confidence.
This study assesses the feasibility of using deep direct-use (DDU) geothermal energy in agricultu... more This study assesses the feasibility of using deep direct-use (DDU) geothermal energy in agricultural research facilities on the University of Illinois at Urbana-Champaign campus to exploit low-temperature sedimentary basins, such as the Illinois Basin. Subsurface components of the system include extraction and injection wells and downhole pumps. Surface equipment includes heat pumps/exchangers, and fluid transport and monitoring systems. Two geologic formations in the region exhibit a potential as sources for geothermal energy, based on pre initial temperatures and flow rates of fluids. The St. Peter and Mt. Simon Sandstones lie at depths of 634 and 1,280 m, respectively. Geocellular modeling is used to characterize the reservoirs. A St. Peter Sandstone model was made for an area south of the campus. Petrophysical and geothermal properties used are based on data from the closest wells
Geological Society, London, Special Publications, Feb 16, 2023
In spite of numerous revisions from 1966 to present, the Cantabrian Substage of the Stephanian St... more In spite of numerous revisions from 1966 to present, the Cantabrian Substage of the Stephanian Stage (Pennsylvanian) was never properly defined as a chronostratigraphic unit. Defined and redefined at least three times, the Cantabrian lacks boundary stratotypes that correspond to clear and correlateable biochronological signals. Thus, instead of using a biochronological datum of well-established validity and utility, Cantabrian advocates have relied on ill-defined macrofloral assemblage zones and on lithostratigraphic boundaries to define the substage. As a result, the Cantabrian is demonstrably diachronous, even within Europe; indeed, the Cantabrian has proven to be unusable for correlations outside its type area in northern Spain. To resolve these problems, we recommend that the Cantabrian Substage be abandoned, and the Westphalian–Stephanian boundary be redefined at the major floral turnover that has been documented in the USA, western and central Europe, and in the Donets Basin. We further recommend that the bases of the Kasimovian Series, Stephanian Series, Missourian Series, and Upper Pennsylvanian Series all be aligned with this same floral turnover.
Geological Society, London, Special Publications, Jan 25, 2023
A threshold-like vegetational change in tropical wetlands occurred in the early Kasimovian (the U... more A threshold-like vegetational change in tropical wetlands occurred in the early Kasimovian (the US Desmoinesian–Missourian boundary) – Event 3. Two earlier significant changes occurred, first in the mid-Moscovian (Atokan–Desmoinesian; ∼Bolsovian–Asturian) – Event 1, and the second in the late Moscovian (mid-Desmoinesian; mid-Asturian) – Event 2. These changes occurred during a time period of dynamic and complex physical change in Euramerican Pangaea driven by changes in polar ice volume and accompanying changes in sea level, atmospheric circulation, rainfall, and temperature. During the Event 3 change, hyperbolized as ‘the Carboniferous rainforest collapse’, lycopsid dominance of (mostly peat) swamps changed to marattialean tree-fern and medullosan pteridosperm dominance, and biodiversity decreased. Event 3 encompassed one glacial–interglacial cycle and included vegetational turnover in other wetland habitats. For several subsequent glacial–interglacial cycles peatland dominance varied, known from palynology, before stabilizing. These vegetational changes likely reflect climatic events driving unidirectional, non-reversible wetland vegetational changes, during cooler, wetter parts of glacial–interglacial cycles. Discussion is complicated by different placements of crucial stratigraphic boundaries, but under the same names, compromising both clear communication and understanding of the literature. Not the least is the floating base of the Cantabrian Substage, together with the position of the Westphalian–Stephanian Stage boundary.
We present the first analysis of vegetational change in far western equatorial Pangaea (New Mexic... more We present the first analysis of vegetational change in far western equatorial Pangaea (New Mexico, USA) during the Middle–Late Pennsylvanian transition (determined by conodonts and fusulinids) of the Late Paleozoic Ice Age. The study is based on the largest database assembled from this region: 28 of 44 quantitatively analysed floras from 14 of 26 stratigraphic levels. Most sampled floras are ‘mixed’, both below and above the boundary, including both hygromorphic and mesomorphic/xeromorphic taxa. The taxonomic data were recalibrated morphometrically focusing on foliar traits of lamina width and venation. All data were examined using stratigraphic credible intervals, capture–mark–recapture analyses, and resampling analyses. Results indicate no substantive taxonomic turnover across the boundary. This stands in marked contrast to patterns in mid-Pangaean coal basins where there is a large wetland vegetational turnover. However, plant and physical geological data indicate that immediate...
—Late Middle through Late Pennsylvanian fossil plant assemblages, and the strata from which they ... more —Late Middle through Late Pennsylvanian fossil plant assemblages, and the strata from which they were collected, are described from Socorro County, New Mexico, U.S.A. The flora is diverse and consists of a mixture of taxa generally considered typical of both wetland and seasonally dry habitats. The overall climate likely varied in synchrony with glacial-interglacial cycles, the effects of which were felt across the tropics. However, in the absence of coals and other such indicators of humid climates, it is likely that the climate norms fell between subhumid and arid in this part of the western Pangean continent, which was at the time nearly equatorial. The flora includes the following major taxa: Arborescent lycopsids, Sigillaria, Bergeria, and Asolanus; Calamitalean axes and foliage attributable to Annularia and Asterophyllites; Sphenophyllalean sphenopsids; Marattialean fern foliage mostly unidentifiable but some attributable to either Polymorphopteris or Lobatopteris; a variety of small ferns; medullosan pteridosperms of the genera Alethopteris, Barthelopteris, Charliea; and forms of uncertain affinity, Taeniopteris and Sphenopteris germanica. The flora also contains a variety of reproductive organs, including many types of seeds. Most of the floral elements can be found across tropical Pangea from present-day western North America into the central regions of the supercontinent in present-day Europe. Nearly all of the assemblages are of allochthonous origin, with some rare and notable exceptions, and were deposited in coastal plain to nearshore environments. Thus, most of the plant remains are fragmentary, and many identifications are tentative. Total biodiversity is difficult to estimate due to the vagaries of preservation and disarticulation of the plants, but a rough approximation is somewhere between 50 and 60 species, depending on how determinations are made and on the number of unique but fragmentary specimens that could not be identified with confidence.
This study assesses the feasibility of using deep direct-use (DDU) geothermal energy in agricultu... more This study assesses the feasibility of using deep direct-use (DDU) geothermal energy in agricultural research facilities on the University of Illinois at Urbana-Champaign campus to exploit low-temperature sedimentary basins, such as the Illinois Basin. Subsurface components of the system include extraction and injection wells and downhole pumps. Surface equipment includes heat pumps/exchangers, and fluid transport and monitoring systems. Two geologic formations in the region exhibit a potential as sources for geothermal energy, based on pre initial temperatures and flow rates of fluids. The St. Peter and Mt. Simon Sandstones lie at depths of 634 and 1,280 m, respectively. Geocellular modeling is used to characterize the reservoirs. A St. Peter Sandstone model was made for an area south of the campus. Petrophysical and geothermal properties used are based on data from the closest wells
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