Some recent Mesozoic-related papers:
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Thomas S. Tobin, Jacob W. Honeck, Isabel M. Fendley, Lucas N. Weaver, Courtney J. Sprain, Michael L. Tuite, David T. Flannery, Wade W. Mans & Gregory P. Wilson Mantilla (2021)
Analyzing sources of uncertainty in terrestrial organic carbon isotope data: A case study across the K-Pg boundary in Montana, USA.
Palaeogeography, Palaeoclimatology, Palaeoecology 110451
doi: https://doi.org/10.1016/j.palaeo.2021.110451
https://www.sciencedirect.com/science/article/abs/pii/S0031018221002364
Highlights
Î13Corg values from hand trenches are more positive than those from cores.
Despite trenching, modern contamination/alteration affects Î13Corg values.
Negative Î13Corg excursions are associated with organic rich lithologies.
The K-Pg boundary associated Î13Corg excursion is affected by lithological variation.
Abstract
The Cretaceous-Paleogene boundary (KPB) in the Hell Creek area of Montana is recognized in several places by an iridium anomaly, which is typically identified at or very near the lithological contact between the Hell Creek Formation and the Tullock Member of the Fort Union Formation. Previous work in the area has argued that organic carbon isotope (Î13Corg) excursions can be used for chemostratigraphic correlation within these continental depositional environments, most importantly for the identification of the KPB where impact evidence is unavailable. However, it is unclear how modern surficial weathering affects Î13Corg values, particularly in terrestrial depositional settings, and whether standard sampling methods are sufficient to obtain unaltered rock material. We tested the fidelity of the terrestrial Î13Corg record with respect to surficial alteration and contamination through investigation of different field sampling techniques, including hand trenches, a backhoe-excavated trench, and sediment coring. We find that Î13Corg values in hand and backhoe trenched sections are more positive than Î13Corg values in cored sections, implying that modern surficial alteration affects Î13Corg values but not overall trends. A negative Î13Corg excursion associated with the KPB is present in most sections we analyzed, but it does not appear to be unique within our sections. The KPB excursion occurs within a coal layer, and we observe similar excursions within other carbon-rich lithologies. Given that we cannot disentangle local lithological effects from global atmospheric changes, we conclude that a negative Î13Corg excursion is not an unequivocal indicator of the KPB in the Hell Creek area.
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Yao-feng Cai, Hua Zhang, Chang-qun Cao, Quan-feng Zheng, Chuan-fang Jin & Shu-zhong Shen (2021)
Wildfires and deforestation during the Permian-Triassic transition in the southern Junggar Basin, Northwest China.
Earth-Science Reviews 103670
doi: https://doi.org/10.1016/j.earscirev.2021.103670
https://www.sciencedirect.com/science/article/abs/pii/S0012825221001719
Despite a continuous increase in fossil charcoal records from Late Palaeozoic deposits, which are used as direct evidence for palaeo-wildfires, detailed studies on the charcoal particles are still rare. To investigate the relationship between wildfire activities and the evolution of the terrestrial ecosystem at the end of the Permian, we report on the charcoal recovered from the classic non-marine Permian-Triassic Dalongkou section in Jimsar, Xinjiang Uygur Autonomous Region, Northwest China. Allochthonous and parautochthonous charcoals, identified by both macroscopic and microscopic morphological techniques, were collected from several stratigraphic horizons. These charcoals were classified into 11 categories (which do not represent the taxonomic group) according to their anatomical characteristics and gross morphology. The reflectance values of the charcoals indicate that surface fires were dominant throughout the sequence, with fire regime changing in a distinct interval. The distribution and abundance of all categories and the reflectance of the charcoals suggest that the intensity of wildfires increased in the upper part of the Guodikeng Formation. This trend coincides with the Hg/TOC peaks and a conspicuous excursion in the organic carbon isotope (Î13Corg) values, which may indicate volcanic activities and the disturbance of the carbon cycle that occurred during the Permian-Triassic transition. It is reasonable to infer that the end-Permian mass extinction (EPME) is located at the intensive wildfire interval. The reduction in spore pollen and the decrease in charcoal reflectance hint at a vegetational impoverishment that occurred after this interval. We proposed that increased wildfires, promoted by dry climate conditions and volcanism, aggravated the collapse of the forest ecosystem during the latest Permian.
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Free pdf:
V. I. Davydov and E. V. Karasev (2021)
The Influence of the Permian-Triassic Magmatism in the Tunguska Basin, Siberia on the Regional Floristic Biota of the Permian-Triassic Transition in the Region.
Frontiers in Earth Science 9:635179.
doi: https://doi.org/10.3389/feart.2021.635179
https://www.frontiersin.org/articles/10.3389/feart.2021.635179/full
The end-Permian extinction event (EPEE) considered to have been caused by the eruption of the Siberian Large Igneous Province (SLIP), the age of which is critical for extinction-SLIP model evaluation. The Tunguska Basin flora during this time, in accordance with the EPEE model, supposed to have been killed by the massive injection into the atmosphere of poisonous substances such as methane, sulfates, mercury and massive combustion of coals. In addition, supposed numerous fires presumably devastated the regional flora. However, the diversity of the Tunguska Basin flora drastically increased at the beginning of Induan or slightly earlier and become diverse at the species level in the Olenekian and Anisian, when the main phase of basalt eruption and associated intrusive activity occurred. The overall magmatic activity during the latest Permian and Early Triassic did not kill the flora, but rather stimulate their diversity. The geomagnetic secular variations from the intrusions revealed the similarity of paleomagnetic directions of the Norilsk group layered intrusions with those of the upper Olenekian and lower Anisian Mokulaev and Kharaelakh volcanic formations and intrusions of the Talnakh group with the Olenekian Moronga-Mokulaev formations. The U-Pb dates and the geomagnetic secular variations data expose the obvious discrepancy between these two datasets. The paleomagnetic data suggest that the Norilsk-1 intrusion is younger than the Talnakn and Kharaelakh intrusions, but the U-Pb dates indicate the opposite. The data from layered intrusions in Norilsk and the other regions suggest their prolonged duration and multi-stadial formation. The U-Pb dates from the intrusions of the Norilsk region roughly constrain the onset of the SLIP and generally postdate the end-Permian extinction.
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Lara Sciscio, Timothy J. Broderick, Paul M. Barrett, Darlington Munyikwa, Michel Zondo & Jonah N. Choiniere (2021)
Invertebrate and plant trace fossils from the terrestrial Late Triassic of Zimbabwe.
PALAIOS 36(4): 129â140.
doi: https://doi.org/10.2110/palo.2020.071
https://pubs.geoscienceworld.org/sepm/palaios/article-abstract/36/4/129/596501/INVERTEBRATE-AND-PLANT-TRACE-FOSSILS-FROM-THE
Late Triassic invertebrate and plant trace fossils are described from the Pebbly Arkose Formation of the Upper Karoo Group (Gwembe Sub-basin, Mid-Zambezi Basin), Zimbabwe. These ichnofossils appear in pedogenically modified siltstone and silty mudstone floodplain deposits and overbank fluvial channels. The ichnofossil-bearing sites show variability in their pedogenic features, maturity and preservation. Invertebrate ichnofossils are primarily recorded as horizontal, vertical and inclined burrows, sometimes branched, lined or unlined and may have an active meniscate infill. The common forms documented are Taenidium, Beaconites, Palaeophycus, Skolithos, and Planolites ispp. with some rare and more unusual morphologies (i.e., âYâ-shaped burrow type). Ichnofossil-bearing sites show a low-diversity but high-density of traces commonly dominated by Taenidium and Planolites ispp. The greatest diversity of invertebrate ichnofossils are within interbedded overbank sandstones in weakly pedogenically modified overbank sites. Rhizohalos and rhizoliths are common and often include carbonate infilled roots. Given the abundance and dimensions of fossilized wood and the rhizohalos and rhizoliths, the Pebbly Arkose Formation supported both large and small stature plants. Overall, the studied Pebbly Arkose Formation overbank areas are typically well-drained, calcic palaeosols subject to variable discharge, subaerial exposure, and supporting a diversity of plant and invertebrates tracemakers that lived in a semi-arid to sub-humid environment.
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Free pdf:
Baoxia Du, Mingzhen Zhang, Bainian Sun, Aijing Li, Jing Zhang, Defei Yan, Sanping Xie & Jingyu Wu (2021)
An Exceptionally Well-Preserved Herbaceous Eudicot from the Early Cretaceous (late Aptian-early Albian) of Northwest China.
National Science Review nwab084
doi: https://doi.org/10.1093/nsr/nwab084
https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwab084/6263645
A fossil eudicot, Gansufructus saligna gen. et sp. nov., is reported from the Early Cretaceous (late Aptian-early Albian) of the Gansu Province, Northwest China, based on numerous well-preserved axes with attached leaves and infructescences. The leaves are alternate, short petiolate and linear-lanceolate with low rank pinnate to reticulate venation. The infructescences are loose panicles bearing fruits in different stages of maturity, each containing four partly free carpels borne in a whorled arrangement. Each carpel has three to five seeds borne along its ventral margin. The nature of the leaves and axes indicates a terrestrial, herbaceous habit. In general organization Gansufructus is closely similar to the fruit-bearing axes of Sinocarpus decussatus from the Early Cretaceous Jehol Biota, as well as other more or less contemporaneous angiosperms from the Far East, which together provide evidence of diverse eudicot angiosperms of low stature colonizing areas close to environments of deposition.
Baoxia Du, Mingzhen Zhang, Bainian Sun, Aijing Li, Jing Zhang, Defei Yan, Sanping Xie & Jingyu Wu (2021)
An Exceptionally Well-Preserved Herbaceous Eudicot from the Early Cretaceous (late Aptian-early Albian) of Northwest China.
National Science Review nwab084
doi: https://doi.org/10.1093/nsr/nwab084
https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwab084/6263645
A fossil eudicot, Gansufructus saligna gen. et sp. nov., is reported from the Early Cretaceous (late Aptian-early Albian) of the Gansu Province, Northwest China, based on numerous well-preserved axes with attached leaves and infructescences. The leaves are alternate, short petiolate and linear-lanceolate with low rank pinnate to reticulate venation. The infructescences are loose panicles bearing fruits in different stages of maturity, each containing four partly free carpels borne in a whorled arrangement. Each carpel has three to five seeds borne along its ventral margin. The nature of the leaves and axes indicates a terrestrial, herbaceous habit. In general organization Gansufructus is closely similar to the fruit-bearing axes of Sinocarpus decussatus from the Early Cretaceous Jehol Biota, as well as other more or less contemporaneous angiosperms from the Far East, which together provide evidence of diverse eudicot angiosperms of low stature colonizing areas close to environments of deposition.
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Sietze J. de Graaff, Pim Kaskes, Thomas DÃhais, Steven Goderis, Vinciane Debaille, Catherine H. Ross, Sean P.S. Gulick, Jean-Guillaume Feignon, Ludovic FerriÃre, Christian Koeberl, Jan Smit, Nadine Mattielli & Philippe Claeys (2021)
New insights into the formation and emplacement of impact melt rocks within the Chicxulub impact structure, following the 2016 IODP-ICDP Expedition 364.
GSA Bulletin (advance online publication)
doi: https://doi.org/10.1130/B35795.1
https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35795.1/597003/New-insights-into-the-formation-and-emplacement-of
GSA Bulletin (advance online publication)
doi: https://doi.org/10.1130/B35795.1
https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35795.1/597003/New-insights-into-the-formation-and-emplacement-of
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This study presents petrographic and geochemical characterization of 46 pre-impact rocks and 32 impactites containing and/or representing impact melt rock from the peak ring of the Chicxulub impact structure (YucatÃn, Mexico). The aims were both to investigate the components that potentially contributed to the impact melt (i.e., the pre-impact lithologies) and to better elucidate impact melt rock emplacement at Chicxulub. The impactites presented here are subdivided into two sample groups: the lower impact melt rockâbearing unit, which intrudes the peak ring at different intervals, and the upper impact melt rock unit, which overlies the peak ring. The geochemical characterization of five identified pre-impact lithologies (i.e., granitoid, dolerite, dacite, felsite, and limestone) was able to constrain the bulk geochemical composition of both impactite units. These pre-impact lithologies thus likely represent the main constituent lithologies that were involved in the formation of impact melt rock. In general, the composition of both impactite units can be explained by mixing of the primarily felsic and mafic lithologies, but with varying degrees of carbonate dilution. It is assumed that the two units were initially part of the same impact-produced melt, but discrete processes separated them during crater formation. The lower impact melt rock-earing unit is interpreted to represent impact melt rock injected into the crystalline basement during the compression/excavation stage of cratering. These impact melt rock layers acted as delamination surfaces within the crystalline basement, accommodating its displacement during peak ring formation. This movement strongly comminuted the impact melt rock layers present in the peak ring structure. The composition of the upper impact melt rock unit was contingent on the entrainment of carbonate components and is interpreted to have stayed at the surface during crater development. Its formation was not finalized until the modification stage, when carbonate material would have reentered the crater.
This study presents petrographic and geochemical characterization of 46 pre-impact rocks and 32 impactites containing and/or representing impact melt rock from the peak ring of the Chicxulub impact structure (YucatÃn, Mexico). The aims were both to investigate the components that potentially contributed to the impact melt (i.e., the pre-impact lithologies) and to better elucidate impact melt rock emplacement at Chicxulub. The impactites presented here are subdivided into two sample groups: the lower impact melt rockâbearing unit, which intrudes the peak ring at different intervals, and the upper impact melt rock unit, which overlies the peak ring. The geochemical characterization of five identified pre-impact lithologies (i.e., granitoid, dolerite, dacite, felsite, and limestone) was able to constrain the bulk geochemical composition of both impactite units. These pre-impact lithologies thus likely represent the main constituent lithologies that were involved in the formation of impact melt rock. In general, the composition of both impactite units can be explained by mixing of the primarily felsic and mafic lithologies, but with varying degrees of carbonate dilution. It is assumed that the two units were initially part of the same impact-produced melt, but discrete processes separated them during crater formation. The lower impact melt rock-earing unit is interpreted to represent impact melt rock injected into the crystalline basement during the compression/excavation stage of cratering. These impact melt rock layers acted as delamination surfaces within the crystalline basement, accommodating its displacement during peak ring formation. This movement strongly comminuted the impact melt rock layers present in the peak ring structure. The composition of the upper impact melt rock unit was contingent on the entrainment of carbonate components and is interpreted to have stayed at the surface during crater development. Its formation was not finalized until the modification stage, when carbonate material would have reentered the crater.
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