Download or read book Seasonality Across the Cretaceous paleogene Boundary written by Rachel C. Mohr and published by . This book was released on 2018 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-resolution ontogenetic stable isotope (Îþ18O and Îþ13C) analysis of accretionary carbonate bivalve shells can provide subannual records of their environments. These records present an opportunity to better understand the seasonal variation of past climates and environments. Characterizing the seasonality of past environments is especially helpful in resolving subtle changes during intervals of climate change or environmental perturbations such as during extinction events. Late Cretaceous and early Paleogene bivalve shells of Lahillia larseni from Seymour Island, Antarctica, were isotopically sampled at a high ontogenetic resolution in order to characterize the seasonality of this unstable environment for a period of ~1.3 Myr across the Cretaceous-Paleogene (K-Pg) extinction interval. Ontogenetic ÎþB18O profiles support an austral spring or summer season of growth for L. larseni, with the magnitude of seasonal temperature variation experienced during the growing season ranging from 1.6 ℗ł 0.3℗ʻC to 9.5 ℗ł 0.5℗ʻC (1Ï3). The ontogenetic Îþ13C profiles record isotopic variations in the bottom water dissolved inorganic carbon (DIC) reservoir resulting from the seasonal activity of primary producers. Interannual variations in the primary productivity signal are interpreted as possible evidence for a second bloom of productivity in late summer in years with an additional flux of nutrients, and for the delayed onset of primary productivity in years with winter sea ice. Abnormally low Îþ13C values in ontogenetic carbon isotope profiles with large seasonal variation provide evidence for the seasonal cycling of biogenic methane production and oxidation occurring during a ~180 kyr interval across the K-Pg boundary. Stratigraphic trends reveal a sudden 6.8 ℗ł 1.3℗ʻC (1Ï3) warming event across the K-Pg boundary, with a duration of ~100 kyr, similar to previous estimates of warming across the K-Pg. This study, which presents the highest resolution ontogenetic sampling of L. larseni shells, provides new insights into the seasonality of an unstable paleoenvironment with no modern analogue, and highlights the potential for changes in subannual variability to destabilize an environment during an interval of extinction.

Download or read book Cretaceous Tertiary Mass Extinctions written by Norman MacLeod and published by W. W. Norton. This book was released on 1996-01 with total page 575 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cretaceous-Tertiary Mass Extinctions: Biotic and Environmental Changes is a fascinating new study that combines the most current research on mass extinction with the theoretical perspectives of the leaders in the field. In twenty engaging essays, more than thirty leading paleobiologists and paleontologists uncover a wealth of data from the fossil record about changes in species survival and physical environments across the Cretaceous-Tertiary (K/T) boundary. Together these papers present a much-awaited global perspective on the bilogical and environmental changes taking place during this critical period in the history of life. Anyone interested in the K/T boundary controversy and how research scientists interpret the relationship between climate change and mass extinction will find this work essential.

Download or read book Non dinosaurian Lower Vertebrates Across the Cretaceous Tertiary Boundary in Northeastern Montana written by Laurie J. Bryant and published by Univ of California Press. This book was released on 1989-01-01 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: 00 This study presents current data on vertebrate survival and extinction across the Cretaceous-Tertiary boundary in Montana. Nearly all the common taxa of reptiles (except dinosaurs), amphibians, and fish survived the end of the Cretaceous Period; extinctions were concentrated among rare groups and those found in near-shore habitats. The author concludes that ocean regression and climatic deterioration may explain these selective extinction patterns better than catastrophic hypotheses. This study presents current data on vertebrate survival and extinction across the Cretaceous-Tertiary boundary in Montana. Nearly all the common taxa of reptiles (except dinosaurs), amphibians, and fish survived the end of the Cretaceous Period; extinctions were concentrated among rare groups and those found in near-shore habitats. The author concludes that ocean regression and climatic deterioration may explain these selective extinction patterns better than catastrophic hypotheses.

Download or read book Vegetation and Environmental Changes Across the Cretaceous Paleogene K Pg Boundary in Northeastern Montana written by Paige K. Wilson Deibel and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Cretaceous-Paleogene (K/Pg) mass extinction was a pivotal event in Earth history; not only did this include the global extinction of non-avian dinosaurs but also the local disappearance of as much as 75% of vertebrate and invertebrate species. Our understanding of plants across the K/Pg is comparatively sparse, despite the central role of plants in shaping terrestrial ecosystems and as a food source. This gap in our understanding of plants across this significant time period motivates my study of plants from a ca. 2.3 Myr time interval around the K/Pg in northeastern Montana. Eleven megafloral localities are discussed here in terms of taxonomic affinities and diversity, morphologic diversity, climate implications, and ecological interpretation. This floral assemblage is also compared with contemporaneous fossil assemblages from around the globe. The earliest fossil assemblage in this study, Seafood Salad, is a particularly diverse, angiosperm-dominated flora, interpreted as a “pre-disaster” community from the Late Cretaceous. The taxa at Seafood Salad are commonly unique (15 of 34 taxa are unique to this study), but the flora broadly shows an affinity with floral assemblages from similar stratigraphic intervals in the region, indicating shared regional taxonomy. The K-Pg event in northeastern Montana culminated in the disappearance of 63% of latest Cretaceous taxa and a ~28% drop in richness. Despite the dramatic turnover at the K-Pg boundary, however, the recovery was relatively rapid; early Paleocene floras regained pre-mass extinction levels of richness within 80 to 900 kyr after the boundary. Some aspects of plant ecological diversity (the diversity of ecological strategies) remained restricted, however, and fast-return taxa continued to dominate the floras. Overall, the plant communities in northeastern Montana experienced a significant restructuring (diminishment of dominant functional groups) even though there was no significant loss of ecomorphological richness and taxonomic diversity rebounded relatively quickly. These results point to a pattern of plant community response during biotic crises: ecological changes and diversity loss, short-term taxonomic decline, but few to no major (family-level) taxonomic extinctions. Moreover, this work indicates global and regional heterogeneity in the extinction magnitude and timing of both extinction and recovery across the K-Pg boundary.

Download or read book A Study of Mammalia and Geology Across the Cretaceous tertiary Boundary in Garfield County Montana written by J. David Archibald and published by Univ of California Press. This book was released on 1982-01-01 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Resolving the timing of events around the Cretaceous Paleogene Boundary written by Courtney Jean Sprain and published by . This book was released on 2005 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite decades of study, the exact cause of the Cretaceous-Paleogene boundary (KPB) mass extinction remains contentious. Hypothesized scenarios center around two main environmental perturbations: voluminous (>10^6 km3) volcanic eruptions from the Deccan Traps in modern-day India, and the large impact recorded by the Chicxulub crater. The impact hypothesis has gained broad support, bolstered by the discoveries of iridium anomalies, shocked quartz, and spherules at the KPB worldwide, which are contemporaneous with the Chicxulub impact structure. However, evidence for protracted extinctions, particularly in non-marine settings, and paleoenvironmental change associated with climatic swings before the KPB, challenge the notion that the impact was the sole cause of the KPB mass extinction. Despite forty years of study, the relative importance of each of these events is unclear, and one key inhibitor is insufficient resolution of existing geochronology. In this dissertation, I present work developing a high-precision global chronologic framework for the KPB that outlines the temporal sequence of biotic changes (both within the terrestrial and marine realms), climatic changes, and proposed perturbations (i.e. impact, volcanic eruptions) using 40Ar/39Ar geochronology and paleomagnetism. This work is focused on two major areas of study: 1) refining the timing and tempo of terrestrial ecosystem change around the KPB, and 2) calibrating the geomagnetic polarity timescale, and particularly the timing and duration of magnetic polarity chron C29r (the KPB falls about halfway into C29r). First I develop a high-precision chronostratigraphic framework for fluvial sediments within the Hell Creek region, in NE Montana, which is one of the best-studied terrestrial KPB sections worldwide. For this work I dated 15 tephra deposits with ± 30 ka precision using 40Ar/39Ar geochronology, ranging in time from ~300 ka before the KPB to 1 Ma after. By tying these results to paleontological records, this work is able to constrain the timing of terrestrial faunal decline and recovery in addition to calibrating late Cretaceous and early Paleocene North American Land Mammal Ages biostratigraphy. To aid in global correlation, I next sought to calibrate the timing and duration of C29r. However, based on discrepancies noticed between a calculated duration for C29r, from new dates collected as part of this dissertation and previously published magnetostratigraphy for the Hell Creek region, and the duration provided within the Geologic Time Scale 2012, it became clear that reliability of sediments from the Hell Creek as paleomagnetic recorders was suspect. To test this claim, a complete characterization of the rock magnetic properties of sediments from the Hell Creek region was undertaken. To aid characterization, a new test to determine the presence of intermediate composition titanohematite (Fe2-yTiyO3; 0.5 ≤ y ≤ 0.7) was developed. Results from rock magnetic characterization show that sediments from the Hell Creek should be reliable paleomagnetic recorders, so long as care is taken to remove goethite (a secondary mineral that previous magnetostratigraphic studies in the Hell Creek did not remove), and to avoid samples that have been heated above ~200oC. With the knowledge that sediments from the Hell Creek region are reliable magnetic recorders, I collected 14 new magnetostratigraphic sections, and 18 new high-precision 40Ar/39Ar dates which together provide constraints on the timing and duration of chron C29r, at unprecedented precision. This work enables correlation of our record in the Hell Creek to other KPB records around the globe, in addition to providing a test of the Paleocene astrochronologic timescale.

Download or read book Chemostratigraphy Across Major Chronological Boundaries written by Alcides N. Sial and published by John Wiley & Sons. This book was released on 2018-12-18 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Winner of the 2020 PROSE Award for Earth Science! Exploring environmental changes through Earth’s geological history using chemostratigraphy Chemostratigraphy is the study of the chemical characteristics of different rock layers. Decoding this geochemical record across chronostratigraphic boundaries can provide insights into geological history, past climates, and sedimentary processes. Chemostratigraphy Across Major Chronological Boundaries presents state-of-the-art applications of chemostratigraphic methods and demonstrates how chemical signatures can decipher past environmental conditions. Volume highlights include: Presents a global perspective on chronostratigraphic boundaries Describes how different proxies can reveal distinct elemental and isotopic events in the geologic past Examines the Archaean-Paleoproterozoic, Proterozoic-Paleozoic, Paleozoic-Mesozoic, and Mesozoic-Paleogene boundaries Explores cause-and-effect through major, trace, PGE, and REE elemental, stable, and radiogenic isotopes Offers solutions to persistent chemostratigraphic problems on a micro-global scale Geared toward academic and researchgeoscientists, particularly in the fields of sedimentary petrology, stratigraphy, isotope geology, geochemistry, petroleum geology, atmospheric science, oceanography, climate change and environmental science, Chemostratigraphy Across Major Chronological Boundaries offers invaluable insights into environmental evolution and climatic change. Read the Editors' Vox: https://eos.org/editors-vox/unravelling-the-past-using-elements-and-isotopes

Download or read book The Cretaceous Tertiary boundary interval Raton Basin Colorado and New Mexico and its content of shock metamorphosed minerals Evidence relevant to the K T boundary impact extinction theory written by Glen A. Izett and published by Geological Society of America. This book was released on 1990 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Vegetation of Antarctica through Geological Time written by David J. Cantrill and published by Cambridge University Press. This book was released on 2012-11-22 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fossil history of plant life in Antarctica is central to our understanding of the evolution of vegetation through geological time and also plays a key role in reconstructing past configurations of the continents and associated climatic conditions. This book provides the only detailed overview of the development of Antarctic vegetation from the Devonian period to the present day, presenting Earth scientists with valuable insights into the break up of the ancient supercontinent of Gondwana. Details of specific floras and ecosystems are provided within the context of changing geological, geographical and environmental conditions, alongside comparisons with contemporaneous and modern ecosystems. The authors demonstrate how palaeobotany contributes to our understanding of the paleoenvironmental changes in the southern hemisphere during this period of Earth history. The book is a complete and up-to-date reference for researchers and students in Antarctic paleobotany and terrestrial paleoecology.

Download or read book Carbon and Water Cycle Reconstructions Across the Cretaceous Paleocene Boundary Through Plant Wax Lipids written by Robert Bourque and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The Cretaceous-Paleogene extinction has been one of the most heavily studied mass extinction events from the fossil record, with many aspects from the causation and effect of the extinction having been well studied, but with some areas still not having been explored in great detail. After an extended period of warming, there was a cooling event before the K-Pg extinction occurred that lasted for around 100,000 years, with the Chicxulub impact having been followed by a period of instability where plant communities were recovering. While these have been well studied, changes to the global carbon cycle remain uncertain and changes to the global water cycle have received little attention.By studying the isotopic composition of plant wax lipids preserved in sediments from across the K-Pg boundary, it becomes possible to put together a clearer image of how the carbon and water cycles were behaving up to and across the mass extinction event. These sediments were collected from southern Saskatchewan, Canada, with the lipids having been extracted from the sediments and had the abundance of individual lipid chains and isotopic compositions of hydrogen and carbon measured. Modern plant wax fractionation was used as a basis to relate the isotopic values back to the expected values of atmospheric CO2 and rain water, providing a baseline for the carbon and water cycles and observing how they change across time. Inferences on these cycles show the region was characterized by isotopically light rain water but with no long term trends in water isotope composition, while carbon values show cyclicity reminiscent of Milankovitch orbital cycles, with neither isotope record showing long term effects caused by the extinction, suggesting a relatively rapid recovery of within 10,000 years for both cycles"--

Download or read book Earth History and Palaeogeography written by Trond H. Torsvik and published by Cambridge University Press. This book was released on 2017 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a complete Phanerozoic story of palaeogeography, using new and detailed full-colour maps, to link surface and deep-Earth processes.

Download or read book Sedimentology and extinction patterns across the Cretaceous Tertiary boundary interval in east Texas written by T. HANSEN and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tectonic and Climatic Forcing of Widespread U S Rocky Mountain Conglomerates at the Cretaceous Paleogene Boundary written by Genevive R. Mathers and published by . This book was released on 2009 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: There are a number of distinctive, penecontemporaneous, regionally distributed conglomeratic units in the central and southern U.S. Rocky Mountains whose origin and relationship to regional tectonics, climate change and basin evolution are unclear. These units - the Dark Canyon sequence of the Wasatch Formation in the Book Cliffs of Utah, the Ohio Creek Member of the Mesaverde Group in the Piceance Creek Basin of Colorado, the Arapahoe Conglomerate of the Denver Formation (D1 sequence) in the Denver Basin, the Canaan Peak Formation in the Kaiparowits Plateau of southwestern Utah, and the Ojo Alamo Formation in the San Juan Basin of Colorado and New Mexico - are generally thin and widespread, and abruptly prograde out across underlying units. They are broadly similar in composition, containing dominantly chert and quartzite clasts reworked from local Mesozoic and Paleozoic sources; they were deposited by gravelly river systems; they are unconformity-bounded; and they were all deposited at or around the Cretaceous/Paleogene boundary. While these units have been broadly dated using palynology, interpretation of their origins has been difficult given the scarcity of sample material and the large age ranges for some recovered palynomorphs. Young peak ages of U-Pb detrital zircon spectra, interpreted to represent a maximum depositional age, are used in conjunction with traditional basin analysis techniques and published age data to determine the depositional history of these conglomeratic units. Subsidence analysis indicates that the latest Cretaceous and early Paleogene were times of reduced subsidence rates in these basins, and that the conglomerates were deposited after the initiation of Laramide-related subsidence in these basins, or late-stage Sevier thrusting in the case of the Canaan Peak Formation. While reported ages of deposition of these units cover a large time span, it is permissible that deposition was synchronous between ~66 and ~64 Ma, given the overlap between published ages and U-Pb dates of detrital zircons. The overall similarities in depositional style and timing suggest that gravel dispersal at the Cretaceous/Paleogene boundary could have been a result of regional climate change. Published Global Climate Models and stable isotope studies suggest that the Rocky Mountain monsoon had begun on the eastern flanks of the Sevier belt by the Campanian and had moved east to the broken Laramide foreland by the Paleogene. The depositional model proposed by this study concludes that a period of tectonic quiescence in the rising Laramide uplifts, evidenced by a reduction in subsidence rates and basin-wide unconformities, in latest Cretaceous and early Paleogene time led to overall reduced subsidence rates that, when coupled with an abrupt increase in seasonal precipitation during the Rocky Mountain monsoon, promoted a basinward shift in facies and created erosional surfaces in the proximal parts of basins. Renewed tectonism and subsidence in late Paleocene through Eocene time caused a subsequent retraction of lithofacies, leading to onlap of coarse-grained material (the conglomerates in this study) onto these erosional surfaces and subsequent deposition of finer-grained deposits. Thus, tectonics coupled with climate change lead to the deposition of the widespread conglomerates found around the Cretaceous/Paleogene boundary in the central and southern Rocky Mountains.

Download or read book Paleobiology of the Dinosaurs written by James Orville Farlow and published by Geological Society of America. This book was released on 1989 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Palynology of the Cretaceous Tertiary Boundary in Central Montana U S A and Its Implications for Extraterrestrial Impact written by Carol Louise Hotton and published by . This book was released on 1988 with total page 830 pages. Available in PDF, EPUB and Kindle. Book excerpt: The distribution of pollen and spores across the Cretaceous-Tertiary boundary in Garfield and McCone Counties, Montana was studied to determine whether the pattern of change in vegetation was compatible with a hypothesis of extraterrestrial impact as an agent of extinction. Fifteen sections in the (Cretaceous) Hell Creek and (Tertiary) Tullock Formations, including six boundary sections containing unusually high concentrations of iridium, were examined. Of 291 species of pollen and spores, 45 species of spores, 20 species of gymnosperms and about 225 species of angiosperms were recognized and described in Part II; these constitute the database upon which the statistical analysis in Part I rests

Download or read book Mass Extinctions Volcanism and Impacts written by Thierry Adatte and published by Geological Society of America. This book was released on 2020-04-13 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This volume covers new developments and research on mass extinctions, volcanism, and impacts. It addresses the following topics: the Central Iapetus magmatic province; thermogenic degassing in large igneous provinces; global mercury enrichment in Valanginian sediments; Guerrero-Morelos carbonate platform response to the Caribbean-Colombian Cretaceous large igneous province; implications for the Cretaceous-Paleocene boundary event in shallow platform environments and correlation to the deep sea; environmental effects of Deccan volcanism on biotic transformations and attendant Cretaceous/Paleogene boundary mass extinction in the Indian subcontinent; Deccan red boles; and factors leading to the collapse of producers during the Chicxulub impact and Deccan Traps eruptions"--

Download or read book Establishing Geochemical Constraints on Mass Accumulation Rates Across the Cretaceous Paleogene Boundary with Extraterrestrial Helium 3 written by Marie Minh-Thu Giron and published by . This book was released on 2013 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Records of ocean biogeochemistry in marine sediments show shifts across the Cretaceous-Paleogene boundary (K-Pg) that are simultaneous with the extinction event and onset of the boundary clay deposition. However, the timescale of these records is difficult to determine near the boundary because of fluctuating sedimentation rates and the short duration of the event. In this study, we have used extraterrestrial helium-3 as a constant flux proxy for instantaneous mass accumulation rates in four marine sections: Caravaca, Spain; El Kef, Tunisia; and Hojerup and Kulstirenden, Denmark. These sections are characterized by a thick boundary clay layer and, therefore, are more suitable than many other proxies for high-resolutions studies. In order to better understand the extent of the impact-related perturbations in different paleoenvironments, we performed a high-resolution analysis at Caravaca and lower-resolution analyses at the other three sections. We find that Hojerup and Kulstirenden are not suitable for this analysis due to the probable variation in the flux of extraterrestrial helium-3 as a result of lateral changes in sedimentation rate. Our results suggest that carbonate burial, and likely carbonate production, were more severely affected with increasing paleolatitude. However, the unique depositional environments are probably much more important than just paleolatitude alone. We calculate boundary clay durations of Caravaca and El Kef of 6.45 (h 0.86) kyr and 6.28 (± 1.03) kyr, respectively. These results are consistent with other studies and indicate a uniform, global deposition of the boundary clay and a rapid recovery of carbonate burial in the marine ecosystem after the Cretaceous-Paleogene extinction event.