Paleontology

About: Paleontology is a research topic. Over the lifetime, 2 publications have been published within this topic receiving 6 citations. The topic is also known as: palaeontology & palæontology.

Taphonomic concepts for a theoretical biochronology

Abstract: Taphonomy is a conceptual subsystem of paleontology which strives to ascertain how the fossil record has been produced and what sort of modification it has undergone. Taphonomy has its own concepts that allow the fossil record to be dissociated conceptually from the geological or stratigraphicai record. It is also possible to regard fossils (or recorded-entities of different organizational levels) and corresponding organisms (or paleobiologicaJ entities) as being distinct in nature. The aim of taphonomical studies is the fossils, i.e. the recorded·entities, and not the strata that bear them or the paleobiological entities they represent. Taphonomical data are necessary for paleobiological interpretations, and are relevant in applied paleontology. It is necessary, however, to develop a systematic approach to fossils that takes into account logical and epistemological assumptions used in biology and paleobiology. By identifying integrated systems with taphonomicalpaleobiological relationships, new problems in paleontology can be raised and solved. In order to obtain H biochronological framework, it is only necessary to identify and classify systematically into units the different kinds of topologically successive recorded-entities. These concepts are neither incompatible nor contradictory to those in biostratigraphy and chronostratigraphy, and may serve to e lucidate their fundamental basis. [RESUMEN] La Tafonomia es un subsistema conceptual de la Paleontologia cuyo objetivo es averiguar como ha sido producido y que modificaciones ha experimentado el registro fosil. La Tafonomia dispone de conceptos propios que permiten disociar conceptualmente el registro fosil del registro estratigrMico 0 del registro geologico. Tambien es posible considerar como de distinta naturaleza a las fosiles (0 a las entidadesregistradas de diferente nivel de organizacion) y a los correspondientes organismos (0 entidades paleobiologicas). El objeto de estudio en las investigaciones tafonomicas son los fosiles, las entidades registradas, y no los estratos en los que se encuentran 0 las entidades paleobiologicas que representan. Los datos tafon6micos son necesarios para las interpretaciones paleobiol6gicas, y son relevantes en Paleontologia aplicada. Sin embargo, es necesario desarrollar u n planteamiento sistemista para el estudio de 105 f6siles, en el que se tenga en cuenta 105 presupuestos logicos y epistemologicos utilizados en Bioiogia y Paleobiologia. Al identificar sistemas integrados con relaciones tafonomico-paleobiologicas es posible plantear y resolver nuevos problemas en Paleontologia. Para obtener un marco de referencia temporal biocronologico solo es necesario identificar y clasificar sistematicamente en unidades las diferentes clases de entidades-registradas topologicamente sucesivas. Estos conceptos no son incompatibles ni contradictorios con los utilizados en Bioestratigrafia y Cronoestratigrafia, y pueden servir para elucidar los fundamentos teoricos de cada uno de estos sistemas conceptuales.

The rise and demise of the Paleogene Central Tibetan Valley

Abstract: Reconstructing the Paleogene topography and climate of central Tibet informs understanding of collisional tectonic mechanisms and their links to climate and biodiversity. Radiometric dates of volcanic/sedimentary rocks and paleotemperatures based on clumped isotopes within ancient soil carbonate nodules from the Lunpola Basin, part of an east-west trending band of basins in central Tibet and now at 4.7 km, suggest that the basin rose from <2.0 km at 50 to 38 million years (Ma) to >4.0 km by 29 Ma. The height change is quantified using the rates at which wet-bulb temperatures (Tw) decline at land surfaces as those surface rise. In this case, Tw fell from ~8°C at ~38 Ma to ~1°C at 29 Ma, suggesting at least ~2.0 km of surface uplift in ~10 Ma under warm Eocene to Oligocene conditions. These results confirm that a Paleogene Central Tibetan Valley transformed to a plateau before the Neogene.

Paleozoic paleogeography and biogeography.

Abstract: El presente trabajo representa un intento de conciliar los datos que proporcionan sedimentos paleozoicos sensibles a las condiciones paleoclimáticas (tales como carbones, evaporitas y bauxitas), con datos contemporáneos de naturaleza paleobiogeográfica. Como resultado se obtienen algunas reconstrucciones, muy distintas de otras propuestas basadas en el magnetismo residual, que están en mayor consonancia con los conocimientos paleobiogeográficos de que se dispone. An attempt is now being made to reconcile the data of Paleozoic climatically sensitive sediments, such as evaporites, coals, and bauxites, with the contemporary biogeographic data. This attempt results in sorne new paleogeographic reconstructions that are very different from those based on the data of remanent magnetism, and are more consistent with the available biogeographic data.

Age of the oldest known Homo sapiens from eastern Africa

Abstract: Abstract Efforts to date the oldest modern human fossils in eastern Africa, from Omo-Kibish 1–3 and Herto 4,5 in Ethiopia, have drawn on a variety of chronometric evidence, including 40 Ar/ 39 Ar ages of stratigraphically associated tuffs. The ages that are generally reported for these fossils are around 197 thousand years (kyr) for the Kibish Omo I 3,6,7 , and around 160–155 kyr for the Herto hominins 5,8 . However, the stratigraphic relationships and tephra correlations that underpin these estimates have been challenged 6,8 . Here we report geochemical analyses that link the Kamoya’s Hominid Site (KHS) Tuff 9 , which conclusively overlies the member of the Omo-Kibish Formation that contains Omo I, with a major explosive eruption of Shala volcano in the Main Ethiopian Rift. By dating the proximal deposits of this eruption, we obtain a new minimum age for the Omo fossils of 233 ± 22 kyr. Contrary to previous arguments 6,8 , we also show that the KHS Tuff does not correlate with another widespread tephra layer, the Waidedo Vitric Tuff, and therefore cannot anchor a minimum age for the Herto fossils. Shifting the age of the oldest known Homo sapiens fossils in eastern Africa to before around 200 thousand years ago is consistent with independent evidence for greater antiquity of the modern human lineage 10 .