Osmium and lithium isotope evidence for weathering feedbacks linked to orbitally paced organic carbon burial and Silurian glaciations
Abstract The Ordovician (∼487 to 443 Ma) ended with the formation of extensive Southern Hemisphere ice sheets, known as the Hirnantian glaciation, and the second largest mass extinction in Earth History. It was followed by the Silurian (∼443 to 419 Ma), one of the most climatically unstable periods of the Phanerozoic as evidenced by several large scale ( > 5 ‰ ) carbon isotope (δ13C) perturbations associated with further extinction events. Despite several decades of research, the cause of these environmental instabilities remains enigmatic. Here, we provide osmium (187Os/188Os) and lithium (δ7Li) isotope measurements of marine sedimentary rocks that cover four Silurian δ13C excursions. Osmi…
Conodonts from Late Devonian island arc settings (Baruunhuurai Terrane, western Mongolia)
Abstract Upper Devonian marine deposits of the Baruunhuurai Terrane in western Mongolia represent island arc settings, which yielded a diverse conodont assemblage of 30 taxa, including species of Ancyrognathus (as well as one new species), Icriodus, Mehlina, Polygnathus and Palmatolepis. Biodiversity analysis of Ancyrognathus, Pelekysgnathus, Mehlina and Icriodus shows that the Mongolian conodont assemblage consists of two endemic and few cosmopolitan taxa. Representatives of the otherwise globally distributed genus Pelekysgnathus are absent. An important factor influencing the regional distribution of conodont taxa seems to be the siliciclastic-dominated sedimentation of the Baruunhuurai T…
Warming or cooling in the Pragian? Sedimentary record and petrophysical logs across the Lochkovian–Pragian boundary in the Spanish Central Pyrenees
Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity betwee…
The middle and upper Lochkovian (Lower Devonian) conodont successions in key peri-Gondwana localities (Spanish Central Pyrenees and Prague Synform) and their relevance for global correlations
Detailed correlation, based on conodont sequences, between middle and upper Lochkovian carbonate successions from two key peri-Gondwanan regions, the Spanish Central Pyrenees and the Prague Synform, is attained for the first time. This correlation facilitates the definition of tie points for further multidisciplinary studies that seek to establish high-resolution temporal subdivision and global correlation. Some intervals have a precision of less than 0.5 Ma, which is significantly greater than in previous studies. The estimated elapsed time considered herein is about 3.2 Ma and is subdivided into five major zones of global scope: transitanstrigonicus, trigonicus-kutscheri, kutscheri-pandor…
Early Pragian conodont-based correlations between the Barrandian area and the Spanish Central Pyrenees
Occurrences and distribution of extremely scarce eognathodontids do not facilitate reliable correlation across the European regions. The correlation of the traditional early Pragian of the Prague Synform (a part of the classical Barrandian area) and the Spanish Central Pyrenees (section Segre 1) is based on conodont taxa of the Icriodus steinachensis and the Pelekysgnathus serratus stocks. This correlation has the potential to be extended to other peri-Gondwanan regions where this scarcity of eognathodontid faunas exists as well. Application of the morphotype subdivision in I. steinachensis enables approximation of the beginning of the Pragian in the Pyrenees. It is based on the entry of I.…