Peter Carls

Bio: Peter Carls is an academic researcher from Braunschweig University of Technology. The author has contributed to research in topics: Devonian & Conodont. The author has an hindex of 8, co-authored 15 publications receiving 203 citations.

Subdivision of the Lochkovian Stage based on conodont faunas from the stratotype area (Prague Synform, Czech Republic)

Abstract: Relatively rich conodont faunas from sections in the Prague Synform (Barrandian area, Czech Republic) include a number of indexes and other important guide conodonts that can be correlated with other regions, especially with Nevada and the Spanish Central Pyrenees. The collation and detailed correlation of conodont data from the Lochkovian in two parallel sections in the Požary quarries, together with biostratigraphic control of additional data from several (incomplete) sections with changing facies development, is the basis for a new detailed regional biozonal scale for the Lochkovian in the Prague Synform. The new subdivision follows, with modification, the global threefold conodont subdivision of the Lochkovian. Data from the Prague Synform enable further detailed subdivision of the lower, middle and upper Lochkovian into small-scale units. The conodont distribution shows a large proportional discrepancy between the late Lochkovian elsewhere; the conodont record in the latest Lochkovian in the Prague Synform area, which appears to be rather restricted and requires further discussion. Copyright © 2012 John Wiley & Sons, Ltd.

Early Pragian conodont‐based correlations between the Barrandian area and the Spanish Central Pyrenees

Abstract: 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. steinachensis beta morphotype; it enters together with early eognathodontid taxa in the Barrandian sections. These correlations show that routine application of certain zonal concepts can lead to misleading conclusions. Copyright © 2007 John Wiley & Sons, Ltd.

The Silurian Period

Abstract: The Silurian Period (443.1–419.0 Ma) was a time of general convergence of continental plates, strong fluctuations in global sea level, and the early stages of colonization of land. The base of the Silurian System is defined at the level of the first appearance of the graptolite species Akidograptus ascensus at Dob’s Linn, Scotland. Silurian time can be finely resolved using integrated graptolite, conodont, and isotope biochemostratigraphy. The Silurian time scale is based on a CONOP9 composite of graptolite range data derived from 837 stratigraphic sections and 2651 graptolite taxa, with interpolated radioisotope dates, spanning the Ordovician into the Lower Devonian. There is a succession of at least seven globally recognizable positive carbon-isotope excursions, most of which are associated with important bioevents and environmental changes indicated by other geochemical proxies. These data show that the Silurian was a time of dramatic changes in climate, ocean chemistry, and biodiversity.

U-Pb (zircon) age constraints on the timing and duration of Wenlock (Silurian) paleocommunity collapse and recovery during the “Big Crisis”

Abstract: High-precision isotope-dilution U-Pb (zircon) dating was conducted on three volcanic ash fall (bentonite) samples from the Swedish island of Gotland, and on a fourth bentonite from the West Midlands, England. Zircons from the Ireviken, Grotlingbo, Djupvik (Gotland), and Wren's Nest Hill-15 (West Midlands) bentonites yielded weighted mean Pb-206/U-238 ages of 431.83 +/- 0.23/0.67 Ma, 428.45 +/- 035/0.73 Ma, 428.06 +/- 0.2110.66 Ma, and 427.86 +/- 032/0.71 Ma, respectively (analytical/total uncertainties). These biostratigraphically well-controlled age dates effectively bracket the Wenlock Epoch of the Silurian Period and provide control for the duration of one of the major Paleozoic biotic events and associated perturbations to the global carbon cycle (the "Big Crisis" or lundgreni event- graptolites; the NIulde Event-conodonts; the Mulde excursion-carbon isotopes). These new data suggest an older and shorter duration for the recalibration of the Wenlock Series and demonstrate that the cascade of biological and chemical events that took place during the Big Crisis happened on time scales of tens to hundreds of thousands of years. (Less)

Devonian climate, sea level and evolutionary events: an introduction

Abstract: The face of Planet Earth has changed significantly through geological time. Dynamic processes active today, such as plate tectonics and climate change, have shaped the Earth’s surface and impacted biodiversity patterns from the beginning. Organisms, on the other hand, have the capacity to significantly alter Earth’s hydrological and geochemical cycles, its atmosphere and climate, sediments, and even hard rocks deep down under the surface. Abiotic– biotic interactions characterize Earth’s system history and, together with biotic competition and food webs, were the main trigger of evolutionary change, innovations and biodiversity fluctuations. Within the Palaeozoic, the Devonian was an especially interesting time interval as it was characterized by the ‘mid-Paleozoic predator revolution’ (Signor & Brett 1984; Brett 2003) and the related ‘nekton revolution’ (Klug et al. 2010), characterized by the blooms of free-swimming cephalopods, including the oldest ammonoids, and fish groups (e.g. toothed sharks and giant placoderms), the rise of more advanced vertebrates, including the oldest tetrapods (e.g. Blieck et al. 2007, 2010; Niedzwiedzki et al. 2010), the most extensive reef complexes of the Phanerozoic (e.g. Kiessling 2008), and the ‘greening of land’ by the diversification and spread of land plants, including the oldest forests (e.g. Stein et al. 2012; Giesen & Berry 2013), which resulted in new soil types and changing weathering. These major evolutionary trends did not unfold in a long interval of environmental stability, but in times of numerous and repeated, geologically brief, global events that punctuated prolonged periods, up to several million years in duration, of relative stability, termed ecological-evolutionary subunits (EE subunits: Boucot 1990; Brett & Baird 1995; Brett et al. 2009). The bounding events, even those of lesser intensity, produced major re-structuring in local to global ecosystems and are seen as critical drivers of long-term evolutionary patterns (Brett 2012). These linked abiotic and biotic events and extinctions of different magnitude have been summarized by House (1983, 1985, 2002), Walliser (1984, 1996) and, more recently, by Becker et al. (2012). The Devonian event succession is summarized in Figure 1. Two first-order mass extinctions at the Frasnian–Famennian boundary (Kellwasser Crisis) and at the end of the Devonian (Hangenberg Crisis), characterized by the loss of major fossil groups (classes and orders) and complete ecosystems (e.g. metazoan reefs, early forests), have to be viewed in the context of a complex global event sequence. There are important similarities between discrete pulses/phases of the major biotic crises and individual smaller-scale events. In our understanding, second-order global events are characterized by sudden extinctions in many groups and ecosystems, including the complete disappearance of several widespread and diverse organism groups (orders and families). Examples are the basal Emsian atopus Event, where the planktonic graptolites finally died out, the Taghanic Crisis, Frasnes events and Lower Kellwasser Event. Third-order global events show globally elevated extinction rates, often at lower taxonomic level (genera and species), but within many clades and in several ecosystems. Examples are the Silurian–Devonian boundary Klonk Event, and the Daleje, Chotěc, Kacak, Condroz and Annulata events. Fourth-order global extinctions refer to the sudden disappearance of relatively fewer but widespread groups, which implies a global, not regional, trigger. This category may include the Lochkovian–Pragian boundary

Reducing time-scale uncertainty for the Devonian by integrating astrochronology and Bayesian statistics

Abstract: Dealing with uncertainties is inherent to the scientific process. In the process of building geologic time scales, the reported uncertainties are at least as important as the estimates of the numerical ages. Currently all time scales for the Devonian are based on conventional age-depth models, constructed by linear or cubic interpolation between different dated positions. Unfortunately, such models tend to produce overoptimistic confidence intervals. In this study we apply Bayesian statistics to the Devonian time scale to better incorporate stratigraphic and radioisotopic uncertainty. This approach yields a Devonian time scale characterized by increasing uncertainty with growing stratigraphic distance from a radioisotopically dated sample. This feature is absent from The Geologic Time Scale 2012 ; therefore, that time scale is overoptimistic. We further constrain the obtained time scale by incorporating astrochronological duration estimates for the Givetian and Frasnian stages. The combination of radioisotopic dating and astrochronology results in a reduction of the uncertainty on the numerical age of the stage boundaries concerned by several million years. For example, we estimate the age of the Frasnian- Famennian boundary at 373.9 ± 1.4 Ma.