T80 The Early Paleozoic III: Radiations, Extinctions, and Environment

Monday, 16 October 2023
8:00 AM - 12:00 PM
304 / 305

EARLY TO LATE DEVONIAN HIGH-PALEOLATITUDE SEQUENCES FROM THE FALKLAND ISLANDS AND BOLIVIA, SOUTH AMERICA: TRACKING NUTRIENT INFLUX AND ANOXIC EVENTS

Paper number: T80-6
Program: Technical Sessions
Time: 9:10 AM – 9:25 AM

Authors

Abstract

The Devonian period witnessed substantial environmental changes, including the expansion of land plants and subsequent nutrient mobilization. Nutrients transported to the ocean facilitated enhanced nutrient flux, leading to marine anoxic conditions and hypothesized global extinction events. However, most evidence of these events originates from paleotropical regions, leaving polar paleolatitude zones understudied. To address this gap, we present isotopic and geochemical analyses of samples from West Falkland and Bolivia (both South America), to track nutrient influx in high-paleolatitude regions. The Falkland Islands (near paleopolar) and Bolivia (~60° paleosouth), part of the Cape Fold Belt and Chaco Basin, respectively, were located within the cool water Malvinoxhosan (formerly Malvinokaffric) Realm in the southern hemisphere. These sites are correlated with spores, allowing potential links to anoxic events in equatorial areas, particularly those hypothesized as global events. Spanning the late Lochkovian to early Frasnian, strata from these sites encompass the Choteč, Kačák, and Taghanic anoxic events and the migration of the progymnosperm Archaeopteris. The δ13Corg values range from -28.3 to -21.9‰, with distinct alternations between positive and negative carbon isotope excursions. Notably, we observe carbon isotope excursions during the Kačák (+2‰) and Choteč (-1‰) events, similar to those in previous studies, suggesting periods of anoxia comparable to paleotropical regions. Additionally, increased phosphorus/metal ratios and redox-sensitive elements further support the presence of anoxic conditions. By combining data from the Falkland Islands and Bolivia, we aim to enhance our understanding of high-paleolatitude Devonian environments, nutrient influx patterns, and their potential links to global anoxic events. Through a multidisciplinary approach, including chemostratigraphy, geochemical proxies, and paleoenvironmental indicators, our study sheds light on the complex interactions between nutrient cycling, plant expansion, and marine anoxia in these regions.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-396042

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