Carbon isotopic signature and organic matter composition of cenomanian high-latitude paleosols of southern patagonia

authored by

Augusto Nicolás Varela, María Sol Raigemborn, Patricio Emmanuel Santamarina, Sabrina Lizzoli, Thierry Adatte, Ulrich Heimhofer

Abstract

The Cenomanian Mata Amarilla Formation (MAF) in southern Patagonia (⁓55° S paleolatitude, Austral-Magallanes Basin, Argentina) is composed mainly of stacked fluvial deposits with intercalated paleosols, which document Cenomanian environments at high-paleolatitudes in the Southern Hemisphere. We performed a multiproxy study of the paleosols and sediments of the MAF in order to (1) understand the composition of the soil-and sediment-derived organic matter (OM), (2) apply carbon isotope stratigraphy as a tool to correlate patterns obtained from the MAF with existing marine and non-marine δ¹³Corg records worldwide, and (3) investigate the relationship between variations in spore-pollen assemblages of the MAF and the climatic conditions prevailing in the Cenomanian Southern Hemisphere. An integrated dataset was generated, including total organic carbon content, Rock-Eval pyrolysis data, stable isotope (δ¹³Corg) composition, and palynological data, combined with published paleosol-derived mean annual temperatures and mean annual precipitations. The results indicated that the OM preserved in the MAF paleosols allowed its use as a chemostratigraphic tool. The MAF δ¹³Corg curve showed the rather stable pattern characteristic for the Early to Late Cenomanian interval. The absence of the major positive carbon isotope excursion associated with oceanic anoxic event 2 provided an upper limit for the stratigraphic range of the MAF. The palynological data suggested the development of fern prairies during warmer and moister periods at the expense of the background gymnosperm-dominated forests. Overall, the multiproxy record provided new insights into the long-term environmental conditions during the Cenomanian in the high latitudes of the Southern Hemisphere.

Organisation(s)

Institute of Geology

External Organisation(s)

CONICET
Universidad Nacional de La Plata
Museo Argentino de Ciencias Naturales Bernardino Rivadavia
University of Lausanne (UNIL)

Type

Article

Journal

Geosciences (Switzerland)

Volume

11

Publication date

08.09.2021

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General Earth and Planetary Sciences

Sustainable Development Goals

SDG 14 - Life Below Water

Electronic version(s)

https://doi.org/10.3390/geosciences11090378 (Access: Open)