Molecular proxies as indicators of freshwater incursion-driven salinity stratification

Abstract

Salinity-related stratification in marine environments is one of the main drivers for the development of persistent anoxia and euxinia. It therefore plays a vital role in the sedimentary preservation of organic matter and has also been associated with Oceanic Anoxic Events during several mass extinctions in Earth's history.Here we present a novel molecular proxy using relative abundances of methyltrimethyltridecylchromans (MTTCs) as indicators of riverine freshwater incursions into Middle to Late Devonian paleoreefs exposed to conditions of prevailing anoxia, photic zone euxinia and water column stratification. This paper aims at re-instigating a discussion about the origin of these compounds to potentially broaden their utilization as paleoproxies, adding freshwater stratification to the general salinity reconstructions. The co-variation of MTTC abundance profiles and δ 13 C values with other biomarker parameters in the sediments studied here indicate a link of MTTCs to terrigenous input, pointing towards a previously suggested early diagenetic formation of these compounds from phytol with higher plant-derived alkylphenols.

A stable and productive marine microbial community was sustained through the end‐Devonian Hangenberg Crisis within the Cleveland Shale of the Appalachian Basin, United States

“…The HC decimated ammonoid, trilobite, conodont, and vertebrate taxa, and marked the end of stromatoporoid sponges, though many affected groups recover in the Carboniferous (Caplan & Bustin, 1999;Sallan & Coates, 2010;McGhee et al, 2013). Numerous extinction mechanisms and triggers have been proposed including: oceanwide marine anoxia, volcanism, eustatic change, climate fluctuations (Caplan & Bustin, 1999;Marynowski et al, 2012;Carmichael et al, 2015;Racki, Rakociński, Marynowski, & Wignall, 2018), and the evolution and expansion of land plants (by increasing weathering rates and drawing down CO 2 ; Algeo, Berner, Maynard, & Scheckler, 1995;Tulipani, Grice, Greenwood, Schwark et al, 2015), though there were likely synergistic effects operating that contributed to the ecological crisis. The event was likely rapid (calculated duration of ~50-100 ka; Myrow et al, 2014), marked by glaciation, and globally expressed (Kaiser, Aretz, & Becker, 2015).…”

A new method for the rapid analysis of 1H-Pyrrole-2,5-diones (maleimides) in environmental samples by two-dimensional gas chromatography time-of-flight mass spectrometry

“…Rock samples from the McWhae Ridge (Canning Basin, Western Australia; S 18°43.678 E 126°4.092, WGS84) were studied by [32,45,46]. The samples originate from a core section (MR-1 core; 27.2-42.1 m) which comprises the period between the Late Givetian (Middle Devonian) and the Middle to Late Frasnian (Late Devonian), and were investigated to reveal environmental changes before the Frasnian-Famennian boundary extinction event [32,45].…”

Integrated Stratigraphic Correlation of Upper Devonian Platform-to-Basin Carbonate Sequences, Lennard Shelf, Canning Basin, Western Australia: Advances in Carbonate Margin-to-Slope Sequence Stratigraphy and Stacking Patterns

“…The F-F boundary in the CBCP data set is constrained to an interval that is less than 5.5 m thick in the SO, VHS, and CL measured sections (Appendices 6-8) and has previously been resolved with centimeter precision solely from conodonts (Klapper 2007). The G-F boundary, of lesser importance to this study than the F-F boundary, has virtually no biostratigraphic control but is picked in the lower few meters of the McWhae Ridge Winkie core (MR1; Appendix 11) based on a distinctive biomarker character (Tulipani et al 2014(Tulipani et al , 2015, and in the Guppy Hills measured section (PGH; Appendix 9) based on very poorly constrained vertical successions in coral morphology and assemblage.…”