Intermittent euxinia in the high-latitude James Ross Basin during the latest Cretaceous and earliest Paleocene

Abstract

Available online xxxx Seymour Island, in the James Ross Basin, Antarctica, contains a continuous succession of latest Cretaceous sediments deposited in a shallow marine environment at high latitude, making it an ideal place to study environmental changes prior to the K-Pg mass extinction. We measured major and trace elements and conducted petrographic analysis of two sections from the Maastrichtian-Danian López de Bertodano Formation of Seymour Island. Several lines of evidence point to intermittently anoxic to euxinic conditions during deposition, including the presence of pyrite framboids with a size distribution suggesting syngenetic formation in the water column, and enrichments in several trace elements, including molybdenum, arsenic, copper, zinc, and chromium. Molybdenum enrichments are clearly associated with enrichments in manganese and authigenic iron, suggesting "shuttling" of redox sensitive trace elements across a chemocline that fluctuated across the sediment-water interface. Comparisons with modern systems suggest relatively high-frequency redox variability, possibly over approximately annual timescales, which may be related to the annual cycle of polar sunlight and associated seasonal changes in primary productivity. Glauconitic horizons are associated with more reducing conditions, including at the K-Pg boundary, though this does not appear to be a uniquely euxinic interval; similar degrees of trace element enrichment are seen in other highly glauconitic intervals. While euxinia may have contributed to low diversity in the lowermost 'Rotularia Units', redox conditions do not seem to have been the primary control on the transition to a mollusc dominated fauna in the latest Maastrichtian. Redox conditions show little to no response to the eruption of the Deccan Traps or Maastrichtian climatic changes. Instead, intermittent euxinia appears to have been a characteristic feature of this high-latitude environment during the Cretaceous-Paleogene transition.

Nature and timing of biotic recovery in Antarctic benthic marine ecosystems following the Cretaceous–Palaeogene mass extinction

“…; Schoepfer et al . ) may have led to the preferential survival, and dominance of infaunal organisms following the extinction horizon in this location. Clapham () found that more motile organisms preferentially survived Mesozoic extinctions, suggesting that greater activity and therefore potentially higher respiratory physiology, controlled survival during extinction periods (Clapham ).…”

“…; Schoepfer et al . ). These indicate that the LBF represents a series of palaeoenvironments, ranging from estuarine to shallow marine (mid‐shelf) (Macellari ; Olivero et al .…”

Bioerosion structures in a Late Cretaceous mosasaur from Antarctica

“…In the case of bioeroded fossil bones, a change in chemical conditions must have occurred during the early burial history of the bone (Trueman and Martill 2002). Intermittent euxinia appears to have been a characteristic feature of this high-latitude environment during the Cretaceous-Paleogene in López de Bertodano Formation (Schoepfer et al 2017). These chemical fluctuations could have inhibited bioerosion and this contributed to the preservation of the histological structures in the analyzed sample.…”

“…These beds represent transgressive shelf deposits followed by a regressive trend in the uppermost part of the López de Bertodano Formation (Olivero 2012). According to Schoepfer et al (2017), several lines of evidence point to intermittently anoxic to euxinic conditions during deposition, including the presence of pyrite framboids with a size distribution suggesting syngenetic formation in the water column.…”

Cretaceous to Paleogene Palinspastic Reconstruction of the East Coast Basin, New Zealand

“…Reduction of organic matter under reducing conditions leads to the formation and preservation of iron pyrite, making S-Fe-TOC relationships particularly informative of paleo-redox conditions and early stage sedimentary diagenesis. A number of trace elements that typically occur in enhanced concentration in organic-rich shales are commonly hosted by pyrite, or other sulphide mineral phases, as well as organic matter (Schoepfer et al, 2017). On this basis, paleo-redox conditions can be assessed by the proportion of S relative to Fe (Raiswell et al, 1988;Lyons & Severmann, 2006;Georgiev et al, 2012).…”