Palaeoenvironments of the Nordenskjöld Formation: an Antarctic Late Jurassic—Early Cretaceous black shale-tuff sequence

This study documents the palaeoenvironments of a Jurassic-Cretaceous boundary black shale-tuff sequence exposed on the east coast of the Antarctic Peninsula. Sedimentological and palaeontological indices show that, during the deposition of the lower part of the succession, bottom waters were predominantly anaerobic with brief spells of exaerobic or ‘episodically dysaerobic’ conditions. During the deposition of the upper part of the succession, dysaerobic conditions prevailed with mean levels of dissolved oxygen increasing through time. The upward changes seen in the Nordenskjöld Formation are thought to be related to tectonic uplift of the sea floor, through a pycnocline.