The Albian–Cenomanian transition and Oceanic Anoxic Event 1d – an example from the Boreal Realm

Abstract

The upper Albian to lower Cenomanian interval in the Hanover area (Germany) is characterized by a well-developed lithological transition from upper Albian monotonous (marly) claystones of several hundred metres thickness, which become enriched in biosilica in the topmost Albian, to increasingly CaCO 3 -rich marls and limestones in the lower and middle Cenomanian. This study presents a new 165 m thick composite record spanning the latest Albian to mid-early Cenomanian (ca 103Á0 to 97Á5 Ma) based on two core drillings at Anderten in the central Lower Saxony Basin (east of Hanover), which is a sub-basin of the North German Basin. Due to the lack or delayed occurrences of Tethyan biostratigraphic markers for the late Albian and early Cenomanian in the Boreal Realm, the definition of the Albian-Cenomanian boundary, as based on the lowest occurrence of Thalmanninella globotruncanoides, is not applicable. In order to overcome this issue, an integrated biostratigraphic-chemostratigraphic approach has been employed. In addition to biostratigraphy (calcareous nannofossils, ostracods, planktonic foraminifera and inoceramids), the Anderten succession has been studied using sedimentary geochemistry (CaCO 3 , total organic carbon, d 13 C and d 18 O), c-ray logging and X-ray fluorescence core scanning. This approach enabled successful correlation of the composite Anderten record to European reference sections in England, south-east France and Italy, as well as to further low-resolution records from the Lower Saxony Basin (Wunstorf and Konrad 101 core). This work has made it possible to identify the d 13 C carb expression of: (i) the Oceanic Anoxic Event 1d; (ii) the Albian-Cenomanian boundary interval; and (iii) potentially the Lower Cenomanian Event(s). Chemostratigraphic age assignments are supported by biostratigraphic results. Calcareous nannofossils indicate an extended Upper Cretaceous 0 (UC0) zone (upper Albian) up to Upper Cretaceous 2 (UC2; upper lower Cenomanian), and the occurrence of the ostracod Physocythere steghausi supports an early Cenomanian age for most of the upper part of the composite record. Notably, influxes of the planktonic foraminifer Thalmanninella aff. reicheli 44 have previously been described from this area and the first appearance of this taxon is usually used to define the base of the middle Cenomanian Substage. However, findings from the Anderten cores and elsewhere suggest that this taxon has an apparently earlier first appearance, questioning previous age assignments from the Boreal Realm solely based on planktonic foraminifera. Due to both moderately well-preserved microfossils and high sedimentation rates, the drilled succession of Anderten is considered as a potential Boreal reference section for the Albian-Cenomanian transition.

The Albian to Turonian carbon isotope record from the Shilaif Basin (United Arab Emirates) and its regional and intercontinental correlation

“…The latest Albian OAE 1d is associated with distinct black shale deposits in basins adjacent to the Neotethys and in cores from the Pacific and Atlantic Oceans (e.g. Gale et al ., ; Wilson & Norris, ; Bornemann et al ., , ; Gambacorta et al ., ; Giorgioni et al ., ; Navarro‐Ramirez et al ., ) and coincides with a ca 1‰ positive CIE. The Middle Cenomanian Event I (MCE I), a short‐lived, <1‰ positive δ 13 C CIE, has been reported from both the Boreal and Tethyan sections in North America, Europe, Arabia and Asia (e.g.…”

Aptian–Albian shale oil unconventional system as registration of Cretaceous oceanic anoxic sub-events in the southern Tethys (Bir M’Cherga basin, Tunisia)

“…In the rest of the basin, where more rich-marl facies dominated, the organic contents are moderate (about 1-2 wt% for TOC). This sub-event is well documented in Northern Thethys (Bornemann et al 2017), Southern part of the Atlantic, Indian Ocean and in Eastern part of Pacific Ocean (Bréhéret 1994;Erbacher et al 1996;Wilson and Norris 2001).…”

“…The third sub-event (OAE1c) of basal Upper Albian is indicated by Biticinella breggiensis biozone, and has been identified in central Italy, in inner western USA and in Australia (Bralower et al 1994;Coccioni and Galeotti 1993;Haig and Lynch 1993;Erbacher et al 1996). Finally, the sub-event OAE1d is of latest Upper Albian with Rotalipora appenninica biozone and is widely represented across the Tethys Ocean but sporadically represented in the southern part of the Atlantic and Indian Ocean and the eastern part of the Pacific ocean (Bréhéret 1994;Erbacher et al 1996;Wilson and Norris 2001;Bornemann et al 2017).…”

Mesozoic climates and oceans – a tribute to Hugh Jenkyns and Helmut Weissert

“…Consequently, the sedimentological and geochemical expression of individual OAEs can be quite different depending on local conditions (e.g. Bornemann et al ., ; Müller et al ., ).…”