A new extended record of Lower to lower Upper Aptian deposits in Northern Germany – new insights in the Boreal Oceanic Anoxic Event 1a

A recently cored 49-m-thick succession of Early to early Late Aptian age from Garbsen, a small city 6 km northwest of Hannover, has been studied with respect to sedimentology, bulk organic geochemistry and biostratigraphy.

The basal 14 m cover an alternating paper shale-mudstone sequence (topmost Hoheneggelsen Formation) with a 2.3-m-thick “Fischschiefer” bed at the top. It is overlain by partly reddish-colored hemipelagic marlstones representing lithostratigraphically the Sarstedt Member, formerly also named Hedbergella Marls. The “Fischschiefer” is considered to represent the local expression of the global Oceanic Anoxic Event 1a in the Lower Saxony Basin. During Early Cretaceous times the Hannover area represented paleogeographically the eastern-central part and, thus, the depocenter of the Lower Saxony Basin.

In addition to detailed lithological data, we present high-resolution δ¹³C_org, CaCO₃ and TOC data as well as a calcareous nannofossil biostratigraphy for this Boreal Aptian succession. This new core complements other records in the western part of the basin (Alstätte, Bottini et al., 2012) as well as southeast of Hannover (Hoheneggelsen KB9, Heldt et al., 2012) and, due to its completeness, provides new insights in the transition from the “Fischschiefer” deposit to the hemipelagic marlstone sedimentation.

 

References:

Bottini, C., Mutterlose, J., 2012. Integrated stratigraphy of Early Aptian black shales in the Boreal Realm: calcareous nannofossil and stable isotope evidence for global and regional processes. Newsl Stratigr 45, 115–137. doi:10.1127/0078-0421/2012/0017

Heldt, M., Mutterlose, J., Berner, U., Erbacher, J., 2012. First high-resolution δ¹³C-records across black shales of the Early Aptian Oceanic Anoxic Event 1a within the mid-latitudes of northwest Europe (Germany, Lower Saxony Basin). Newsl Stratigr 45, 151–169. doi:10.1127/0078-0421/2012/0019