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Sedimentological and ichnological facies analysis of the terrestrial to nearshore deposits of the Bückeberg Group, Lower Saxony, Germany

The Bückeberg Group in the Lower Saxony Basin, northern Germany, records the transition from a lowstand systems tract to a transgressive systems tract during the Berriasium. The terrestrial to nearshore deposits of the Bückeberg Group comprise sandstone- and mudstone-dominated intervals. These sandstone-dominated intervals act aspotential geothermal reservoirs[GvG1] , especially where sandstone exceeds porosities and permeabilities of 30% and 500 mD, respectively. However, the sedimentological and ichnological character of reservoir facies, and their vertical and lateral distribution are complex and a sequence stratigraphic framework has yet to be established.

Facies and facies associations are identified by logging a set of 12 cores that bear terrestrial and nearshore deposits. Facies descriptions focus on sediment texture, sedimentary structures, lithological accessories, bioturbation index (BI), bioturbation distribution, and trace fossil assemblage. Vertical juxtaposition of facies associations are identified to delineate sequence stratigraphic surfaces. Three reservoir facies are identified and interpreted as (1) brackish-water, wave- and river-dominated deltaic deposits, (2) spit and barrier deposits, (3) fluvial channel and crevasse splay deposits. Several small-scale base level fluctuations took place during the overall transgression resulting in a complex distribution of reservoir facies.

The sedimentological and ichnological facies analysis of the Bückeberg Group permits refined reconstructions of its paleodepositional environments. Establishing a sequence stratigraphic framework offers valuable insight into the onset of Early Cretaceous transgression in the Lower Saxony Basin and enhances reservoir quality predictions.

Details

Author
Susanne W. Fietz1
Institutionen
1Federal Institute for Geosciences and Natural Resources, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/p9ne-nt41