The interplay between siliciclastic and carbonate depositional systems: Maastrichtian to Danian basin-floor sediments of the mid-Norwegian More Basin

Source-to-sink sedimentary systems associated with volcanic rifted margins serve as important archives for basin development by recording lithospheric changes affecting the depositional systems. Distinguishing between sediment transport processes and their sediment source(s) can guide the interpretation of a basin's history, and thereby inform regional paleogeographic reconstructions. In this contribution, we integrate and utilize wireline geophysical logs, detailed petrographic observations from side-wall cores, and seismic analysis to describe and decipher a Maastrichtian to Danian-aged basin-floor depositional system in the deep outer More Basin, mid-Norwegian margin. Well 6302/6-1 (Tulipan) is a spatially isolated borehole drilled in 2001 that penetrates Maastrichtian and younger strata. A succession of hitherto undescribed carbonates and sandstones in the outer More Basin was discovered. It is investigated for sediment transport, provenance, and depositional processes on the basin floor surrounded by structural highs and ridges. The strata from the lower parts form a basin-floor apron consisting of redeposited carbonate sourced from a westerly sub-aerial high. The apron transitions vertically from mixed siliciclastic and carbonate into a purely siliciclastic fan with intercalated sandstone and mudstone, providing a rare high-resolution record of how depositional environments experience a complete shift in dominant processes. The development coincides with similar latest Cretaceous-earliest Palaeocene sequences recorded south of this region (e.g., well 219/20-1) and may have been influenced by regional uplift associated with the onset of magmatism in the Northeast Atlantic. This study improves our understanding of a late, pre-breakup source-to-sink sedimentary system developed near the breakup axis of an infant ocean, and documents what is possibly the northernmost chalk deposit in the Chalk Group.

Automated summary

This study describes and deciphers a late Maastrichtian to Danian-aged basin-floor depositional system in the deep outer More Basin, mid-Norwegian margin. The study integrates and utilizes wireline geophysical logs, detailed petrographic observations from side-wall cores, and seismic analysis. The research provides insights into sediment transport, provenance, and depositional processes in a pre-breakup source-to-sink sedimentary system near an infant ocean's breakup axis.