Late Miocene increase in sediment accommodation rates in the southern North Sea Basin

Boreholes provided with biostratigraphic data indicate major changes in the Miocene sediment accommodation rates in the northern Campine Block, located in the southern North Sea Basin. Low sediment accommodation rates took place during the early to middle Miocene and abruptly increased into the late Miocene. Two processes likely explain these observations. First, the long-time (+/- 10 Myr) slow sedimentation of fine sands with a high-in part authigenic-glauconite content (of up to almost 50%) suggests that the southern North Sea area was sediment starved during the early to middle Miocene. Sediment starvation ended with the start of the late Miocene when the area became covered by west-prograding clinoform sets of coarser sands with mainly reworked glauconite as part of the proto-Rhine system. The latter sands filled the accommodation space that was left after early to middle Miocene sediment starvation. Second, accelerated subsidence during the late Miocene created additional accommodation space to be filled compared with the early to middle Miocene. A mechanism that explains well the regional accelerated subsidence is lithospheric folding or buckling. The timing and geometry of accelerated rates of subsidence in the southern North Sea area are indeed consistent with deformation that was thought to have been related to lithospheric folding in areas further south (in the direction of the Alps) under NW-Alpine compression.