Paleocene Strata of the Basque Country, Western Pyrenees, Northern Spain: Facies and Sequence Development in a Deep-Water Starved Basin (original) (raw)

Mesozoic and Cenozoic Sequence Stratigraphy of European Basins, 1998

Abstract

Paleocene sediments are not thick in the Spanish Basque Country (usually less than 200 m), largely composed of stacks of hemipelagic limestones and marls deposited in a clastic-starved deep basin. In addition to these, resedimented carbonates accumulated on base-of-slope aprons girding the basin, and resedimented carbonates plus lesser amounts of coarse-grained siliciclastics discontinuously plugged a deep-sea channel system incised on the basin floor. Third-order depositional sequences that attest to sea-level changes have earlier been recognized in the apron and channel systems (Pujalte et al., 1993). Further analyses have now demonstrated that these sea-level changes are also expressed in the hemipelagic sections by means of basin- wide variations in sedimentation rates through time, relative proportions of limestones and marls and, locally, the type of turbidite intercalations. The building blocks of these sequences are high-order stratification cycles, probably tuned to Milankovitch frequencies. Since these hemipelagic sections contain a nearly continuous stratigraphic record, a reliable reconstruction of the Paleocene sea-level changes that affected the Basque basin has been possible. A good match has been found between the regional sea-level curve derived from the deep-sea record and that of the global chart of Haq et al. (1988), mainly based on coastal onlap. This correlation clearly demonstrates that the signature of sea-level changes can be confidently unravelled from deep-marine successions, though it remains to be seen whether it reflects an eustatic signature or a bias of the data base.

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