Abstract

We propose a new technique, paleostress stratigraphic analysis, based on the orientation of minor structures, particularly striated fault surfaces, in the strata of sedimentary basins. These structures are interpreted to be the response to local or regional stress fields controlling subsidence of tectonically active basins. A method is used that allows multiple stress tensors to be extracted from a fault population. By extracting the stress tensor from the youngest part of a stratigraphic sequence and by imposing that same tensor on the underlying rocks, one can, in principle, isolate the faults associated with the youngest tectonic event. By reiterating this procedure on progressively older units until the fault data are exhausted, a chronologic succession of paleostress tensors during basin subsidence emerges.

We apply paleostress stratigraphy to the relatively undeformed Paleogene Central Basin of Spitsbergen and its underlying Cretaceous strata, and define five major paleostress tensors coeval with the earliest stages of the opening of the Norwegian-Greenland Sea. A Late Cretaceous dextral transpressive regime was probably responsible for the major pre-Tertiary unconformity and possibly initiated development of the Central Basin. During subsequent sedimentation, movement reversed, yielding well-constrained sinistral shearing during early Danian time. A composite compressional event followed that we interpret as being coeval with the culmination of folding and thrusting west of the Central Basin. The youngest strata studied record a final extensional event that we correlate with rifting of Spitsbergen from Greenland.

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