Differentiating between tectonics and eustatic controls in coarse-grained, syn-rift sedimentary basins: Baja California Sur, Mexico

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Depositional architectures of syn-rift deltas are controlled by tectonic, eustatic, and sediment supply (climatic) variations. Most often, they are considered result from short-term eustatic variations superimposed on long-term tectonic fluctuations. The San Jose transtensional basin is one of several that form the western margin of the Gulf (of California) Extensional Province (GEP). It contains exceptionally exposed sediments deposited during the early evolution of the Gulf (3-4 Ma), providing one of the earliest records of sedimentation associated with the modern configuration of the Gulf. Existing studies in the contemporary Loreto basin, GEP, recognise stacked coarse-grained deltas, and suggest that their architecture is controlled by episodic accelerations in the rate of tectonically-controlled subsidence, rather than eustatic cyclicity. A multidisciplinary analysis in the San Jose basin would test this hypothesis, and provide a characterisation of depositional architectures to discriminate between tectonic and eustatic controls that could be applied to other rifts. It would also provide important constraints on strain distribution contributing greatly to our understanding of strain localisation during the northward propagation of the Gulf.