Recovering the Linkage History of Large Faults from the Sediments of the Gulf of California Extensional Province

Analysis of the stratigraphy of sedimentary basins bounded by normal faults yield a wealth of information about how these brittle structures evolve through time forming array systems. However, mostly due to large uncertainties in the dating of sediments, little can be said about slip rates and how slip is accommodated during the interaction and linkage of normal faults. Cyclicity in sediments induced by Milankovitch climatic changes can be used as a very precise high-resolution stratigraphic chronometer, eliminating the problem of uncertainties in the dating. Therefore, the slip history of faults can be inferred with high accuracy. Here we present a cyclicity analysis of gamma-ray log from a borehole drilled in the Laguna Salada basin, a transtensional basin located in the Gulf of California extensional province. This has allowed us to establish its chronostratigraphy with a resolution of 50 kyr, from which the subsidence history of the Laguna Salada fault and its interaction with neighboring faults is recovered. We find that the long-term subsidence rate of the Laguna Salada basin has remained constant during the last 1.65 Ma (~1.4 mm/yr) in agreement with observations documented by other authors. However, our analysis reveals that at shorter timescales the subsidence history is composed of pulses lasting on average ~500 kyr. Subsidence rates during these pulses can vary by a factor of two with respect to the long-term subsidence rate. These pulses correlate with the breaking of the Laguna Salada Fault and the breaking of the Canon Rojo fault, a releasing stepover that links the Laguna Salada fault with the Canada David detachment to the south.