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Combining Sequence Stratigraphy and Growth Stratigraphy to Assess the Tectonic Evolution of the Los Angeles Basin


The Los Angeles basin is one of the most studied basins in the world due to the incredible quantity of hydrocarbons it has produced per sediment volume and the high seismic hazard in the region. Nevertheless, a detailed understanding of the spatial and temporal evolution of the many structures within the basin has remained elusive. Our study is focused on defining the growth history for the Puente Hills thrust fault system (PHT) and Compton thrust fault. The basin is filled with syntectonic growth stratigraphy deposited onto growing folds above both strike-slip and thrust fault systems. Identifying and mapping time-correlative stratigraphic markers, however, has been a great challenge for researchers due to the time-transgressive nature of the faunal assemblages traditionally used to constrain stratigraphy from regional wells. To overcome this, we utilize the sequence stratigraphic model and well picks of Ponti et al. (2007) as a basis for mapping roughly time-correlative sequence boundaries from the present into the Pleistocene throughout our depth-converted 2-D industry seismic reflection dataset. We identify additional sequence boundaries into the Pliocene from imaged sequence geometries, and correlate industry well formation tops down to the Miocene. The sequence boundaries are used to build three-dimensional surfaces in the modeling program GOCAD. From these surfaces we infer fold geometries at the time of each sequence deposition. Along with published age constraints for Quaternary sea level change, we also determine uplift rates between many of the sequences. Our results show three distinct phases of deformation on the PHT. The earliest phase was characterized by fault-propagation or structural wedge kinematics that terminates in the early Pleistocene, followed by a period of quiescence. The faults were reactivated in the middle Pleistocene and propagated upward to detachments, with the deformation characterized by fault-bend folding kinematics. Slip on the westernmost segment of the PHT decreases westward, suggesting lateral growth in that direction. The Compton structure also experienced quiescence contemporaneous with the PHT, followed by fault-bend folding kinematics. Growth-stratigraphy below the quiescent interval shows a combination of limb-rotation and kink-band migration kinematics. Our work highlights how elements of sequence stratigraphy and structural Geology can be used together to constrain past fold geometries and deformation rates.