major basement rock units for the LA Basin. Large-scale movement along the Newport–Inglewood zone juxtaposed the two bedrock units along the east and west margins. During this phase, the basin was above sea level. Phase 2: Pre-basin phase of deposition The hallmarks of this phase were successive shoreline transgression and regression cycles. Deposition of older marine and non-marine sediments began to fill the basin. Towards the end of this phase, the shoreline began to retreat and deposition continued. Phase 3: Basin inception After the deposition of the pre-Turonian units, there was a large emergence and erosion that can be observed as a major unconformity at the base of the middle Miocene units. Emergence did not occur at the same rate or in all sections of the basin. During this time, the basin was covered by a marine embayment. Rivers sourced in the highlands brought large amounts of detritus to the northeastern edge of the basin. During this period, the Topanga formation was also being deposited. Phase 4: Principal phase of subsidence and deposition The present form and structural relief of the basin was largely established during this phase of accelerated subsidence and deposition which occurred during the late Miocene and continued through the early Pleistocene. Clastic sedimentary rocks from the highland areas (to the north and east) moved down the submarine slopes and infilled the basin floor. Subsidence and sedimentation most likely began in the southern portion basin. Subsidence and Deposition occurred simultaneously, without interruption, until the late Pliocene. Until the rate of deposition gradually overtook the rate of subsidence, and the sea level began to fall. Towards the end of this phase, the margins of the basin began to rise above sea level. During the early Pleistocene, deposition began to outpace subsidence in the depressed parts of the basin and the shoreline began to move southward. This phase also had movement along the Newport–Inglewood fault zone that resulted in the initiation of the modern basin. This movement caused the southwestern block to be uplifted relative to the central basin block. Phase 5: Basin disruption The central part of the basin continued to experience sediment deposition through the Pleistocene from flooding and erosional debris from the surrounding mountains and Puente Hills. This infill was responsible for the final retreat of the shoreline from the basin. Deposition in the Holocene is characterized by non marine gravel, sand and silt. This phase