Planktonic foraminiferal biostratigraphy and paleomagnetic stratigraphy of late Cenozoic cores of the North Pacific suggest that the major polar planktonic foraminiferal invasions in southern California occurred in the last 800,000 years. In the Baldwin Hills of the Los Angeles basin, relations of the base of these polar planktonic assemblages and probable water depths at that time, on the basis of associated benthic assemblages, indicate an average rate of uplift of about 0.075 m/100 years.

On the basis of relation of radiocarbon dates with environments of deposition for the late Cenozoic, rates of uplift have increased to about 0.63 m/100 years for the past 36,000 years. Marine waters, approximately 100 m in depth 36,000 years ago, gave way gradually, through sedimentation and uplift, to nonmarine deposition in this area of the basin about 28,000 years ago. These early nonmarine deposits have been uplifted since then to elevations of 145 m atop the Baldwin Hills. Localized uplifts along the Newport-Inglewood fault trend may have formed recently, representing actively rising modern structural features along this trend in the Los Angeles basin.

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