HOLOCENE RELATIVE SEA LEVEL HISTORY FOR CENTRAL AND SOUTHERN CALIFORNIA

A geographically diverse distribution of Holocene relative sea-level data is important for constraining glacial isostatic adjustment models and providing datums for measuring recent tectonic rates. However, few records of Holocene relative sea levels exist for the Pacific coast of North America south of San Francisco Bay. We present two Holocene relative sea-level curves for California: one for southern California developed from 85 previously published radiocarbon dates from 11 estuaries south of Point Conception, and a second from central California developed from 45 dates from Elkhorn Slough in Monterey County. We corrected the data to a consistent datum (depth below mean sea level), and accounted for long term uplift and geographically variable radiocarbon reservoir. The sea-level trajectory for southern California is similar to that from other intermediate-field locations, including San Francisco Bay—a steep (~10m/ky) rise from 9-7 ka followed by deceleration to around 1m/ky since 7 ka. In contrast, Elkhorn Slough shows a near linear ~2.9m/ky sea-level rise over the last 7 ky. The differences in sea-level histories between Elkhorn Slough and San Francisco Bay indicate 1.4 to 1.8m/ky of tectonic or compaction-related subsidence in Elkhorn Slough. This study provides the first regional Holocene relative sea-level curve for southern California and demonstrates its utility in identifying deviations due to local processes.