RECONSTRUCTING LATE PLEISTOCENE RSLS ON TRANSGRESSED SHELVES: AN EXAMPLE FROM CENTRAL CALIFORNIA

Although prevalent for the late Holocene, relative sea level (RSL) constraints during and immediately after the Last Glacial Maximum (LGM) are sparse. This scarcity of data is particularly pronounced along mid-latitude shelves such as central California, which lacks post LGM RSL constraints older than 12 ka. In this study we collected 8 sediment cores and high-resolution seismic data to constrain RSLs across the central California shelf between ~9 and ~18 ka. We reconstruct these RSLs using two sea-level indicators found within our sediment cores: the wave ravinement surface (WRS) and the sedimentary contact between offshore mud facies and hummocky cross-stratified sands. To determine the indicative meaning of these two sea-level indicators, we examine the relationship between the local wave regime and the depth of preservation of each sea-level indicator. After correcting for tectonic uplift, we estimate sea levels in central California to have been ~ 36 and 38 ± 5.5 m below present sea level between 10 - 11 ka, in agreement with previous RSL reconstructions along this coast. Between 15.3 and 18.0 ka, we estimate sea levels to have reached ~ 96 -103 ± 5.3 m below present sea level. Furthermore, we map the farthest offshore extent of the WRS, which provides a new estimate for the elevation of the LGM lowstand in central California at ~ 107 ± 5.4 m below present sea level. Our findings offer a Late Pleistocene RSL reconstruction for central California and develop new methodologies for estimating past RSLs on similar mid-latitude shelves.