The seismic analysis of the sedimentary infill of the Elkhorn Slough, central California, reveals a succession of three main seismic units: U1, U2, U3, with their correspondent discontinuities d2, d3. These units are deposited over a paleorelief representing the channel location at least 8k years ago. The location of that paleochannel has not changed with time, but the geometry of the infilling sedimentary packages has done so through the years. Discontinuities d2 and d3 show a relic island or relative high in the center of the Slough that separated the sedimentation into two main small basins at least 3k years ago. There is evidence of erosion in the last two sedimentary units showing that the present erosive pattern began decades ago at minimum. We have correlated radiocarbon data of selected cores with the high resolution chirp profiles and reconstructed the infill for the Elkhorn Slough.In the most recent unit, the occurrence of numerous lateral accretion surfaces on both ends of the main channel is discussed within their environmental setting, tidal currents and the net ebb flux of the area. We have interpreted the presence of gas in the sediments of the slough, with a gas front located at the tops of units 2 and 3, which are discontinuities that reflect an effective seal for the gas. Our data shows no obvious evidence for seepage, although the shallow presence of some of the fronts points out the fragility of the environment in the present erosive conditions.
Bibliographical noteFunding Information:
The authors wish to thank the SeaFloor Mapping Lab at CSUMB for use of their Edgetech CHIRP profiler, Captain Ron Eby for his time and skillful handling of the acquisition vessel, Geoff Shipton of Triton Imaging for his assistance during acquisition and interpretation of CHIRP data, and Triton Imaging for donating their excellent seismic acquisition and interpretation software. We also wish to thank the staff of the Elkhorn Slough Foundation for their assistance and use of equipment. We would like to also thank the reviewers Mr. Maher and editor Mr. Jonathan Sharples, whose suggestions and comments improved the earlier version of the manuscript. Funding and support for this project was provided by CICEET, the Cooperative Institute for Coastal and Estuarine Environmental Technology. A partnership of the National Oceanic and Atmospheric Administration and the University of New Hampshire, CICEET develops tools for clean water and healthy coasts nationwide. Partial support was also provided by Fugro Geoconsulting Inc. We want to thank Dr. Gary Hampsom for his insight regarding lateral accretion surfaces and point and counter point bars, and Dr. Gary Greene for clarification on the geological background. We also thank Dr. Ivano Aiello at Moss Landing Marine Laboratories for early discussions on the manuscript.
Copyright 2013 Elsevier B.V., All rights reserved.
- Elkhorn Slough
- High-resolution seismic analysis
- Marine transgression
Continental Scientific Drilling Facility tags