Evidence in the Rocks (IMAGE) University of Oregon Caption Bioclastic limestone and cross-bedded conglomerate are visible in exposed rocks at Marl Wash in the Bouse Formation, south of Blythe, California. The wash was named by geologists studying the deposits. The sedimentary structures preserve a record of deposition by strong tidal currents at the north end of the Gulf of California about 6 million years ago, prior to arrival of the Colorado River and its sediment load. A team led by University of Oregon geologist Rebecca Dorsey interpreted a wide range of depositional processes and environments, and their changes through time, using detailed stratigraphic analysis and micropaleontology. Credit Photo by Rebecca Dorsey Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.