USGS Quadrangle Map (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption On USGS quadrangle maps from 1947-1992, oil wells are marked by hollow black circles. Credit Historical Topographic Map Collection/USGS Usage Restrictions N/A License Original 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.