Figure 1. Index map and cross section of San Juan Basin. Outcrops of Ojo Alamo Sandstone and Animas Formation modified from Fassett and Hinds (1971, plate 1). 1.1 Important fossil localities and paleomagnetic-section localities through parts of Ojo Alamo Sandstone and adjacent strata. Isopach map shows thickness of interval between Huerfanito Bentonite Bed and base of Ojo Alamo Sandstone. Area between Hunter Wash and De-na-zin Arroyo is type area for Ojo Alamo Sandstone. D4119, D5393, D5394, D5408, D6877, and MM are USGS paleobotany localities. DA (Durango area) palynologic site from Newman (1997). Bone symbol labeled FSS shows locality of dinosaur-bone sample collected for chemical analysis. 1.2 Stratigraphic cross section A-A' showing interval from Huerfanito Bentonite Bed to base of Ojo Alamo Sandstone. Wells shown on cross section listed in Fassett and Hinds (1971). Modified from Fassett et al. (2002).