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The Paleobiology Database is an online, non-governmental, non-profit public resource for paleontological data. It is organized and operated by a multi-disciplinary, multi-institutional, international group of paleobiological researchers. This volume is designed to be a comprehensive guide for Pa-leobiology Database users, both General and Contributory. It covers most database uses from data retrieval and mapping to data contribution of all types. It contains numerous examples to illustrate database use as well as definitions of terms and additional links to numerous other sources. We hope that this user guide will help all users access the great volume of data in the Paleobiology Database and lead others to start and continue to add data to the system. 

Abstract The San Diego Formation, Pico Formation, Careaga Sandstone, and Foxen Mudstone of southern California are thought to be late Pliocene to early Pleistocene; however, numerical ages have not been determined. Following assessment of diagenetic alteration via multiple methods including scanning electron microscopy (SEM), X-ray diffraction (XRD), and minor elemental concentrations, we attempted to use strontium isotope stratigraphy to assign numerical ages. Using aragonitic fossils, we obtained ages of 2.0–1.85 Ma for the Careaga Sandstone and 2.0–1.75 Ma for the uppermost Foxen Mudstone, consistent with biostratigraphic work suggesting a Gelasian age for the Careaga Sandstone. Isotope ratios for aragonitic and calcitic fossils from the Pico Formation were poorly constrained, with the exception of one bed yielding ages of 5.1–4.3 Ma. Isotope ratios from the San Diego Formation were also inconsistent within beds, with the exception of two isolated outcrops that yielded ages of 5.0–4.5 Ma and 4.5–2.8 Ma, respectively. The age estimates for the Pico and San Diego Formations are older than most ages inferred from biostratigraphy. Noting that some aragonitic specimens from the San Diego Formation yielded isotope ratios indicative of ages as old as 19.4 Ma, we propose that some outcrops have been affected by diagenesis caused by groundwater flow through proximal granitic rocks and input from detrital sediment. Although we recommend that strontium isotope results for the Pico and San Diego Formations be interpreted with caution, the ages of the uppermost Foxen Mudstone and Careaga Sandstone can be confidently placed within the early Pleistocene.