Stratigraphic Chart - 1
Nomenclature for Cenozoic rocks of northeast Mogollon Datil volcanic field, New Mexico

by G. R. Osburn and C. E. Chapin, 1983, 7 p., 1 sheet (double sided).

A sequence of lithologically distinct, rock-stratigraphic units has been delineated in the Socorro-Magdalena-Datil area of the Mogollon-Datil volcanic field during the past 12 yrs. Informal names were used for most of these units while the mapping was in progress. Most of the area has now been mapped at 1:24,000 or larger, and the stratigraphic relationships are well established. Therefore, descriptions of the units and formalization of the nomenclature are now presented in Stratigraphic Chart 1. Previously used stratigraphic names have been retained where possible; however, several existing names were abandoned because they had been used elsewhere, or because multiple names existed for the same stratigraphic unit, or because, as mapping progressed from reconnaissance to detailed coverage, particular units became untenable stratigraphically. Obsolete units are listed in the glossary, and the reasons for abandonment are stated.

This chart has been prepared as a concise summary so that the essential information on all stratigraphic units will be available in one place. The front of the sheet presents general supportive figures including location maps, an index to mapping, and stratigraphic columns describing currently accepted stratigraphic units. These stratigraphic columns are organized into three sections: the Santa Fe Group and interbedded volcanic rocks, outflow volcanic units, and cauldron-related rocks. On the reverse side of the sheet are a glossary listing both current and obsolete nomenclature, a correlation diagram illustrating the chronologic development of the nomenclature, and a reference list; more detailed descriptions of type sections or type areas for those units being formalized are enclosed separately. The chart will be followed by a series of circulars examining the major stratigraphic units and a series of 7 1/2-min quadrangles using the standardized nomenclature.