New Mexico Geological Society Annual Spring Meeting — Abstracts

Located in the Manzanita Mountains of central New Mexico, the Kinney Brick quarry is a world famous Late Pennsylvanian fossil locality in an estuarine deposit. The quarry is located in the Atrasado Formation (locally designated the “Wild Cow Formation” in previous studies), a regionally extensive stratigraphic unit of well-established Late Pennsylvanian age, based on fusulinid biostratigraphy. However, the precise age of the Kinney quarry deposit has been difficult to determine because virtually all of the fossils from the quarry are not precise age indicators. Thus, the age assigned to the Kinney quarry (middle Virgilian) has long been based more on its inferred lithostratigraphic position than on biostratigraphic indicators at the quarry. This age assignment has relied on USGS geologic mapping (especially USGS Map I-968), which located the Kinney quarry stratigraphically high in Myers’ (1973, USGS Bulletin 1372-F) “Pine Shadow Member” of the Wild Cow Formation, a local map unit that fusulinid biostratigraphy (in other parts of the mountain range) indicates is of middle Virgilian age. In contrast, we have developed three datasets that indicate the Kinney quarry is older---stratigraphic position, fusulinids and conodonts. Our detailed local lithostratigraphic studies coupled with regional stratigraphic investigations indicate the Kinney quarry is in the Tinajas Member of the Atrasado Formation, so it is stratigraphically lower (i.e., very near the base of Myers’ “Pine Shadow Member”) than suggested by previously published maps. A laterally extensive fusulinid-bearing limestone a few meters below the level of the Kinney quarry yields an early-middle Missourian fusulinid assemblage consisting of Tumulotriticites cf. T. tumidus and species of Triticites: T. cf. T. planus, T. cf. T. myersi and T. ex gr. T. ohioensis. Conodonts from the basal beds of the Kinney quarry are also Missourian species, though they indicate an age slightly younger than do the fusulinids. Thus, the Kinney conodont fauna is dominated by members of the Idiognathodus symmetricus - I. multinodosus group, species of which appear in the middle Missourian and range into the Virgilian (middle Kasimovian into the base of the Gzhelian).We conclude that the Kinney quarry Lagerstätte is of Missourian age, most likely middle Missourian