LATE WORDIAN (GUADALUPIAN, MIDDLE PERMIAN) RADIOLARIANS FROM THE APACHE MOUNTAINS, WEST TEXAS, USA

Several continuous sections (named BWK, B, A, G, K, EF, M and Z) of Wordian and Capitanian (Middle Permian) strata are exposed in a series of road cuts along TX FM Road 2185 about 50 km northeast of Van Horn in the structurally complicated northwestern part of the Apache Mountains, Delaware basin in West Texas. The oldest strata of these sections, the BWK section, is about 7 m thick and is located in a small gully on the south-eastern side of the road and stratigraphically under a several meter thick debris flow which forms the base of the B section, in the upper part of which the Wordian/Capitanian boundary is present based on the clines of conodonts Jinogondolella aserrata/J. postserrata. The BWK section consists of interbedded thin carbonate mudstone to packstone with limey siltstone intervals interrupted by several medium to thick beds of debris flows. The section is capped by the massive debris flow noted above that also marks approximately the base of strata analogous in age to the Pinery Limestone Member of the Bell Canyon Formation as exposed in the Guadalupe Mountains. Based on the presence of the conodont species Jinogondolella aserrata (Clark and Behnken) and Jinogondolella palmata Nestell and Wardlaw 2010 in the BWK section, the section has been interpreted by Nestell and Wardlaw as analogous in age to the Hegler Limestone Member of the Bell Canyon Formation. In the Hegler Limestone Member Nazarov and Ormiston established the Hegleria mammifera or Latentifistula texana radiolarian zone. The BWK section contains conodonts, ostracodes, foraminifers, ammonoids, fish remains and a rich assemblage of radiolarians represented by 44 species of 23 genera. The stratigraphically important species are: Follicucullus japonicus, Pseudoalbaillella scalprata, Ps. yanahanensis, Entactinia modesta, “Entactinosphaera” crassispinosa, Wuyia endocarpa, Hegleria mammifera, Octatormentum cornelli, Shangella capitanensis, Latentifistula texana, Tetragregnon japonicum, and Nazarovispongus delicatum. Many of these species occur at different Middle Permian stratigraphic levels in the Delaware basin, and also in coeval pelagic chert sequences of Japan and China. The presence of the species Hegleria mammifera and Latentifistula texana do not conflict with the correlation the BWK section strata to the Hegler Limestone Member.