Journal of Paleontology; May 2007; v. 81; no. 3;
p. 581-587; DOI: 10.1666/04125.1
© 2007 Paleontological Society
NEW CARBONIFEROUS BRYOZOA OF THE BIRD SPRING FORMATION, SOUTHERN NEVADA
ERNEST H. GILMOUR1
1 Department of Geology, Eastern Washington University, Cheney, Washington 99004, <EGilmour@Mail.EWU.EDU>
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INTRODUCTION
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BRYOZOANS WERE collected from a thin shaley limestone in the lower part of the Bird Spring Formation in the northern part of the Muddy Mountains, Clark County, southern Nevada (Fig. 1). The purpose of this paper is to describe a new genus and two new species of these bryozoans. The fauna of the Bird Spring Formation has taken on a new importance with the formation's designation as the Global Boundary Stratotype Section and Point (GSSP) for the Mid-Carboniferous Boundary (Lane et al., 1999). Samples were collected from the bryozoan-bearing unit while teaching field camp during the spring of 1994.
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FIGURE 1—Index map showing location of sampling area in Muddy Mountains, Nevada
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The Carboniferous sequence in the Muddy Mountains consists of three formations in ascending order: the Battleship Wash Formation (Meramecian to early Chesterian: late Visean); Indian Springs Formation (late Chesterian: late Serpukhovian); and Bird Spring Formation (late Chesterian to Wolfcampian: Sakmurian) (Lane et al., 1999).
The age of the Bird Spring Formation has been reported to be late Chesterian (Serpukhovian) into Wolfcampian (Sakmurian) (Langenheim and Langenheim, 1965; Ross, 1997; Lane et al., 1999). Based on the conodonts collected from beds directly above and below the bryozoan-bearing beds in this study, the age of these bryozoans is middle to late Morrowan (Wardlaw, personal commun., 1999).
The Bird Spring Formation represents a cyclical unit deposited during the transgressions and regressions of the Pennsylvanian sea. The thin shaley limestone from which the bryozoans were collected has bioclastic wackestone beds above and below. These wackestone beds contain fragments of brachiopods, crinoids, echinoids, and bryozoans. The bioclastic wackestone and shaley limestone containing the bryozoans was probably deposited in normal marine water below wave base.
The Arrow Canyon Section of the Bird Spring . . . [Full Text of this Article]
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