GLOBAL CORRELATION POTENTIAL OF LINGULIFORM BRACHIOPODS FROM THE UPPER CAMBRIAN (SUNWAPTAN) HELLNMARIA MEMBER OF THE NOTCH PEAK FORMATION OF WESTERN UTAH
The Hellnmaria in northern Tule Valley is primarily lime mudstones deposited in a deep subtidal environment in the House Range Embayment. At East Shoreline Butte and Chalk Knolls North sections, bulk samples from these beds have yielded abundant linguliform brachiopods in insoluble residue. There is a complete turnover of brachiopod faunas from the base to the top of the Hellnmaria. Most of this turnover occurs between 200 and 450 feet (61-137 meters) above the base of the 1201-ft (366-m) thick combined section. Most brachiopod species originating in this interval have long ranges, ranging into the overlying Red Tops and Lava Dam Members of the Notch Peak Formation.
The lower beds of the Hellnmaria yield Zhanatella rotunda Koneva, 1986, a species found previously in Kazahkstan and the Montagne Noire area of France, suggesting that the lower Hellnmaria is coeval with the Kujandy Formation of northeastern central Kazahkstan, and the Val d’Homs Formation of southern France. The Montagne Noire region is interpreted to have been part of northwestern Gondwana during the Late Cambrian, and because neither locale was part of Laurentia, the occurrence of this brachiopod has potential for international correlation.
The occurrence of Zhanatella rotunda in the Hellnmaria also suggests that the House Range Embayment was an area of the Late Cambrian continental shelf that was deep enough to allow incursion of globally distributed species which may have been adapted to deeper offshore environments. Other linguliform brachiopods of the Hellnmaria are distributed globally at the generic level. Correlation within Laurentia is hampered by a lack of studies of linguliform brachiopods of this interval, although ongoing work on equivalent strata in Texas shows promise, with several species in common to both locales.