Taxonomy and quantitative biochronology of Guadalupian brachiopods from the Khuff Formation, Southeastern Oman

The Guadalupian Khuff Formation of the Huqf area (Sultanate of Oman) is composed of marine marls and bioclastic limestones which yield a rich brachiopod fauna associated with conodonts, foraminifers, ostracods, bivalves, gastropods, and cephalopods. The brachiopod fauna of the Khuff Fm. includes Perigeyerella raffaellae nov. sp., Derbyia sp. cf. D. diversa REED, 1944, Neochonetes (Sommeriella) arabicus (HUDSON & SUDBURY, 1959), Celebetes manarollai nov. sp., Haydenella sp., Chonetellini ? gen, and sp. indet., Dyschrestia rugosa nov. sp., Kozlowskia tescorum (HUDSON & SUDBURY, 1959), Calliprotonia sp., Juresania omanensis HUDSON & SUDBURY, 1959, Bilotina yanagidai nov. sp., Linoproductus sp. aff. L. kaseti GRANT, 1976, Grandaurispina ghabaensis nov. sp., Magniplicatina sp., Cyclacantharia sp., Acritosia sp., Orthotichia sp, cf. O. bistriata REED, 1944, Cleiothyridina sp. cf C. seriata GRANT, 1976, Pennospiriferinoidea genus and species undetermined, Dielasma sp. A, Dielasma sp. B, Dielasma sp. C, D. sp. aff. D. minor WAAGEN, 1882 and Hemiptychina sp. This fauna shows strong affinities with that of the Amb Fm. (Salt Range, Pakistan) and that of the Rat Buri Limenstone of southern Thailand. Analysis of the brachiopod data of the Khuff Fm by means of the Unitary Association method (Guex 1991) leads to the construction of a local biochronological sequence of eight faunal associations. Strictly based on a bed rock-controlled sampling, this result provides a firm basis and a first step for future correlations with other Guadalupian brachiopod sequences. It also suggests that species diversity and rates of faunal turnovers are only partly controlled by the vertical succession of depositional environments, which reflects an intra-Khuff asymmetric transgressive-regressive cycle. A full evaluation of the biochronologic component of the Guadalupian brachiopod faunas still requires further tests against other similarly well-documented sequences.