Early Ordovician (Bendigonian) conodonts from central New South Wales, Australia

Contents

Abstract

The first Early Ordovician conodont fauna recorded from central New South Wales, comprising 16 species (belonging to 14 genera), is described and illustrated. The fauna occurs in laminated calcareous siltstones and allochthonous limestones of the Hensleigh Siltstone, south of Wellington. Both lithologies are interpreted as having been deposited in a lower slope graptolitic siltstone facies. Worldwide correlation of this conodont fauna points to an age equivalent to the upper P. elegans Zone of the North Atlantic succession or O. communis Zone of the North American Midcontinental succession, according well with the late Bendigonian age determined from graptolites in overlying beds of the Hensleigh Siltstone. Juanognathus variabilis (32% of total elements), Acodus comptus (19%), Bergstroemognathus extensus (14%) Drepanodus arcuatus (7%), Reutterodus andinus (6%) and Acodus sweeti (6%) dominate the assemblage, which is comprised of cosmopolitan, as well as so-called “cooler water”, species; with one exception, typical shallow “warm water” forms are lacking. Beyond the Australian region of low-latitude, East Gondwana, the New South Wales fauna is most closely correlated with faunas from the Argentinian Precordillera and South China. Strong similarities also are apparent between the Hensleigh conodont assemblage and deeper water, low-latitude faunas from platform margin or slope settings of eastern North America, as well as those from the western margins of the North China block. The Hensleigh conodont fauna represents a deeper water assemblage that formed on the west side of the Palaeo-Pacific Ocean, beyond the margin of East Gondwana.

 
Early Ordovician (Bendigonian) conodonts from central New South Wales, Australia