Ordovician conodonts and ostracods from the Katkoyeh Formation at the Banestan Section, Kerman Province of East-Central Iran

POURSALEHI, FARZAD; VOLDMAN, GUSTAVO; SALAS, MARIA JOSE; AMERI, HAMED

Jornada; 2nd Annual Meeting of IGCP 735 (Filling knowledge gaps in the Early Paleozoic Biodiversification and Promoting Geological Heritage); 2022

International Geoscience Programme (IGCP) UNESCO

Ordovician marine sedimentary sequences deposited in several widely separated structural blocks in Iran, along the northern margin of Gondwana. Parts of the sequences contain rich fossil faunas, such as conodonts, trilobites or brachiopods, but with a small number of notable exceptions, there are few studies on the taxonomy, biostratigraphy or biogeography of these biotas. In the Kerman Province to the south of Tabas, the Ordovician sedimentary interval is known as the Katkoyeh Formation, which encompasses a ⁓70-300 m column of siliciclastic rocks with scarce carbonate beds and pyroclastics in its upper part. Few studies have focused on its fossil content, generally supported by the relative dating of conodont or graptolite spot samples. These provided variable ages ranging from the Tremadocian up to Hirnantian, and indicating the presence of regionally important stratigraphic gaps. In order to enhance the conodont biostratigraphy of the Katkoyeh Formation, new conodont samples were obtained from the Banestan Section, located about 12 km northwest of the city of Zarand, in the vicinity of the Banestan Village, in northern Kerman Province. There the Katkoyeh Formation consists of ⁓150 m of silty shales, diabase, pillow lava, basaltic tuff, red sandstone, red silty claystone, marl, limestone and sandy limestone. It rests above the upper dolomites of the Kuh-Banan Formation and is in turn overlain by the Niur Formation, a lateral stratigraphic equivalent to the Shabdjereh Formation. Based on the occurrence of important biostratigraphic species, we determined three conodont intervals in ascending order in the Katkoyeh Formation, namely the 1) Rossodus manitouensis/Paltodus deltifer Zone (middle Tremadocian, Lower Ordovician), characterised by the indexes species along with Acanthodus lineatus (Furnish), A. uncinatus Furnish, Cordylodus angulatus Pander, C. caseyi Druce & Jones, Drepanoistodus sp. and Paroistodus sp. This faunal association allows for a correlation with the Derenjal Mountains of Central Iran (Shirgesht Formation). It also provides a tight intercontinental correlation with the Rossodus manitouensis and Paltodus deltifer zones of Laurentia, Baltica, China, Kazakhstan, Korea, Thailand, and the southern South American margin of Gondwana (e.g., Central Andean Basin and the Argentine Precordillera). The overlying conodont samples yielded 2) a Floian (Lower Ordovician) assemblage, characterised by Bergstroemognathus extensus (Graves & Ellison) and Reutterodus andinus Serpagli; and 3) a Late Ordovician assemblage, which is supported by the co-occurrence of Icriodella superba Rhodes and “Sagittodontina” sp. The latter assemblage is accompanied by two new species of ostracods: Satiellina n. sp. and Ceratopsis n. sp., both suggest paleobiogeographical affinities mainly with Gondwana and peri-Gondwana. The fauna discussed herein was obtained by two of us (A. Bahrami and P. Farzad), and makes up part of a larger PhD project at the University of Isfahan, providing new significant information on the biostratigraphy and intercontinental correlation of the Ordovician faunas of East-Central Iran