Chitinozoan biostratigraphy of the Late Devonian formations in well Caima PH-2, Tapajós River area, Amazonas Basin, northern Brazil

Abstract

The chitinozoan biostratigraphy of the Barreirinha Formation in its type area (Tapajós River near Itaituba town, Pará State, Amazonas Basin, north Brazil), and of the lower part of the overlying Curiri Formation, is calibrated against the local miospore succession, which in turn can be readily correlated with standard miospore biozonations of Euramerica. The present study is based on 375 samples from a ca. 137-m-thick section in the Caima PH-2 shallow borehole. The 26 chitinozoan species encountered are used to recognize eight biozones in the studied well. The applicability of this zonation is yet to be tested elsewhere in the Amazonas Basin. The zones in ascending stratigraphic order are: the total range zone of Angochitina katzeri n. sp., total range subzone of Ramochitina derbyi n. sp, total range subzone of Lagenochitina avelinoi, interval zone of Urochitina bastosi, total range zone of Angochitina carvalhoi n. sp., interval zone of Angochitina rathbuni n. sp. and Ramochitina praeritae n. sp., total range zone of Ramochitina ritae n. sp., and total range zone of Ramochitina cf. R. ritae. Eleven species are newly described; in order of stratigraphic appearance: Ramochitina derbyi, Angochitina katzeri, Ramochitina hartti, Angochitina carvalhoi, Angochitina rathbuni, Ramochitina praeritae, Ramochitina clarkei, Ramochitina ritae, Angochitina loboziaki, Ramochitina oliveirai, and Ramochitina famennense.