Contributions Series Nr. 47

Description

Abstract

Mississippian (Lower Carboniferous) sequences penetrated by numerous hydrocarbon-exploratory wells in the Amazonas Basin, northern Brazil, contain an abundance and diversity of plant microfossils that are readily applicable to biostratigraphic analysis, and hence to detailed correlation and age determination of the host strata. This study, presented in two successive parts, comprises a detailed systematic-descriptive survey of miospore assemblages preserved in core samples from selected boreholes that intersected and are well representative of the Mississippian portion of the Oriximiná Formation and of the partly overlying, partly laterally equivalent Faro Formation. In the current Part One, representatives of trilete miospore taxa featuring relatively simple morphology (i.e., with acavate/azonate exines, variously sculptured) are described and illustrated. Part Two completes
the systematic analysis of the miospores and details their stratigraphic significance, re-assessing and augmenting
a palynozonal scheme established previously (in 2003).

In this part, 70 species and species groups within the above-stated morpho-taxonomic category are described and illustrated. They are attributable to 25 genera, one of which – Claytonispora – is established as a new genus of trilete, distinctively apiculate, acavate miospores. Four new species are proposed: Leiotriletes pachytunicus, Verrucosisporites gregatus, Anapiculatisporites semicuspidatus, and Apiculatasporites quadrosii. Additionally, five new combinations are established: Claytonispora distincta (Clayton, 1971), Claytonispora rarisetosa (Kedo, 1963), Corbulispora cancellata (Waltz in Luber & Waltz, 1938), Cordylosporites absimilis (Daemon, 1974), and Cordylosporites glumaceus (Byvsheva, 1972). The majority of the species are identifiable with species described and named previously from Mississippian palynofloras of Western and Eastern Gondwana and, in the case of cosmopolitan or near cosmopolitan forms, also from Euramerican regions.

Key words: Miospores, systematic palynology, Amazonas Basin, Mississippian (Lower Carboniferous), Brazil