Callovian foraminiferal assemblages in West Siberia

Abstract

The paper presents data on Callovian foraminiferal assemblages from several wells in two localities of the West Siberian plain (Shaim oil and gas district, northwestern West Siberia, and Mykhpai field, central West Siberia). The assemblages are compared and studied in terms of space and time changes of their stratigraphy, which can make basis for a more detailed zonal subdivision as more data become available. The taxonomic compositions of the assemblages are summarized in tables for specific wells to highlight their geographic variations.

Callovian and Upper Jurassic foraminiferal and ammonite biostratigraphy of the Shaim petroleum region (West Siberia)

“…The zonal foraminiferal assemblage has a generally uniform taxonomic composition, with almost the same dominant species but of different numbers and diversity of taxa (Nikitenko et al, 2005). Zone JF25 was identified in 11 boreholes (BH-15, 19, 10268, 10257, 10262, 10527, 10292, 10554, 10054, 10374, and 8000) (Levchuk, 2009a (Levchuk, 2000). A similar assemblage of low diversity was recovered from Tugrovskaya BH-15 (2215.0-2219.6 m) after additional treatment of samples; it is dominated by agglutinated forms (Fig.…”