Lower Bashkirian fusulinoideans from the upper part of the Tagnana Formation (Carboniferous, NW Algeria)

Abstract

The upper member of the Tagnana Formation of the Djebel Bechar Group (informally the Tagnana-3 or Tagnana Ill member) yielded fusulinoideans and other related foraminifera of the genera Pseudoendothyra (rare), Pseudostajfella (Semistaffella) (rare), Millerella, Pseudonovel/a, Plectostaffella, Eostaffella and Mediocris. The presence of Eostaffellina (rare) and Endostaffella is doubtful. The difference between Millerella and Eostaffella cannot be adequately defined by evolute versus involute coiling. Pseudonovella Kireeva, 1949 is redefined to include Seminovella Rauzer-Chernousova, 1951.

The foraminifera are from two samples, one from close to the top and the other from near the base of the Tagnana III Member. Conodonts from the same samples, in comparison with the fusulinoidean foraminifera indicate similar or slightly younger ages; combined evidence from conodonts and foraminifera shows that the Tagnana-III Member at its upper boundary is Askynbashky or Akavassky (probably late Akavassky), while its lower boundary is Akavassky or Siuransky (probably late Siuransky) in age.