Calpionellid and nannoconid stratigraphy and microfacies at the Tithonian-Berriasian boundary in the Sierra del Infierno (western Cuba)

Abstract

Stratygrafia kalpionellidowa i nannokonusowa oraz mikorfacje wapieni występujących w pobliżu granicy tyton-berias w Sierra del Infierno (Zachodnia Kuba) The radiolarian and calpionellid microfacies are characteristic for the latest Tithonian–Early Berriasian limestones of the Guasasa Formation in the Sierra del Infierno, western Cuba. The limestones of the uppermost part of the El Americano Member belong to the Late Tithonian Crassicollaria intermedia Subzone, Crassicollaria Standard Zone, and to the basal part of the Early Berriasian Calpionella alpina Subzone. The lower part of the Tumbadero Member is assigned to the C. alpina Subzone of the Calpionella Standard Zone. A heteromorph ammonite assemblage (Protancyloceras-Vinalesites) crosses the Crassicollaria/Calpionella Zones boundary. The studied limestones belong to three nannoconid assemblages of latest Tithonian–Early Berriasian age assigned to Nannoconus wintereri Subzone, N. steinmannii minor Subzone and N. steinmannii steinmannii Zone. Radiolarian taxa identified in thin sections are consistent with the lower part of D2 radiolarian zone from Western Tethys. The investigated deposits have been probably accumulated in the dysaerobic zone. At the Tithonian–Berriasian (J/K) boundary, dysaerobic to anaerobic conditions could be widespread in the deeper waters of the northwestern Proto-Caribbean basin.