A Boreal Toarcian Biochronological Zonation Based on Bivalve Mollusks of the Genus Meleagrinella Whitfield, 1885

Abstract

Using the chronological sequence of species of the genus Meleagrinella Whitfield, 1885 (family Oxytomidae Ichikawa, 1958) established in the Toarcian deposits of Northeast Russia, eastern Siberia, and southern Germany, a biochronological zonation is proposed for the Lower Toarcian. Three oxyto-zones corresponding to zones of the Boreal Ammonite Scale are established: Meleagrinella golberti oxyto-zone = Til-toniceras antiquum and Harpoceras falciferum zones; Meleagrinella substriata oxyto-zone = Dactylioceras commune Zone; Meleagrinella prima oxyto-zone = Zugodactylites braunianus and Pseudolioceras compac-tile zones. Using the proposed zonation, an interregional correlation of sections of the Lower Toarcian of Northern Russia (Astronomicheskaya, Saturn, Brodnaya, Start rivers), eastern Siberia (Anabar Bay, Markha, Tyung, Vilyui, Kelimyar, Motorchuna river, and boreholes in the Vilyui Syneclise) and southern Germany (the Ludwig Canal) is performed.