Triassic ammonoid biostratigraphy: an overview

Abstract

The Triassic chronostratigraphic scale was built on two centuries of research on ammonoid biostratigraphy and biochronology. Two Triassic stage bases and all of the Triassic substages are currently defined by ammonoid bioevents. The study of Triassic ammonoids began during the late 1700s, and in 1895, Edmund von Mojsisovics, Wilhelm Waagen and Carl Diener published an essentially complete Triassic chronostratigraphic scale based on ammonoid biostratigraphy. This scale introduced many of the Triassic stage and substage names still used today, and all terminology of stages and substages subsequently introduced has been based on ammonoid biostratigraphy. Early Triassic ammonoids show a trend from cosmopolitanism (Induan) to latitudinal differentiation (Olenekian), and the four Lower Triassic substage (Griesbachian, Dinerian, Smithian and Spathian) boundaries are globally correlated by widespread ammonoid biotic events. Middle Triassic ammonoids have provinciality similar to that of the Olenekian and provide a basis for recognizing six Middle Triassic substages. Late Triassic ammonoids provide a basis for recognizing three stages divided into five substages. The main uncertainty for the future of Triassic ammonoid biostratigraphy is not the decline of the ammonoids as a tool for dating and correlation of Triassic strata but, rather, the dramatic decrease in the number of specialists, due to the lack of replacement of experienced palaeontologists who started their activity in the 1950s and 1960s.

Ammonoid diversification in the Middle Triassic: Examples from the Tethys (Eastern Lombardy, Balaton Highland) and the Pacific (Nevada)

“…Their detailed stratigraphic correlation was also carried out (Monnet et al 2008;Vörös et al 2009;Balini et al 2010) and this was applied in the present paper in a somewhat simplified form (Table 1). The names and the spans of the ammonoid zones and subzones partly differ in the three areas.…”

“…The Mesozoic history of the ammonoids shows two major, distinct evolutionary cycles: one in the Triassic and, after a near-extinction at the end-Triassic a second one in the Jurassic-Cretaceous (Arkell et al 1957;House 1988). The Triassic phylogenetic radiation and diversification, recorded mostly in the group of Ceratitida, was further analyzed in detail by Tozer (1981) and recently by Brayard et al (2009) and Balini et al (2010).…”

The Triassic timescale: an introduction

“…In this volume, Lucas (2010a) reviews the historical development of the Triassic chronostratigraphic scale, which is largely a review of the application of ammonoids to Triassic chronostratigraphy. Also, in this volume, Balini et al (2010) review Triassic ammonoid biostratigraphy. The study of Triassic ammonoids began during the late 1700s, and Mojsisovics et al (1895) published an essentially complete Triassic chronostratigraphic scale based on ammonoid biostratigraphy.…”

First record ofRhabdoceras suessi(Ammonoidea, Late Triassic) from the Transylvanian Triassic Series of the Eastern Carpathians (Romania) and a review of its biochronology, paleobiogeography and paleoecology

“…This is already given, but not explicitly stated, by Krystyn et al (2009), Lucas (2010 and Balini et al (2010).…”