Stratigraphy, carbonate facies and trilobite associations in the Hirnantian part of the Boda Limestone, Sweden

Abstract

The Hirnantian (Upper Ordovician) sequence of the Boda Limestone is defined and described as a new formal Upper Boda Member. It has four petrologically distinct, bedded units containing three strikingly different trilobite faunas. These differences are thought to be caused by a sea-level lowering leading to the first Hirnantian sea-level lowstand and successive transgression as well as to shifts in sea-water chemistry. This is indicated by the occurrence of a level with botryoidal carbonate cement. On top follows the upper Hirnantian Glisstjärn Formation.