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How to get a date in the Devonian of Bolivia
18/12/2004 00:00 | Durée 00:14:48

Intervenants : Ian Troth , School of Ocean and Earth Science, Southampton Oceanography Centre, European Way, Southampton, UK .  

During the Mid Palaeozoic Bolivia was part of the Malvinokaffric Province, a high-latitude southern hemisphere realm that had a highly endemic marine fauna. This makes dating and correlation with Euramerica by macrofossils difficult, but microfossils have proved more useful. A succession of microplankton ‘events’ has been recorded throughout the Devonian of Bolivia that comprise short-lived monospecific pulses of distinctive marine palynomorphs. Particular emphasis in this study has been placed on the Evittia sommeri event, dated by cosmopolitan chitinozoan and spore taxa as latest Emsian/early Eifelian. Sedimentology shows the E. sommeri event is associated with a major marine transgression that, based on the earliest Mid Devonian date, can be considered the Chotec Event. This is the first time the Chotec Event has been identified at high palaeolatitudes and its recognition has allowed a test of the Euramerican sea-level curve. Preliminary results of the Mid/Late Devonian in Bolivia show that the sea-level curve should be regarded with caution through this interval.