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The middle Ordovician Jurcuma section: A pinpoint for the basin evolution in southern Bolivia

by Sven O. Egenhoff, Freiberg; Jörg Maletz, Buffalo; Bernd Weber, & Bernd-Dietrich Erdtmann, Berlin


EGENHOFF, S.O.; MALETZ, J.; WEBER, B. & ERDTMANN, B.-D. (2002): The middle Ordovician Jurcuma section: A pinpoint for the basin evolution in southern Bolivia. - Freiberger Forschungshefte C 497: Paläontologie, Stratigraphie, Fazies (10): 9-17; Freiberg.

Abstract

A ca. 500 m long section through middle Ordovician strata is exposed in the Quebrada de Jurcuma and can be dated by the record of graptolites as of Hustedograptus teretiusculus Biozone (late Darriwilian) age. The siliciclastic sediments of the Jurcuma Formation were deposited in a storm-dominated environment not far from the coastline. The monotonous facies development in the section indicates a stable position of the coastline in the late Arenig to late Darrriwilian. The exposition of large parts of the lower Ordovician shelf of southern Bolivia remained stable in the middle Ordovician. The geometry of the mid-Ordovician basin, therefore, shows it to be considerably narrower than in the early Ordovician (Tremadoc - early Arenig).

Zusammenfassung

A ca. 500 m long section through middle Ordovician strata is exposed in the Quebrada de Jurcuma and can be dated by the record of graptolites as of Hustedograptus teretiusculus Biozone (late Darriwilian) age. The siliciclastic sediments of the Jurcuma Formation were deposited in a storm-dominated environment not far from the coastline. The monotonous facies development in the section indicates a stable position of the coastline in the late Arenig to late Darrriwilian. The exposition of large parts of the lower Ordovician shelf of southern Bolivia remained stable in the middle Ordovician. The geometry of the mid-Ordovician basin, therefore, shows it to be considerably narrower than in the early Ordovician (Tremadoc - early Arenig).