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.
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).
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).