Diaz Martinez Enrique. (1996). Paleozoico inferior del Altiplano Norte de Bolivia. In :
Memorias del 12 congreso geologico de Bolivia. s.l. : s.n., p. 131-135. Congreso Geologico de Bolivia, 12., Tarija (BOL), 1996.
Titre du document
Paleozoico inferior del Altiplano Norte de Bolivia
Année de publication
1996
Type de document
Colloque
Auteurs
Diaz Martinez Enrique
In
Memorias del 12 congreso geologico de Bolivia
Source
s.l. : s.n., 1996,
p. 131-135
Colloque
Congreso Geologico de Bolivia, 12., Tarija (BOL), 1996
Several outcrops of pre-Cretaceous low-metamorphic-grade sedimentary and extrusive (volcanic and subvolcanic) rocks present in the northern Altiplano of Bolivia are herein interpreted as having a probable late Vendiant (?)-Early Paleozoic age. These rocks are present at three different localities: (a) Serrania Chilla (with Cerro Chilla rising to 4825 m), south of Tiwanaku, (b) Sewenkani and other creeks, north of Jesus de Machaca, and (c) several hills NW and N of Caquiaviri. the two first series of outcrops present a complex sedimentary sequence consisting of deep water, dark laminated shales and siltstones, interbedded with thin sandstone beds displaying typical Bouma sequences, and thicker beds of coaster sand, conglomerates and diamicitites. This sequence is here interpreted as part of a deep-sea fan system, although marine fauna and/or ichnofossils are yet to be found (palynological analysis gave no positive results). Thick (up to 50 m) beds of basic volcanic and subvolcanic rocks are also included in the sequence. These are identified by relics of pillow-lavas and flow structures, columnar jointing, differential core-to-contact crystallization degrees, and synsedimentary interaction with the soft sediment. The third series of outcrops does not present interbedded igneous rocks, nor the coaster clastic beds. Precious interpretations of these series of outcrops as an ophiolite or blastomylonitc belt are inconsistent with field evidence and should be disregarded. Instedad, these rocks are herein correlated with other deep-sea fan sequences also including interbedded volcanic and/or subvolcanic rocks, whick are found (1) in the late Vendiant(?)-Early Cambrian Puncoviscana Fm. of NW Argentina (San Cristobal Fm. of S Bolivia) and in the Ollantaytambo Series of southern Peru, and (b) in the Late Cambrian-Ordovician Sequence of the Eastern Cordillera of the Central Andes (southern Peru, Bolivia and northern Argentina) (Résumé d'auteur).
