The geology of the Cinqueta region, Spanish Pyrenees, province of Huesca

Abstract

In the investigated area rocks are exposed of which the ages probably range from Cambro-Ordovician to Upper Triassic. The pre-Hercynian sedimentary rocks generally show a low grade dynamo-metamorphism, upon which is superposed a thermal metamorphism related to the intrusion of late Hercynian granodiorites. Regional metamorphic rocks also occur, but they are restricted to the northern part of the area (Cinqueta de la Pez unit). The following lithostratigraphic units were distinguished in the preHercynian sedimentary rocks : The Cinqueta de la Pez complex, consisting of regional-metamorphic sandy and pelitic sediments which are generally attributed to the CambroOrdovician. The Vilados Formation, constituted by slates, hornfelses and quartzites, which represent the non- or thermally metamorphosed equivalent of the Cinqueta de la Pez complex. The Madera Formation consists of black coal-bearing shales with some dark limestones at the top. This unit is attributed to the Gotlandian and probably ranges into the Lower Devonian (Lower Gedinnian). It is overlain by an alternation of limestones and slates in which four formations are distinguished The Puyaresto Formation (an alternation of marly limestone and sandy slate). the Ardana Formation (massive limestones), the Sein Formation (sandy slates with a few marly limestones in the upper part) and the Barbarisa Formation (calc-schists, marly limestones and thin layers of sandy slate). This sequence probably ranges in age from the Lower Gedinnian into the Eifelian (Lower Devonian and lower Middle Devonian). The pre-Hercynian series is terminated by the slates of the Sahun Formation, which may be of Carboniferous age. The crystalline Paleozoic is represented in the Cinqueta region by the Rechanzadas-Descubridores and Cinqueta granodiorites with their associated dikes.