Cuarzo idiomorfo detrítico en la base del Cretácico Superior de la Depresión Intermedia (Navarra): implicaciones paleogeográficas

Abstract

In the southern border of the Bortzirí (Cinco Villas) Palaeozoic massif (Basque Pyrenees, Navarra) a narrow Alpine syncline known as the Central Depression consists mainly of Upper Ctreaceous calcareous flysch sediments. These sediments lie on different previous materials, from Carboniferous to Lower Cretaceous in age. In this work an inusual sandy unit at the base of the Upper Cretaceous series is studied. The petrographic features of this unit make it possible to differentiate two subunits, one basically litharenitic attributed to the Albian siliciclastic Black Flysch, and the other a matrix-supported lithoclastic wacke with abundant euhedral quartz, ophitic lithoclasts and planctonic foraminifera, attributed to the Upper Cretaceous calcareous flysch. The wacke subunit is interpreted to derive from adjacent horst(s), where Triassic material (mainly ophites and Keuper mudstones) had been eroded and concentrated in euhedral quartz