Abstract

The western margin of the Loranca Basin is the Sierra Altomira, which separates it from the Madrid Basin. The eastern margin is formed by the Iberian Range, which supplied most of the Tertiary continental sediment that fills the Loranca Basin. This basin fill is divided into five units (I to V), ranging from Middle Eocene to Late Miocene in age. The tectonic and sedimentary evolution of the Basin has been analysed using outcrop and seismic mapping of the units and their folding, faulting and unconformities.

Introduction

The Loranca Basin, located in Central Spain, is separated from the Madrid Basin by the Sierra Altomira and bounded to the east by the Iberian Range (Fig. 1). The basin was filled by pre-and synorogenic Tertiary continental sediments, mainly sourced from the Iberian Range fold and thrust belt, which acted as the main active foreland.

The general stratigraphy of the Loranca Basin has been described by several authors (Vilas-Minondo & Pérez González, 1971; Meléndez Hevia, 1971; Viallard, 1973; Díaz-Molina, 1974; Garcia-Abbad, 1975; Díaz-Molina & López-Martinez, 1979; Díaz-Molina et al., 1985, 1989; Torres & Zapata, 1986-1987a, b; Torres et al., 1992).

Knowledge of the surface geology of the basin has been improved in the last few years by extensive regional mapping by ITGE. The results of this work have been reviewed and compiled in Fig. 2.