Provenance of siliciclastic and hybrid turbiditic arenites of the Eocene Hecho Group, Spanish Pyrenees: implications for the tectonic evolution of a foreland basin

Abstract

International audienceThe Eocene Hecho Group turbidite system of the Ainsa-Jaca foreland Basin (southcentral Pyrenees) provides an excellent opportunity to constrain compositional variations within the context of spatial and temporal distribution of source rocks during tectonostratigraphic evolution of foreland basins. The complex tectonic setting necessitated the use of petrographic, geochemical and multivariate statistical techniques to achieve this goal. The turbidite deposits comprise four unconformity-bounded tectonostratigraphic units (TSU), consisting of quartz-rich and feldspar-poor sandstones, calclithites rich in extrabasinal carbonates and hybrid arenites dominated by intrabasinal carbonates. The sandstones occur exclusively in TSU-2, whereas calclithites and hybrid arenites occur in the overlying TSU-3, TSU-4 and TSU-5. The calclithites were deposited at the base of each TSU and hybrid arenites in the uppermost parts. Extrabasinal carbonate sources were derived from the fold-and-thrust belt (mainly Cretaceous and Palaeocene limestones). Conversely, intrabasinal carbonate grains were sourced from foramol shelf carbonate factories. This compositional trend is attributed to alternating episodes of uplift and thrust propagation (siliciclastic and extrabasinal carbonates supplies) and subsequent episodes of development of carbonate platforms supplying intrabasinal detrital grains. The quartz-rich and feldspar-poor composition of the sandstones suggests derivation from intensely weathered cratonic basement rocks during the initial fill of the foreland basin. Successive sediments (calclithites and hybrid arenites) were derived from older uplifted basement rocks (feldspar-rich and, to some extent, rock fragments-rich sandstones), thrust-and-fold belt deposits and from coeval carbonate platforms developed at the basin margins. This study demonstrates that the integration of tectono-stratigraphy, petrology and geochemistry of arenites provides a powerful tool to constrain the spatial and temporal variation in provenance during the tectonic evolution of foreland basins

Erosion rates in the source region of an ancient sediment routing system: comparison of depositional volumes with thermochronometric estimates

“…Palaeocurrent data show that the dominant palaeoslope was towards the west (Fig. 2), supporting previous palaeogeographical reconstructions (Bentham et al 1992;Nijman 1998;Dreyer et al 1999;remacha et al 2005;Das Gupta & Pickering 2008;Caja et al 2010;Whitchurch et al 2011). Palaeocurrent data also indicate that two major palaeovalley systems (Sis and Gurb-Pobla) dispersed sediment towards the south from the Pyrenean mountain belt (Mellere 1993;Vincent 2001;Whittaker et al 2011;Parsons et al 2012;Michael 2013), swinging towards the west in the southern Tremp Basin owing to deflection by the topography caused by the Montsec thrust system (Millán et al 1994;Allen et al 2013).…”

Formation of chlorite during thrust fault reactivation. Record of fluid origin and P–T conditions in the Monte Perdido thrust fault (southern Pyrenees)

“…4c). A detailed petrographic description of the Hecho group sandstones is given in Caja et al (2009). In sandstones, the major phase is detrital quartz (Fig.…”

Large scale facies change in the middle Eocene South-Pyrenean foreland basin: The role of tectonics and prelude to Cenozoic ice-ages

“…11). These maps summarize information from the works of Séguret (1972), Puigdefàbregas (1975) and Mutti (1977) for the Jaca basin, Plaziat (1981) for the whole South-Pyrenean basin, Lanaja (1987) for the buried sediments of the Jaca and Ebro basins, Millán (1996) and this study for the southern border of the Jaca basin, Payros (1997) and Payros et al (1999) for the south-western foreland region of Pamplona, Bentham et al (1992), Nijman (1998) Dreyer et al (1999) and Caja et al (2010) for the Ainsa basin, and Lopez-Blanco (2002), Serra-Kiel et al (2003) and Vera (2004) for the eastern foreland. In addition we have also used the geological maps of the Arguís area (José et al, 1951), Catalunya (Losantos et al, 1989) and our own field data.…”