Catodoluminiscencia de carbonatos lacustres pérmicos de los Pirineos Occidentales: un modelo de cementación temprana en paleoacuíferos meteóricos asociados a lagos

Abstract

Cathodoluminescence of Permian lacustrine carbonates from the Westem Pyrenees: a model for early cementation in meteoric aquifers associated with lakes. We present here a case-study of early diagenetic cementation in Permian lacustrine lithofacies (Aragón-Béarn and Basque Country Basins, western Pyrenees). Cathodoluminescence zoning in calcite cements shows a general non-luminescent-bright luminescent-dull luminescent sequence which we interpret as a result of the transition from the vadose and oxic phreatic environments to the progressively reducing phreatic ground waters. Vadose features and non-lumines-cent cements predominate in the more  pedogenically altered andlor subaerially exposed facies. The very early timing of the whole sequence and the differences in cementation among lacustrine, palustrine and

alluvial plain facies emphasize the dependence of the aquifers on sedimentary subenvironments and lake level changes. The Permian model here described is applicable to early cementation in meteoric aquifers related to shallow, carbonate lakes. Our data agree with the well-known control of Fe and Mn contents on the cathodolurninescence of calcites and dolomites and the uncertainties of a quantitative relationship between chernical composition and luminescence. The proposed sensitizer role for Mg needs further testing.