Mineralogy and palaeoenvironments: the Weald Basin (Early Cretaceous), Southeast England

Abstract

Determination of the mineralogy of sedimentary rocks is important in palaeoenvironmental interpretations, especially when outcrop and field data are insufficient or not accessible. The Lower Cretaceous Wealden facies, presented here as a case study, is one such example. Petrographic analysis of this suite of sediments reveals that the arenaceous facies are mainly quartz arenites, quartzose siltstones and lack significant feldspar. The clay minerals are illite, kaolinite, illite-montmorillonite, vermiculite and illite-smectite. The presence of quartz arenites and kaolinite suggests that the rocks were reworked from granitic and/or gneissic rocks. Directly or indirectly, the rocks may have been obtained from a stable craton. The mineral and textural maturity, together with a travel distance of ca 300 km point to matured sources. A warm and humid palaeoclimate in the source areas resulted in extensive weathering.