Sedimentology, clay mineralogy and palaeosols of the Mid-Carnian Pluvial Episode in E Spain: insights into humidity and sea-level variations

Abstract

This study examines rainfall variations of the Mid-Carnian Pluvial Episode (CPE) based on the continental fluvial sedimentology, palaeosol and clay mineralogy records of the Stable Meseta (E Spain). In the formation examined, Manuel Fm or K2 Fm, the CPE is represented by three regressive-transgressive sequences (R-T), or subunits K2.1, K2.2 and K2.3, from base to top. Each subunit broadly consists of a genetic stratigraphic sequence bearing well-developed highstand, lowstand and transgressive system tracts (HST, LST and TST). Hydromorphic features in the palaeosols suggest changes in the activity of both ground and surface waters. The clay mineral assemblage is dominated by illite, with a minor presence of kaolinite and traces of smectite in some samples. After ruling out tectonism in the study area, climate and eustatism emerge as the main allogenic controls in the sedimentary record. Differentiated sedimentary facies and architectural elements in the K2.2 subunit were likely controlled by both a more humid climate and source area, while K2.1 and K2.3 were more related to base-level changes and eustatic control. The presence of more waterlogged pedotypes and of kaolinite and traces of smectite in the clay mineral assemblage of K2.2 also indicates increased humidity. Notwithstanding, our data do not point to intense rainfall periods for the CPE in E Spain.