Mid-Albian to earliest Cenomanian climate cycles indicated by humid paleosols developed within the arid braidplain facies of the Utrillas Group of east-central Spain

Abstract

The development of arid climate conditions in eastern Iberia during the mid-Cretaceous (mid-Albian to earliest Cenomanian) has been postulated by several authors over the last two decades based on sedimentological and palaeobotanical datasets. In this paper, we present a combined sedimentological and paleosol study of the mid-Albian to earliest Cenomanian Utrillas Group in the Cuenca Basin of east-central Spain, to improve knowledge of palaeoclimate. Four facies associations are identified as follows: Proximal alluvial braidplain (FA I), Distal alluvial braidplain (FA II), Aeolian dunes (FA III), and Inner estuarine settings (FA IV). The succession records the development of a braidplain system under dominantly arid conditions followed by a marine transgressive phase. In contrast to the overall arid palaeoclimate interpretation, multi-proxy palaeoedaphological analyses conducted for three paleosol profiles (Spodosols) indicate the occurrence of periods of increased humidity in the basin. These findings allow us to infer the occurrence of shorter-term climatic oscillations characterised by a tropical savanna climate when the palaeosols developed, suggesting significantly more humid conditions than those inferred based on the sedimentological and previous palaeobotanical datasets. We propose a palaeoclimatic model that explains the alternation between the dominantly arid and these more humid periods based on the cyclical latitudinal shifting of the mid-Cretaceous climatic belts, shedding new light on the mid-Albian to earliest Cenomanian climate of Iberia.