Abstract
AbstractThe formation of the supercontinent Pangaea during the Permo–Triassic gave rise to an extreme monsoonal climate (often termed ‘mega‐monsoon’) that has been documented by numerous palaeo‐records. However, considerable debate exists about the role of orbital forcing in causing humid intervals in an otherwise arid climate. To shed new light on the forcing of monsoonal variability in subtropical Pangaea, this study focuses on sediment facies and colour variability of playa and alluvial fan deposits in an outcrop from the late Carnian (ca 225 Ma) in the southern Germanic Basin, south‐western Germany. The sediments were deposited against a background of increasingly arid conditions following the humid Carnian Pluvial Event (ca 234 to 232 Ma). The ca 2·4 Myr long sedimentary succession studied shows a tripartite long‐term evolution, starting with a distal mud‐flat facies deposited under arid conditions. This phase was followed by a highly variable playa‐lake environment that documents more humid conditions and finally a regression of the playa‐lake due to a return of arid conditions. The red–green (a*) and lightness (L*) records show that this long‐term variability was overprinted by alternating wet/dry cycles driven by orbital precession and ca 405 kyr eccentricity, without significant influence of obliquity. The absence of obliquity in this record indicates that high‐latitude forcing played only a minor role in the southern Germanic Basin during the late Carnian. This is different from the subsequent Norian when high‐latitude signals became more pronounced, potentially related to the northward drift of the Germanic Basin. The recurring pattern of pluvial events during the late Triassic demonstrates that orbital forcing, in particular eccentricity, stimulated the occurrence and intensity of wet phases. It also highlights the possibility that the Carnian Pluvial Event, although most likely triggered by enhanced volcanic activity, may also have been modified by an orbital stimulus.
Highlights
To shed new light on the forcing of monsoonal variability in subtropical Pangaea, this study focuses on sediment facies and colour variability of playa and alluvial fan deposits in an outcrop from the late Carnian in the southern Germanic Basin, south-western Germany
The sediments were deposited against a background of increasingly arid conditions following the humid Carnian Pluvial Event
The recurring pattern of pluvial events during the late Triassic demonstrates that orbital forcing, in particular eccentricity, stimulated the occurrence and intensity of wet phases
Summary
The formation of the supercontinent Pangaea during the Permo–Triassic led to a distinct global configuration of an azonal climate pattern with a dominance of monsoonal wind systems in (sub)tropical latitudes (Parrish & Peterson, 1988; Kutzbach & Gallimore, 1989; Sellwood & Valdes, 2006) that caused the alternating occurrence of extreme wet and dry seasons over Pangaea (Parrish & Peterson, 1988; Dubiel et al, 1991; Mutti & Weissert, 1995) The development of this ‘mega-monsoon’ originated from the strong warming of Laurasia (Northern Hemisphere) relative to Gondwana (Southern Hemisphere) during boreal summer and vice versa (Kutzbach & Gallimore, 1989; Kutzbach, 1994). These high pCO2 concentrations impacted the radiative forcing, thereby increasing the land–ocean temperature contrast that drives monsoonal wind systems (Lee & Wang, 2014; Mohtadi et al, 2016; Wang et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
