Sediment cyclicity and the Carnian Pluvial Episode: evidence from spectral gamma-ray logging of the Mercia Mudstone Group, SW England

Alastair Ruffell, Wolfram Kurschner

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2 Citations (Scopus)
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Abstract

The Late Triassic exposed on the Devon coast (SW England) is analysed through spectral gamma-ray logging and considered in terms of two theories of palaeoenvironmental change: sediment cyclicity and the Carnian Pluvial Episode (CPE). A decrease in total count gamma-ray output occurs at the CPE and reflects a geographically extensive change in depositional styles from siltstones and isolated playa-lake, evaporitic mudstones to more geographical-ly-widespread evaporite-bearing mudstone cycles. Th/K and Th/U ought to increase (through humid weathering) in the CPE, but these ratios do not change until above the CPE-related Dunscombe Mudstone Formation. A delayed response in Th enrichment is considered likely, reacting to both the initiation of the 1.2my long CPE, but also longer-term and widespread Carnian rifting, marine inundation and volcanism in Pangaea.

Original languageEnglish
Pages (from-to)231-242
JournalBoletín Geológico y Minero
Volume131
Issue number2
DOIs
Publication statusPublished - 18 Jun 2020

Keywords

  • Triassic, Carnian Pluvial Episode (CPE), spectral gamma-ray, palaeoclimate

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