Detailed 3-D depositional architecture of Late Jurassic carbonate-anhydrite cycles (Brightling Mine, Weald Basin, UK)
File(s)
Accepted version
Author(s)
Abbott, SS
John, CM
Fraser, AJ
Type
Journal Article
Abstract
Quantifying the geometries of evaporite deposits at a <1 km scale is critical in our understanding of similar ancient depositional systems, but is challenging given evaporite mineral dissolution at surface conditions. A high-resolution stratigraphic study of the basal Purbeck Beds in Brightling Mine, UK, provides insight into the three-dimensional architecture, lateral continuity and vertical heterogeneity within an evaporite seal. We conducted a field mapping study, combined with X-ray diffraction, petrographic microscopy, and δ13C and δ18O isotope analysis. The stratigraphic interval contains five facies. In stratigraphic order, these include supratidal porphyritic nodular evaporite, shallow subtidal peloidal packstone with evaporite and two overlying rhythmic sequences of intertidal microbial laminite, subtidal shale, and subtidal laminar marl, capped by nodular anhydrite. The interpreted environment of deposition is a supratidal sabkha subject to periodic flooding in which intertidal (tidal flat) facies and subtidal (shallow marine) facies laterally passed into the evaporative sabkha. The cycles are interpreted as meter-scale shoaling-upward sequences, likely controlled by localized high-frequency changes in relative sea level and/or sabkha hydrology. Spatial patterns in the geometries of key stratigraphic surfaces reveal a subtle depression towards the central western region of the mine seam. The variation in stratal geometries is interpreted as paleotopography and is a function of individual or composite processes related to dissolution, eolian processes, and coastal erosion. These observations indicate a similar mode of deposition to the modern-day sabkha of the Persian Gulf. We conclude that the dynamic process of evaporite deposition led to subtle stratigraphic heterogeneities and changes in bed thicknesses, but largely continuous lateral bedding at an interwell-scale.
Date Issued
2015-10-19
Date Acceptance
2015-10-15
Citation
Marine and Petroleum Geology, 2015, 69, pp.74-93
ISSN
1873-4073
Publisher
Elsevier
Start Page
74
End Page
93
Journal / Book Title
Marine and Petroleum Geology
Volume
69
Copyright Statement
© 2015, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
Qatar Petroleum
Grant Number
N/A
Subjects
Science & Technology
Physical Sciences
Geosciences, Multidisciplinary
Geology
Heterogeneity
Carbonate-evaporite cycles
Interwell-scale
Sabkha
Lateral continuity
Evaporite seal
Purbeck Beds
Weald Basin
EASTERN NORTH-AMERICA
SOUTHERN ENGLAND
ARABIAN GULF
ABU-DHABI
WESSEX BASIN
ALGAL MATS
SEQUENCE STRATIGRAPHY
WESTERN-AUSTRALIA
BAJA CALIFORNIA
RIFT BASIN
Publication Status
Published