Sedimentation in an Actively Tilting Half-Graben: Sedimentology and Stratigraphy of Late Tournaisian-Viséan (Mississippian, Lower Carboniferous) Carbonate Rocks in South County Wexford, Ireland

Abstract

The Wexford Basin (south-eastern Ireland) is a NE-SW-trending sedimentary basin containing carbonates and evaporites deposited during the Late Tournaisian and Viséan. Two separate depositional areas are defined on the basis of facies and facies associations. Sediments were deposited in inner ramp, lagoonal and peritidal environments near Rosslare, and in a more open-marine, shallow- to moderately deep-water, mid to outer ramp environment in the western area around Duncormick. Thick breccia deposits that occur in the Wexford Basin formed as a result of (i) fault movement that produced syn-sedimentary debris flows in the Late? Chadian (Breccia type I); (ii) dissolution of anhydrite/gypsum and subsequent collapse of sedimentary strata (Breccia type II); and (iii) fracturing and brecciation of porous rock caused by the movement of high temperature, late diagenetic fluids along fault planes (Breccia type III). The NE-SW facies polarity displayed by both sedimentary successions was the result of NW-SE extension and the reactivation of the NE-SW-trending Wexford Boundary Fault during the Chadian. Extension at the SE margin of the basin with downthrow to the NNW gave the basin a half-graben character. Thickening of the debris flow deposits to the SW suggests that while the half-graben was being tilted it also underwent a NE-SW block rotation due to an axial component of that normal fault.

Department(s)

Geosciences and Geological and Petroleum Engineering

Sponsor(s)

American Association of Petroleum Geologists
American Chemical Society
National Science Foundation (U.S.)
Petroleum Research Fund
University of Missouri Research Board

Keywords and Phrases

Wexford Basin; Lower Carboniferous; Syn-sedimentary Tectonics; Carbonates; Evaporites; Ireland; Lower Carboniferous; Syn-sedimentary Tectonics; Wexford Basin; Carbonates; Evaporites; Ireland

Time Period

Tournaisian
Viséan
Mississippian
Carboniferous

International Standard Serial Number (ISSN)

0037-0746

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2005 Wiley-Blackwell, All rights reserved.

Publication Date

01 May 2005

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