@article{Jackson:2013:10.1130/B30833.1,
author = {Jackson, CAL and Schofield, N and Golenkov, B},
doi = {10.1130/B30833.1},
journal = {Geological Society of America Bulletin},
pages = {1874--1890},
title = {Geometry and controls on the development of igneous sill-related forced folds: a 2D seismic reflection case study from offshore southern Australia},
url = {http://dx.doi.org/10.1130/B30833.1},
volume = {125},
year = {2013}
}

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TY  - JOUR
AB  - Emplacement of magma in the shallow subsurface can result in the development of dome–shaped folds at the Earth's surface. These so-called "forced folds" have been described in the field and in subsurface data sets, although the exact geometry of the folds and the nature of their relationship to underlying sills remain unclear and, in some cases, controversial. In this study we use high-quality, two-dimensional (2-D) seismic reflection and borehole data from the Ceduna sub-basin, offshore southern Australia, to describe the structure and infer the evolution of igneous sill–related forced folds in the Bight Basin igneous complex. Thirty-three igneous sills, which were emplaced 200–1500 m below the paleo-seabed in Upper Cretaceous rocks, are mapped in the Ceduna sub-basin. The intrusions are expressed as packages of high-amplitude reflections, which are 32–250 m thick and 7–19 km in diameter. We observe five main types of intrusion: type 1, strata-concordant sills; type 2, weakly strata-discordant, transgressive sills; type 3, saucer-shaped sills; type 4, laccoliths; and type 5, hybrid intrusions, which have geometric characteristics of intrusion types 1–3. These intrusions are overlain by dome-shaped folds, which are up to 17 km wide and display up to 210 m of relief. The edges of these folds coincide with the margins of the underlying sills and the folds display the greatest relief where the underlying sills are thickest; the folds are therefore interpreted as forced folds that formed in response to emplacement of magma in the shallow subsurface. The folds are onlapped by Lutetian (middle Eocene) strata, indicating they formed and the intrusions were emplaced during the latest Ypresian (ca. 48 Ma). We demonstrate that fold amplitude is typically less than sill thickness even for sills with very large diameter-to-depth ratios, suggesting that pure elastic bending (forced folding) of the overburden is not the only process a
AU  - Jackson,CAL
AU  - Schofield,N
AU  - Golenkov,B
DO  - 10.1130/B30833.1
EP  - 1890
PY  - 2013///
SP  - 1874
TI  - Geometry and controls on the development of igneous sill-related forced folds: a 2D seismic reflection case study from offshore southern Australia
T2  - Geological Society of America Bulletin
UR  - http://dx.doi.org/10.1130/B30833.1
UR  - http://gsabulletin.gsapubs.org/cgi/content/abstract/125/11-12/1874
VL  - 125
ER  - 

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