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New information on Neoproterozoic-Cambrian geology and the Triassic unconformity around Groby, southern Charnwood Forest, UK

Philip M. Scotney, John N. Carney and Mark Harwood
New information on Neoproterozoic-Cambrian geology and the Triassic unconformity around Groby, southern Charnwood Forest, UK
Proceedings of the Yorkshire Geological Society (May 2012) 59 (1): 37-51

Abstract

Detailed investigations utilizing borehole drilling, geophysical techniques and revision mapping have elucidated the geological evolution of southern Charnwood Forest. This study confirms that the South Charnwood Diorite was emplaced in latest Neoproterozoic times and has a broadly concordant intrusive contact with underlying volcaniclastic strata of the Charnian Supergroup. Following erosion that unroofed the diorite, an Early Cambrian marine transgression deposited an unconformable covering of Brand Group strata. In end-Silurian times, the region experienced orogenic compression and folding along a dominant NW-WNW tectonic grain. "Phase 1" structures with these orientations include the Charnwood Anticline and a transecting, penetrative cleavage that is mainly developed in the stratiform Charnian rocks. Further manifestations of this deformation were systems of NW-trending faults, the most important of which is the Groby Reverse Fault. This complex structure is described here for the first time; it features a narrow tectonic slice of Brand Group rocks, which was thrown down into the South Charnwood Diorite. The courses of younger, "Phase 2" faults are also revealed by the present study; they are orthogonal to, and thus offset the earlier NW structures. During Permian times, the area was stripped of its Carboniferous cover, resulting in a rugged pre-Triassic topography. This study has shown that the South Charnwood Diorite was eroded into low-lying, NW-elongated, steep-sided domes (bornhardts). It has also revealed the configuration of an associated paleo-valley system, which suggests that regional tilting associated with development of the syn-Triassic Hinckley Basin to the southwest of Charnwood Forest may have influenced drainage directions before burial of the hill-range beneath desert sediments of the Mercia Mudstone Group.


ISSN: 0044-0604
EISSN: 2041-4811
Coden: PYGSAB
Serial Title: Proceedings of the Yorkshire Geological Society
Serial Volume: 59
Serial Issue: 1
Title: New information on Neoproterozoic-Cambrian geology and the Triassic unconformity around Groby, southern Charnwood Forest, UK
Affiliation: Natural History Museum, Department of Mineralogy, London, United Kingdom
Pages: 37-51
Published: 201205
Text Language: English
Publisher: Yorkshire Geological Society, Leeds, United Kingdom
References: 62
Accession Number: 2017-021426
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 1 table, geol. sketch maps
N52°30'00" - N53°00'00", W01°40'00" - W00°40'00"
Secondary Affiliation: British Geological Survey, GBR, United KingdomTerraDat UK, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201715
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