New evidence of the Cretaceous overstep of the Mendip Hills, Somerset, UK

Abstract

The Mendip Hills, located on the north-western margin of the Wessex Basin, clearly show the onlap of Upper Triassic to Middle Jurassic sediments onto folded Palaeozoic strata. Recent field mapping on the crest of the Beacon Hill pericline at Tadhill, near Frome, augmented by a suite of shallow boreholes, proved up to 6.2 m of glauconitic grey and green silty sand. These glauconitic sands rest unconformably on Silurian volcanic rocks and Devonian sandstone. Lithological and palaeontological analyses of these glauconitic sands indicate that they are part of the Lower Cretaceous Upper Greensand Formation. This provides the first evidence for the Albian transgression across the Mendip Hills. The implications for the Cretaceous overstep on the margins of the Wessex Basin, and the analogies with the Upper Greensand succession in Devon are discussed.

The Isle of Wedmore relay ramp: how fault evolution created King Alfred's historic landmark

“…, fringed by Permo-Triassic and Mesozoic rocks, and onlapping Upper Triassic to Lower Cretaceous rocks (e.g.,Farrant et al, 2014). Similar Variscan structures occur to the north, including the area of the Lulsgate Plateau (maximum height = 202 m) and the hills around the Gordano Valley (maximum height = 136 m), and these Variscan structures can also be traced westwards to the coast, including at Brean Down (maximum height = 97 m) and Middle Hope (maximum height = 48 m).3.…”

Proceedings of the Geologists’ Association (PGA) Volume 126, Issue 1

“…consider the regional stratigraphy of Campanian phosphorites in Egypt;Farrant et al (2014) present new evidence for the Cretaceous overstep in part of southwest England;Barron and Riding (2014) propose a revision of the Jurassic lithostratigraphy in northeast Scotland;Cope (2015) describes a detailed lithostratigraphy for the Kimmeridge Clay in southern England and Wright (2014) describes a new section through the Corallian Group in Wiltshire, southern England. The others consider aspects of palaeoecology and palaeontology Donovan et al (2014b).…”