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BGS Technical Report WA/97/03 15 December 1997 At the east end of the hill, a further newly dug section [2834 32191 was revealed in an old ‘marl pit’ prior to infilling: Topsoil, slightly reddish brown, stony clay Mudstone, dark brick red 50150 mottled medium greenish grey Mudstone, brick red, silty, slightly shaly Mudstone, dark brick red 50150 mottled medium greenish grey Thickness (m) c. 0.5 c. 1.0 c. 1.1 c. 1.0 No exposure c. 1 Mudstone, brick red with a few pale green mottles, silty, slightly shaly, homogeneous c. 0.5 Siltstone, pale green, interlaminated with brick red siltstone 0.04 Mudstone, brick red with a few pale green mottles, silty, slightly shaly, homogeneous c. 1.2 Siltstone, variegated brick red and pale to medium greenish grey, soft; weathering crumbly and soft probably due to gypsum dissolution (see similar bed in above section) c. 0.6 Mudstone, brick red with small green mottles, silty, shaly c. 1.1 Mudstone, dark reddish brown mottled medium greenish grey, silty, shaly c. 0.3 Siltstone, pale green, shaly; forms floor of pit c. 0.3 Details: boreholes The Pastures Hospital Borehole SK 23 SEA9 [2968 33171 was drilled in the bottom of an existing well and penetrated white sand and marl possibly assigned to the Cotgrave Sandstone Member. It then proved 73.92 m of mainly ‘grey rock’, ‘red and grey marl’ and ‘marl’ with subordinate amounts of ‘red sandstone’, ‘blue shale’ and ‘rocky marl’; this sequence also included thin seams of white spar’ (gypsum?) in the upper 15 m. The Gunthorpe Formation was penetrated by numerous boreholes along the Derby Southern Bypass transect although the thickest sequences were proved on Sheet SK 22 NE (Brandon, 1997). The boreholes in the present area proved a typical sequence, at least 36 m thick, of deeply weathered, mainly red, mottled green, thinly to thickly interlaminated, silty mudstone and siltstone below various cryoturbated superficial deposits. Numerous thin beds of greenish grey siltstone are recorded below the deeply weathered zone along with gypsum veins in the lower part of the boreholes.The deeper boreholes occur in four groupings around the intersection with roads and streams: 1. Intersection with A516 (T) [2532 3120 - 2569 31081: This group of boreholes, e.g. boreholes SK 23 SE/186, 188, 190, 191, 193 and 196, contain strata that are generally deeply weathered to 12 m depth but two boreholes SK 23 SE/299 & 300 provided sections up to 25 m deep. The sequence apparently included fewer siltstone interbeds than boreholes at the other intersections. This might indicate a different level in the Gunthorpe Formation than that encountered in the other borehole groups although, since strata on the west side of the conjectural north - south Needwood Fault are only provisionally ascribed to the Gunthorpe Formation, it might indicate a different stratigraphical level in the Mercia Mudstone Group. .. 11. Intersection with Etwall Brook [2637 3089 - 2647 30841: boreholes SK 23 SE/201,210, 209 & 21 1 penetrated a typihal but weathered sequence down to 13 m depth. 8
BGS Technical Report WA/97/03 15 December 1997 iii. Intersection with Etwall Road [2682 3071 - 2697 30681: boreholes SK 23 SE/225,226 & 295 proved a typical sequence down to 17 m depth. Boreholes SK 23 SE/ 294 & 297 penetrated down to depths of 3 1 m and 25 m respectively. Although a typical interbedded mudstone/siltstone sequence was recorded in these two boreholes, they both proved sandstones in addition. Borehole SK 23 SE/294 [2682 30711 proved at least 9.27 m of interlaminated sandstone/siltstone at the base of the borehole, with a top boundary at a 35.75 m above OD. This unit is described as reddish brown, fine-grained, laminated, and argillaceous sandstone, thickly to thinly interlaminated with greyish green and white siltstone and reddish brown claystone. Borehole SK 23 SE/297 [2692 30711, sited only 100 m to the east, proved only 0.32 m of greyish green, fine-grained sandstone with laminations of reddish brown mudstone at 34.20 m above OD. iv. IntersectionwithA38 (T) [2901 3002 - 2927-30011: Boreholes SK 23 SE/323,325 & 331 penetrated through the thick cover of Elvaston Palaeochannel deposits into Gunthorpe Formation. Up to 12.8 m of undisturbed, unweathered, typically interlaminated mudstone and siltstone with gypsum veins were proved. A very similar sequence of up to 22 m of thinly interbedded to interlaminated reddish brown mudstones and green to ‘blue-grey’ siltstones with numerous gypsum veins were proved beneath 2.3 to 4.2 m of alluvium by site investigation boreholes SK 23 SE/141-150 [2661 3225 - 2669 32351 at the intersection of the Etwall Bypass with Etwall Brook and the adjacent railway. 4.2.4 Edwalton Formation The division (Elliot, 196 1) comprises mainly reddish brown and greyish green siltstone and mudstone which are typically blocky or very poorly laminated. Although thin beds of finegrained sandstone occur at many levels within the formation, thicker sandstone beds are concentrated at the base and top and form the Cotgrave and Hollygate Sandstone members. Wireline log signatures across the region suggest that the stratigraphy is persistent and the thickness maintains about 45 m. The formation is mostly Camian in age, although the basal part is possibly Ladinian (Oral communication, G W Warrington, 1997). The formation forms outcrops in the Etwall - Burnaston - Mickleover area. This is an interpretation based mainly on the identification of a feature-forming sandstone as the Cotgrave Sandstone Member, at the base of the formation. The upper part of the formation and the Hollygate Sandstone Member are not preserved in the area. The mudstones have been dug from numerous small ‘mar1 pits’ dotted over the outcrop (see Economic Geology section). Details: outcrop The formation is rarely exposed and is typically seen as c. 1 m of red clay in ditches and temporary exposures. Many of the exposures also have fragments of pale grey-green siltstone, commonly with salt pseudomorphs on the bedding surfaces. On Burnaston Hill, the following weathered section [2932 321 11 was,dug at a new barn at Hill Farm: 9
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