The Bilberry Hill or Overfold Quarry in the Lickey Quartzite is situated 600 m N.N.W. of Kendal End, near Birmingham. It is currently (July 2010) being cleared of vegetation and enlarged as an exhibition site by Worcestershire Earth Heritage Trust, in a project managed by Evelyn Miles. Work done for B.G.S. by S.G. Molyneux, twenty years ago, yielded organic-walled microfossils of early Ordovician age. This suggests that the best correlation would be to the Arenig Stiperstones Quartzite with Scolithos Haldeman vertical burrows, rather than to the basal Cambrian Tuttle Hill Member of the Hartshill Formation with paired U-shaped Burrows termed Arenicolites Salter. Both types of trace fossil have no age significance above the Precambrian. Arenicolites is the trace fossil name for the lug worm burrows still made in the mud on Southend Beach by Arenicola. It would, however, be instructive to determine whether the burrows now potentially becoming available on large sandstone slabs in the quarry consist of pairs of shafts termed Arenicolites, or the single if often numerous ones termed Scolithus. In Arenicolites the seawater is passed through the burrow, often preserved as a pair of funnel-like entrances, represented by domes on the sandstone base above it. The west side of the quarry shows a continuous succession of bands of sandstone and thin shales in the lower limb of the fold. Measured sections look different due to the absence of distinctive beds The south-east corner of the quarry showed green, glauconitic shales, laminated with 0.4 mm muscovite and clearly separated from similar shales at the base of the continuous section by a fault. It trends nearly parallel to the overfold on the west side of it. The fold axis plunges at 20° slightly W. of true north, judging from measured bedding planes around it. They include an intertidal channel cutting out about 0.1 m of sandstone at the fold axis. Measurements made here in July 9, 1978 with respect to Magnetic North (presumably 7° W of true N.) showed a dip of 21° S on a strike of 134° E. of Magnetic N. on the channel margin paleoslope, compared to 5° Mag. N. on a strike of 49°on the level bedding plane above the channel.
The talus cone yielding the fossil burrows was on the opposite N.W. side in the lower limb of the fold. This face showed 3 mm thick bands of arkose granules in sandstone at the base (below the burrow finds) with dips of 14°N. on 92° E of Mag. N and 20° N of 69° E of Mag. N there. At the tip of that talus cone (above the burrows) there was a 100 mm thick conglomerate band in arkose defining a dip of 39° N on a strike of 82° E of Mag. N. A considerably thicker, 1.2 m thick conglomerate was situated stratigraphically above these sandstone in the N.E. corner of the quarry, probably 27 m above the lowest upper shale beds.
I first visited the quarry, in March 20, 1976 with assistance from W.G. Hardie, to look for small shelly fossils by the same method as I was finding them in similarly barren-looking sandstones and conglomeratic sandstones in the upper part of the Cambrian Hartshill Quartzite. With a later 4.6 kg sample from the upper 0.1m of the 1.2m thick arkosic conglomerate on the north-east side of the quarry, and 2.75 kg of pure white quartzite of one mm grain size from near Whetly Lane below the Silurian Rubery Sandstone, my sample of rock surfaces viewed under a binocular microscope at x17.5 magnification had a mass of 18.3 kg. It consisted of rock chips split on a fly-press used to sample Ordovician brachiopods to cuboids in the 2 to 3 cubic cm size range. They proved to be barren of fossils but it is instructive to calculate the freshly exposed surface area studied. Since all the chips consisted of the quartzite, rather than shale and mud, it is reasonable the divided the sample mass by the density of the quartz or feldspar (2.6 g/ml) to deduce the volume of the sample and hence the number of chips of a particular size studied.
The talus cone yielding the fossil burrows was on the opposite N.W. side in the lower limb of the fold. This face showed 3 mm thick bands of arkose granules in sandstone at the base (below the burrow finds) with dips of 14°N. on 92° E of Mag. N and 20° N of 69° E of Mag. N there. At the tip of that talus cone (above the burrows) there was a 100 mm thick conglomerate band in arkose defining a dip of 39° N on a strike of 82° E of Mag. N. A considerably thicker, 1.2 m thick conglomerate was situated stratigraphically above these sandstone in the N.E. corner of the quarry, probably 27 m above the lowest upper shale beds.
I first visited the quarry, in March 20, 1976 with assistance from W.G. Hardie, to look for small shelly fossils by the same method as I was finding them in similarly barren-looking sandstones and conglomeratic sandstones in the upper part of the Cambrian Hartshill Quartzite. With a later 4.6 kg sample from the upper 0.1m of the 1.2m thick arkosic conglomerate on the north-east side of the quarry, and 2.75 kg of pure white quartzite of one mm grain size from near Whetly Lane below the Silurian Rubery Sandstone, my sample of rock surfaces viewed under a binocular microscope at x17.5 magnification had a mass of 18.3 kg. It consisted of rock chips split on a fly-press used to sample Ordovician brachiopods to cuboids in the 2 to 3 cubic cm size range. They proved to be barren of fossils but it is instructive to calculate the freshly exposed surface area studied. Since all the chips consisted of the quartzite, rather than shale and mud, it is reasonable the divided the sample mass by the density of the quartz or feldspar (2.6 g/ml) to deduce the volume of the sample and hence the number of chips of a particular size studied.
18.3 kg/2.6 x 1000 = 7038 cm3
Therefore:
2350 chips of 3 cm3, 3019 of 2 cm3 etc.
Actual chips from the quarry sample were measured up in mm and these volumes were found to correspond to areas split parallel to bedding of 6.3 and 4.0 cm2 respectively. Adding in the sides of the chips the total viewed area was about 3.5 m2
The lowest bed seen and sampled in the continuous section of March 1976 was a shale parting yielding chips of red sandstone split along planes of 0.8 to 2.0 mm muscovite. The average diameter of the feldspar was only 0.1 mm but this sample of 1.0 kg mass yielded one smooth ellipsoidal nodule or pebble of 3.5 mm length and numerous 0.2 mm rounded green grains which looked more like marine glauconite than altered volcanics.
The overlying sandstone bed of 390 mm thickness and 2.235 kg sampled mass had a parting 120 mm from the top and had a flat top covered by the next shale band reviewed below. This sandstone showed common glauconite grains in the 0.3 to 0.5 mm diameter range, rounded muscovite flakes ranging up to 2 mm in diameter and chlorite flakes of a similar size. The feldspar grain size was 0.2 mm. The mica produced a rather laminated rock, but in the field it looked massive with vertical jointing.
The overlying shale band of 70 mm thickness and 3.0 kg sampled mass was actually a complex unit consisting of an upper sandstone of about 10 mm thickness with a flat base and convoluted top bracketed by shale. Below this there was a thicker shale with a smooth surfaces on a lenticular 10 mm sand layer within it. When broken up the feldspar grain size was 0.1 to 0.3 and the muscovite and chorite 0.5 to 0.9 mm. Glauconite rounded grains were present at much the same size as the feldspar and scarce compared to the lower beds. There were white irregular patches, best interpreted as diagenetic veining rather than trilobite debris. The most interesting feature were grey shale clasts of 10 to 20 mm length, with a rounded lenticular shape in plane view and a thin flat sheet-like form in section. These mud flakes had evidently been ripped-up from a compacted mud layer and then rolled at their edges without distortion, producing skid mark lineations seen together with load casts in the sandstone at the top of the bed, and on the base of the overlying thicker sandstone reviewed next.
The sandstone above had an overall thickness of 900 mm before the next grey shale band was reached, but I only sampled the lowest 300 mm (4.0 kg) defined by a planar parting above and by an irregular, but less convoluted base below. The feldspar grain size was 0.2 to 0.3 mm, including some angular grains and scarce larger quartz grains of 1.0 mm were now present. The resulting rock was a pale red to grey quartzite, with very little shale or glauconite present. Probably this type of sandstone continues upwards in Bilberry Hill Quarry. The shale bands seen in the lower beds are rare above the channel. Towards the top they are associated with bands of coarser quartz and feldspar, as red distorted mud flakes from probable sun cracked intertidal mud flats. My upper samples consist of one of the grit bands (probably the one above the only talus cone yielding vertical burrows in sandstone) and the tip of the main conglomerate overlain by two metres of weathered rock and soil. The conglomerate included cm-sized volcanic clasts which were showed facets as in dreikanter from deserts and the distorted type of mud flakes. The grit band was composed of rather angular 0.5 mm quartz sand, with maximum dimension of 3 mm and larger volcanic fragments.
My collected sample of red burrowed sandstone was of lenticular shape with 0.2 to 0.8 mm diameter feldspar and muscovite grains, between two partings showing the vertical shaft to be at least 50 mm height. The lower surface showed the sandstone deflected downwards into a 7.3 mm diameter burrow, split at 4.4 mm diameter and 1.5 mm below the parting by a fracture of a sand-filled shaft. The upper surface was a saucer-like, 12 mm diameter depression, containing a pair of poorly defined central rings around the 7 mm shaft. This saucer appeared to have been truncated by a thicker but missing clay drape. It was not an Arenicolites-style entrance. There was no sign either of storm generated laminae in the host sandstone, or of the other shaft. But the distance of the shaft to the edges of the sandstone blocks were only 12 to 22 mm. This is not great enough to disprove the existence of the other shaft of an Arenicolites. In my sample from the Tuttle Hill Member, the enlarged entrances of 15 mm expanded diameter are spaced 22 mm apart in terms of the middle of their 5 mm diameter shafts. An identification as Diplocraterion can be discounted. The scarce occurrence of the burrows is itself a point of difference with normal Scolithos occurrences in Anglo-Welsh Ordovician sandstone. No others were seen outside part particular talus cone. Several doubtful paired shafts structures were observed, as well as considerably more common, subpolygonal ripped-up mudstone flakes from sun cracked surfaces.
