A Mid-Carboniferous Boulder-bed near Settle

Abstract

(1) The blocks of limestone in the Bowland Shales of School Share include a variety of rock-types of northern (Yoredale) facies and come from several beds near the Orionastraea Band of the Upper Viséan.(2) They are a local accumulation at the local base of the Namurian (Upper Bowland Shales; zone of Eutnorphoceras pseudobilingue, E1 and rest, with evidence of some slight erosion, on one of the highest horizons of the Viséan (Lower Bowland Shales; zone of Goniatites spiralis, P2). Their horizon, therefore, is that of the mid-Carboniferous unconformity of Settle and elsewhere.(3) They mark a comparatively small faunal hiatus (between the newsomi-meslerianum level immediately below and the C. malhamense level above).(4) Their separation from the parent rocks and their assemblage are not due to tectonic causes. On the other hand, their great size points to some unusual form of transport.(5) As they occur in a shale series near the Craven Faults they may legitimately be explained as the result of land-slips down s muddy slope from a limestone cliff, probably a fault-scarp raised by the mid-Carboniferous earth-movement.(6) The circumstances recall those attending the Lower Palaeozoic conglomerates of Quebec. A recent explanation ascribes these to landslips caused by earthquakes from submarine fault-scarps. The School Share landslip may well have been caused by earthquakes, and the scarp from which the blocks were derived may have been essentially submarine.