Page 31 - An Atlas of Carboniferous Basin Evolution in Northern England

18 Chapter 3

Fig. 15. High-resolution depositional sequences and component systems tracts from the northern margin of the Widmerpool Gulf for the upper part of seismic sequence LC1 (LClc), between R. gracile and G. subcrenatum marine bands (see Fig. 11 for location of wells). After Church
& Gawthorpe (1994).

tuffaceous units occur sporadically towards the base of the unit. The upper part Conodont faunas from the lower part of the LC1 sequence are diverse, and as Hathern Shelf and, to a lesser extent, the Widmerpool Gulf were inverted.
of the sequence is represented by a series of shallowing upwards deltaic cycles well as G. girtyi collinsoni include G. girtyi intermedius, G. bilineatus bilineatus, Evidence of inversion within the Widmerpool Gulf is provided by the
consisting of interbedded sandstones and grey mudstones, each of which Neoprionoidus spathatus subsp. A, N. scitulus, Cavusgnathus naviculus and P. northward offset from the Hoton Fault of the thickest part of the LC1
becomes progressively sandstone-dominated towards the top (Fig. 14). commutatus (Ebdon et al. 1990). At the base of the sequence, brachiopod spines sequence (Fig. 12). LC1 is divisible into a number of higher frequency seismic
Sequence stratigraphic analysis of these deltaic cycles suggests they represent and the internal casts of foraminifers are important accessories to the sequences (Figs 12 and 14), and high-resolution depositional sequences and
high frequency depositional sequences reflecting relative sea-level changes (e.g. microfauna. The palynoflora remains unchanged from the underlying constituent systems tracts based on borehole and outcrop data (e.g. Church &
Church & Gawthorpe 1994; Fig. 15). sequence, being assignable at the base of LC1 to the NC Zone (Neves et al. Gawthorpe 1994; Fig. 15). The sediments of LC1 are not generally fault
1972). controlled and represent an overall progradational sediment package deposited
Biostratigraphy. The boundary between the LC1 sequence and the underlying during the initial stages of thermal subsidence that followed Dinantian rifting.
EC6 sequence equates to the boundary between the G. girtyi collinsoni Zone Interpretation. Following EC6 there was a minor inversion event, with the The earliest sediments of LC1 are distal prodelta mudstones and basinal
(Varker & Sevastopulo 1985) and the G. bilineatus Zone (Metcalfe 1981). strongest inversion concentrated along NNW-SSE-trending faults. Both the turbidites of the advancing Silesian delta system which had already filled basins