Carboniferous biostratigraphy of the Rookhope Borehole, Co. Durham

Abstract

A deep borehole drilled at Rookhope in Weardale, Co. Durham in 1960–61 proved the Weardale Granite below Carboniferous sediments at a depth of 390 m; an account of the Carboniferous rocks is presented. The boring commenced in the basal Namurian Great Limestone and entered the Dinantian at the bottom of the limestone at 25 m. Most of the ten Brigantian cyclothems sectioned in the borehole are compound and average 30 m thick. They consist of an initial cycle often more than 20 m thick and overlying minor cycles that are usuallyless than 6 m thick. Each of the cycles, both initial and minor, are coarsening upwards sequences from marine limestone or mudstohe to deltaic and fluvial mudstone, sandstone, seatearth and occasionally a thin coal seam. The underlying Asbian consists of seven cyclothems averaging 8 m thick. By contrast they are simple coarsening upwards sequences similar to the Brigantian initial cycles, but no minor cycles are developed.Marine fossils are abundant in the majority of cyclothems and are listed against their stratigraphical horizon in the borehole. Special studies of miospores, conodonts and foraminiferans from the borehole are presented. A consensus of biostratigraphical evidence shows that the base of the Carboniferous succession in the borehole is of early Asbian age.

Biostratigraphic zonation and correlation of Mississippian rocks in Western Europe: some case studies in the late Viséan/Serpukhovian

“…Similarly, concavus stage forms of archaediscids which first appear in the Holkerian, survive through to the Arnsbergian (late Serpukhovian) and overlap with tenuis forms, for example in the Grindstone Limestone in the Woodlands Borehole, Alston Block, N. England (Cózar and Somerville, unpublished data) and overlap substantially with angulatus stage forms in the Asbian (e.g. White in Johnson and Nudds 1996). However, as involutus, concavus and angulatus stages are part of an evolving lineage it is quite inappropriate to use them as precise biostratigraphic markers to define the base of the Arundian, Holkerian and Asbian substages, respectively.…”

“…Many of the limestones in cyclothemic sequences (e.g. Yoredale facies in northern England and the Midland Valley of Scotland) contain distinctive macro-and microfossil assemblages which can be used for biostratigraphic correlation between platforms and basins (Holliday et al 1975;Burgess and Mitchell 1976;Johnson and Nudds 1996;Cózar and Somerville 2004). The limestone component of siliciclastic-dominated cyclothems usually represents the initial transgressive phase of the cycle (TST) when there is widespread carbonate sedimentation with attendant new biota.…”

“…For instance, it is now recognized that involutus stage forms persist from the Arundian (lower Viséan) through to the Asbian (Upper Viséan) and overlap in time with concavus stage forms (cf. White in Johnson and Nudds 1996;Somerville 2004, 2005a). Moreover, taxa such as Planoarchaediscus are known to extend into the Serpukhovian (Vdovenko 2001;Cózar 2005).…”

“…Moreover, although there are several studies in which algal genera are occasionally documented (e.g. Hallett 1971;Conil et al 1980;Somerville and Strank 1984;Somerville et al 1992aSomerville et al , 1992bSomerville et al , 1992cJohnson and Nudds 1996;Gallagher and Somerville 1997), they do not provide any additional data on their biostratigraphical range. Of special interest are the works of Mamet and Roux (1974, 1975a, 1975b, 1977 and Mamet (1991), who revised many Carboniferous calcareous algal genera, and described new genera and species, as well as documenting numerous stratigraphic ranges and palaeogeographic distribution of algal taxa.…”

“…There is a need for better integration of biozones using different faunal and floral groups in combination, for example foraminiferans, conodonts and miospores. This can be readily achieved when successions contain alternations of carbonates and siliciclastics in marginal marine and nearshore sequences, for example in Northern England (Johnson and Nudds 1996;Cózar and Somerville 2004); Midland Valley of Scotland (Neves et al 1973;Neves and Ioannides, 1974;Dean 1987), NW and NE Ireland (Somerville et al 2001;, NW Germany and Poland (Skompski 1996;Matyja et al 2000), and the Russian Platform (Makhlina et al 1993;Makhlina 1996). 3.…”