.I.micropalaeontol., 2: 13 -- 16, July 1983

:Basal Dinantian miospores from the area, West

M. A. BUTTERWORTH & C. E. BUTCHER Depdrtment of Geologic,al Sciences, University of Aston, Birmingham B4 7ET & 27 Levinson Crescent, Balsall Common, Warwickshire

.4BSTRACT--Miospore assemblages arc described from basal Dinantian argillaceous strata lying below and above the Cockermouth Lavas, and within the Seventh Limestone in the area to the north east of Cockermouth, West Cumbria. The strata enclosing the Lavas are assigned to the Schopfites claviger-Auroraspora macra miospore zone, indicating the Ivorian stage (Tournaisian, Tn3). The Lavas are thus shown to be of similar age to the Solway Plateau Lavas to the north which represent an early stage in the formation of the Solway Basin. Shales from below the Seventh Limestone are assigned to the Lycospora pusilla miospore zone and from this and other fossil evidence are presumed to be of Chadian or early Arundian age. Shales from within the Seventh Limestone are assigned to the Perotrilites tessellatus - Schulzospora campyloptera miospore zone ( Asbian stage) It is concluded that the Ivorian-Asbian sequence in this area is greatly attenuated com- pared with its development on the northern margin of the Solway Basin.

INTRODUCTION Miospore assemblages have been examined from the stone, and there is a brief description by Eastwood et al. Basement Conglomerate and from strata above the (loc. cit.) who record a shelly fauna in the uppermost Cockermouth Lavas and associated with the Seventh shales. The 20 metres or so of exposed strata comprise Limestone in the area of West Cumbria lying to the mudstones with occasional shales and with three harder nortlh east of Cockermouth, on the northern flanks of the horizons of calcite mudstone containing Modiolus and (Fig. 1). ostracods, and forming small waterfalls. The highest cal- 'The strata (c. 30 metres) below the iavas are termed cite mudstone horizon is overlain by a metre of limestone the E{asemient Conglomerate (Eastwood et al., 1968) and breccia with quartz pebbles which makes a convenient lie with marked unconformity on the Slates. marker horizon. The), are well exposed in Tommy Gill, Redmain (Grid The earliest diagnostic fossils recorded in these Ref.: NY 138335). The Cockermouth Lavas die out Dinantian strata are the brachiopods and corals occurring eastwards and in the and Fellside areas the Base- in black shales immediately below the Seventh Lime- men1 Conglomerate lies unconformably on Eycott stone and in the limestone itself. According to Eastwood Lavas and is thicker, but seldom exposed. In both areas el ul. (1968, pp. 160-161) these indicate the it consists of coarse conglomerates interbedded with Nemutophyllum minus (S2) zone and fossils normally grits, sandstones and mudstones, ranging in colour from restricted to the LowerDibunophyllumZone (D1) occur grey-green to yellow and red, and sometimes with a at the top of the Seventh Limestone. George et al. calcareous cement. (1976) assign the Seventh Limestone to the Holkerian The Cockermouth Lavas, olivine basalts of Dalmeny stage because of the presence of the characteristic type, reach up to 100 metres in thickness. They overlie Holkerian brachiopod Davidsonina carbonaria which the unfossiliferous Basement Conglomerate and are Eastwood et al. record near its base. The Cockermouth succeeded by about 20 metres of interbedded shales, Lavas and the unfossiliferous Basement Conglomerate limestones, and calcite mudstones which, together with are assumed to be of Arundian age by George et al. (1976, the overlying Seventh and succeeding limestones, are Fig. 11; in Table I1 the higher part of the Cockermouth assig:ned to the Lower Chief Limestone Group Lavas is included in the Holkerian stage.) (Easfwooci et ul., loc. cit.). These strata crop out in Gill Mitchell (1978, p. 173) states that corals recorded by Beck (NY 149345), south of the Ghyll Yeat Inn in earlier workers from low horizons in the Seventh Lime- , which drains southwards into the River stone at Beckermet to the south west and Berrier to the Derwent. Shackleton (1973), Butcher (1974) and Welsh east of the present area are now identified as the late (1980) give details ot the section between the Chadian - early Arundian species Thysanophyllum Cockermouth Laws and the base of the Seventh Lime- pseudovermiculare ; they are associated with typical

13 Butterworth & Butcher

Fig.1. Map of sampling locations 1 based on Geological Survey Sheet 23, Cockermouthi

Arundian archaediscids. Mitchell believes that the (ii) 2 metres dark grey shales from near to the base of shallow water conditions present in the lower parts of the Lower Chief Limestone Group, lying about 7 the Seventh Limestone may, therefore, represent the metres (strata unexposed) above the top of the regressive part of the Arundian mesothem ; the beds Cockermouth Lavas in Gill Beck, Blindcrake. containing L)uvid.c.oninucurhonuriu would be deposited (NY 14Y345) during the following Holkerian transgression and (iii) 2 metres fossiliferous grey shales from higher in Mitchell (loc. cit., p. 174) notes that the restricted the Lower Chief Limestone Group, lying above environment of the area during this time is indicated by the limestone breccia and below the massive part the lack of diversity in the faunas and by the records of the Seventh Limestone at the top of the Gill of anhydrite etc. in the Seventh Limestone of the Beck section. (NY 149346) Egremont area to the south west (Llewcllyn et. ul., (iv) Carbonaceous band in the 6 metre limestone se- I06X). quence exposed in an old quarry (NY 124327) near to Wood Hall. This is part of the Seventh MAT ERIA L STU DI ED Limestone which is faulted against the Cocker- Six wmples yielded reasonable miospore separations mouth Lavas and which lies an unknown distance when macerated by standard procedures, i.e. removal of above the Gill Beck sequence. carbonates and silicates by hydrochloric and hydrofluoric (v) 10 cm black shales with occasional bryozoans acids and oxidation of the organic residues with fuming interbedded with limestones in the left bank of nitric acid. Park End Beck. (NY 297385) (i) 3Ocm grey mudstone underlain and overlain by (vi) hl cm black shales rich in bryozoans interbedded red marls in the right bank of the stream with very fossiliferous limestones in the left bank at approximately 600 metres due south of the of Park End Beck. (NY 298385) village of Uldale. Similar sediments were sampled Samples (v) and (vi) are from the Bryozoa Band which at two points along the stream bank approximately occurs towards the top of the Seventh Limestone 25 metres apart; these yielded comparable (Eastwood rt ul., 1968, p. 172). miospore 2issemblages and probably represent Samples of fine-grained sediments in the Basement thc same horizon in the Bascrncnt Conglomerate. Conglomerate directly underlying the Cockermouth (N Y 25 13h6) l>avasin l’ommy Gill, Kedmain were non-productive.

14 Dinantian miospores from 'West Curnbria

MIOSPORE ASSEMBLAGES concluded therefore that all of the Seventh Limestone N~esel al. (1972) defined eight concurrent range samples in the present study (iv, v and vi) are from the zones based on miospore distributions in the British TC~-~- rone,~ Dinantian, and five of these were recognised in the Midland Valley of Scotland and in northern THE AGES OF THE MIOSPORE ASSEMBLAGES In their survey of Dinantian strata in Britain, George by Neveset a1 (1973). Clayton (1977) modified the et al. et ul. (1 976, Table I) indicate the relationships between limits of the zones and applied them to western Europe their stages and the miospore zones of Neves ei al. (1972). generally. Further modifications (Clayton 1978) et al., Ramsbottom & Mitchell (1980) suggest that the lowest followed from comparative studies of miospore, (Courceyan) stage should be replaced by the Belgian conodont and foraminifera1 distributions in the British Hastarian and Ivorian stages, representing lower (Tn 1b Isles and the Ardennes. pars and Tn2) and upper (Tn3) parts of the Tournaisian Thie samples from the Basement Conglomerate (i) series respectively; in their Table I the CM zone falls and the lowest part of the Lower Chief Limestone within the Ivorian stage and the base of the Pu zone Group (ii) contain miospore assemblages dominated by coincides with the base of the Chadian stage and the base spp. and with significant numbers of Punctatisporites of the Visean series. George et al. (loc.cit.) and Clayton Retusotriletes incohatus Sullivan, Crassispora trychere et al. (1978) indicate that the Pu zone extends through Nevt:s & Ioannides and Sullivan ; the Schopfites claviger the Chadian, Arundian and Holkerian stages with the presence of the last two species together with the overlying TC zone having a common base with the absence spp. indicates that the samples are oSLycospora Asbian stage. almost certainly of Schopfites claviger - Auroraspora It follows from the present investigations, therefore, macra (CM) zone age. Other species present include that the CM zone samples from the Basement Con- Rugospora polyptycha Neves & Ioannides, Colatisporites glomerate (i) and from just above the Cockermouth Ve n k a t acha1 a) Wi I I i a m s, deco ,'us (Bh aradwa j & Lavas (ii) arc Ivorian in age. The Pu zone sample (iii) Grarzdispora echinata Hacquebard and A.mucra Sullivan. from above the limestone breccia in Gill Beck could be The higher assemblage (ii) contains a more diverse of any age from Chadian to Holkerian. I i n c 1u d i n g u n itidus m i c r o f 1 o a Ver r c 0s ispo rites The presence of high numbers of Prolycospora (Naumova) Playford, spp., Convolutispora Pulvinisporu rugulosa does not help to shorten this possible range; quusrlabruta Higgs, P. scokcophora Neves &: Ioannides similar abundances are present in black shales sampled and Spelaeotrilete,s pretiosus (Playford) Neves & Belt. in Tarras Water, Langholm, from the highest part of the The assemblage yielded by the shales above the lime- Lower Border Group (M.A.B., unpublished data) which stone breccia in Gill Beck (iii) differs from those of George et al. (1976) assign to the upper part of the samples (i;) and (ii) in the absence of most of the species Courceyan stage (Ivorian stage of Ramsbottom & listed above and in the presence of high riumbers of Mitchell, 1980), and Butterworth & Spinner (1967) Proljcospora rugulosa (Butterworth & Spinner) Turnau record high numbers from horizons in the Chadian and and some Lycospora noct,uina Butterworth & Williams Holkerian stages in addition to the Lewisburn type and 1,. (Ibrahim) Somers. It is concluded that this pusilla locality of presumed Asbian age. P. rugulosa thus has a horizon lies in the Lycosporu pusilla (Pu) zone as long stratigraphic range and its local abundance must be intensive searching yielded no evidence of (hssispora due to unknown ecological factors. uculeatu Neville, Schulzospora spp. or Perotrilites The TC zone sample (iv), (v) and (vi), from shales tes.sel1atu.s (Staph) Nevilllc which characterise the over- within the Seventh Limestone, have miospore assem- lying P. tessellatus - S. campyloptera (TC) zone. blages consistent with an Asbian age. The prlesence of abundant lycospores, common densmpores, Schulzospora campylopteru (Waltz) DISCUSSION Potonie & Kremp and Dictyotriletes plumosus Butter- The miospore assemblages recorded from the Base- worth & Spinner in sample (iv) from Wood Hall, probably ment Conglomerate and the lower part of the Lower in the lower part of the Seventh Limestone, indicates the Chief Limestone Group suggest that these strata, and TC zone. !Samples (v) and (vi) from the Bryozoa Band the included Cockermouth lavas, are older than the in Park End Beck, higher in the Seventh Limestone Arundian age previously suggested (George et al., sequence, yielded similar but less varied assemblages; 1976). They are of a similar (Ivorian) age to other basal Pro1.ycospora rugulosa is common in the lower of the two Carboniferous strata flanking the Lake District and Triquitrites cornptus Williams appears in the higher (Holliday, Neves & Owens, 1979; Welsh, 1980). sample. CRayton et ul. (1977) indicate that Triquitrites The Cockermouth Lavas are of similar type to the spp. make their first appearance in the Raistrickia nigra - Kelso Traps of the Tweed Basin and to the Birrenswark Triquitrites murginutus (N M) zone but Williams (in Lavas of Dumfriesshire which George et al. (loc. cit.) Neves et ul., 1973) records T. cornptus from lower state to be middle low Courceyan in age; they could horizons, in the TC zone of the Brampton area. It is therefore form a part of the Solway Plateau Lavas

15 Butterworth & Butcher postulated by Cieikie (1897) and later believed by REFERENCES Leeder (1974) to represent an early stage in the for- Butcher, C.E. 1974. Carboniferous miospore distributions in mation of the Solway Basin. with special reference to those in the Hensing- ham Group. Unpublished Ph.D. thesis, University of Aston. The Pu zone assemblage recorded from the black Butterworth, M.A. & Spinner, E. 1967. Lower Carboniferous shales (iii) above the limestone breccia in Gill Beck spores from north-west England. Palaeontology, , could be from the Chadian, Arundian or Holkerian 10, 1-24. stages. However, the presence of the late Chadian - early Clayton, G., Coquel, R., Doubinger, J., Gueinn, K. J.. Loboziak, Arundian coral Thysanophyllum pseudovermiculare S., Owens, B. & Streel, M. 1977. Carboniferousmiosporesof and Arundian archaediscid foraminifera recorded at Western Europe: illustration and zonation. Meded. Rijks similar or slightly higher horizons elsewhere in the area Geol. Dienst., Leiden, 29, 1-71. Clayton, G., Higgs, K., Keegan, J.B. & Sevastopulo, G.D. (Mitchell, 1978, 173) suggests that the shales over- p. 1978. Correlation of the palynological zonation of the lying the breccia are of Chadian or early Arundian age. Dinantian of the British Isles. Palinologiu, 1, 137-147. The TC zone (Asbian) age of miospore assemblages Eastwood, T., Hollingworth, S.E., Rose, W.C.C. & Trotter, from black shales within the more massive parts of the F.M. 1968. Geology of the country around Cockermouth Seventh Limestone (samples iv, v and vi) are pre- and . Mem. geol. Surv. U.K. X + 298 pp. sumably from higher horizons than the beds containing Geikie, A. 1897. Theancient volcanoesofGreatBritain. (2 vols.) London. the Holkerian brachiopod Davidsonina carbonaria George, T.N., Johnson, G. A.L., Mitchell, M., Prentice, J.E., which occurs near to its base (George et al., 1976). The Ramsbottom, W.H.C., Sevastopulo, G. D. & Wilson, R.B. age based on miospores is in accord with the presence of 1976. A correlation of Dinantian rocks in the British Isles. D, (Asbian) fossils recorded by Eastwood et ul. (1968) Geol. SOC.Lond., Special Report No. 7, 87 pp. at the top of the Seventh Limestone. Holliday, D.W., Neves, R. & Owens, B. 1979. Stratigraphy and It follows from tlie above that the strata representing palynology of early Dinantian (Carboniferous) strata in shallow boreholes at , Cumbria. the Chadian, Arundian and Holkerian stages in this area Proc. Yorks. pol. Soc., 42, 343-356. are greatly reduced in thickness compared with their Leeder, M. 1974. The origin of the Northumberland Basin. development to the east and north where extensive Scott. J. Geol., Edinburgh, 10, 283-296. sandstone deltas were forming along the northern Llewellyn, P.G., Mahmoud, S.A. & Stabbins, R. 1968. margin of the Solway Basin. Nodular anhydrite in Carboniferous Limestone, Cumberland. Trans. Instn. Min. Metall. (Sect. B: Appl. ACKNOWLEDGEMENTS earth Sci.), London, 77, B18-25. Part of this work was carried out by one of the authors Mitchell, M. 1978. In Moseley, F. (Ed.), The Geology ofthe Luke District. Yorks. geol. Soc. Occasional Publication (C.E.B.) during the tenure of a research studentship in No. 3, 284 pp. the Department of Geological Sciences, University of Neves, R., Gueinn, K.J., Clayton, G., Ioannides, N.S. & Aston. Neville, R.S.A. 1972. A scheme of miospore zones for the British Dinantian. C. R. 7th Congr. Int. Curb. Strat. Geol., Krefeld (1971), 1, 347-353. Neves, R., Gueinn, K.J., Clayton, G., Ioannides, N.S., Neville, R.S. A. & Kruszewska, K. 1973. Palynological correlations within the Lower Carboniferous of Scotland and Northern England. Trans. roy. Soc. Edinb., 69, 23-70. Ramsbottom, W.H.C. & Mitchell, M. 1980. The recognition of the Tournaisian Series in Britain. Jl. geol. Soc. London, 137, 61-63. Shackleton, E.H. 1973. Lakeland Geology. Dalesman Books, Clapham, Yorkshire. Welsh, A. 1980. Stratigraphical palynology of early Dinantian strata in Cumbria. Unpublished Ph.D. thesis, University of Sheffield.

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