Journal ofthe Geological Society, London, Vol. 148, 1991, pp. 379-390, 7 figs. 1 table. Printed in Northern Ireland The Lower Carboniferous Stainmore Basin, N. England: extensional basin tectonics and sedimentation R. E. L1. COLLIER Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK Abstra& Recently released industry seismic data image a 6 km thick Dinantian succession in the Stainmore Basin, and are used to interpret deposition in response to extensional subsidence. The basinis bounded to the north by the Lunedale-Wigglesworth-Butterknowle enechelon suite of normal faults. An early (?Courceyan-?Arundian) syn-rift sequence more than 4 km thick includes footwall-derivedclastic fans. A basinalterrigenous sequence deposited through the Arundian, Holkerian and early Asbian contrasts with coeval carbonates on the Ravenstonedale Shelf and the Askrigg Block. Deposition continued in the basin whilst the Alston block and northern parts of the basin were emergent during early Asbian times. A late Asbian relative base level rise and the possible cessation of active rifting allowed both basin and structural highs to be inundated by shallow marine carbonates. Rhythmic ‘Yoredale’ sedimentation followed. Dinantian depositional patterns reflect the interplay between active extensional faulting, a susp- ected local inversion event, changes in sediment influx rates, sea level variations and differential rates ofcompaction between basement highs and the basin. However, error marginson the available biostratigraphy and timing of active faulting prevent the detailed separation of these variables and their impact on sedimentation in the Dinantian. The Stainmore Basin forms one of a number of NE-SW to the contrasts in sedimentary facies around the basin to be E-W trending sedimentary basins in northern Britain that established for much of the Dinantian. A model has been formed in response to lithospheric extension in the Lower constructed of three-dimensional facies variation in response Carboniferous(Dewey 1982; Leeder 1982, 1987~).The to rifting. The significance of establishing the areal regional tectonic context of the basins has been related by dimension is that areal variance in facies is to be expected these authors to crustal stretching (in a back-arc position) to around the margins of any rift basin, in accordance with the thenorth of the Rheno-Hercynian collisional zone.An differences in fault activity around the margins of the basin. easterly structural tilt across Stianmore exposes lower parts Three further themes are introduced, the first of which of the Carboniferous succession in the west of the basin. In arises out of the inferredrelationship between facies theeast, Silesian depositssubcrop the base-Permian patterns and rift histories. This explores the degree to which unconformity in thearea (Fig. 1). Footwall highs tothe sedimentary featuresand sequencegeometries within an north and south of the basin comprise relatively low density overall rift ‘megasequence’ can be used to distinguish more basement blocks buoyed by the Weardale and Wensleydale detailed pulses of rift activity from ‘passive’ infilling phases granites respectively (Dunham et al. 1965; Bott 1967; Wilson when subsidencecontinues dueto lithoshperic cooling & Cornwell 1982). (McKenzie 1978). Despite this problem,the secondpoint Recent work hasled theto characterization of emphasizes that seismic facies analysis within a depositional sedimentary facies patterns expectedin active rift basins sequenceframework, and constrained by well andtor (e.g. Leeder & Gawthorpe 1987; Dodd & Gawthorpe 1991). outcrop data, can improve the interpretation of a basin fill This has led to the process of deriving information about a andits tectonic significance. The third theme is the basin’s rift history fromthe sedimentary fill. Such an distangling of threethe variables of tectonic approach isnow being applied to Carboniferous basins in subsidenceJuplift rates, rates of eustatic sea level changes Britain, and sedimentary and sequence geometries related and sediment supply rates, which can then beaddressed to active faultinghave been described by Williams et al. within the depositional sequence framework. (1989) in the Munster and South Munster Basins, Wilson et Previous work (Bott 1967; Burgess & Mitchell 1976; al. (1988) in the SE Wales area, Ebdon et al. (1990) in the Burgess & Holliday 1979; Dunham & Wilson 1985) based East Midlands, Gawthorpe (1986) in the Bowland Basin and on gravity, outcrop studies and shallow boreholes,has Ord et al. (1988) in the Solway Basin. This paper follows a established thatthe Stainmore Basin had an extensional similar approach in relation to the Lower Carboniferous of half-graben or asymmetric graben morphology during the the StainmoreBasin, inferring details of its rift evolution Lower Carboniferous, being one of anumber of such from the character and variation in basin-fill deposits. The Carboniferousstructures in northern Britain (reviewed in study has used newly available seismic data tied to well logs Gawthorpe et al. 1989). The principal structural elements of and outcrop, to extend our understanding of the Stainmore the basin are outlined on Fig. 1. The basin is inferred to be succession. an asymmetric graben with its major bounding structures in 300 km of seismic sections from the north-central area of thenorth, the en echelonLunedale, Wigglesworth and Stainmore (Fig. l), together with outcropto the north, ButterknowleFaults (Fig. 2). Thesouthern basin margin south and west, supported by borehole data, have allowed must befault-bounded, probably along the line of the 379 Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/148/2/379/4891699/gsjgs.148.2.0379.pdf by guest on 02 October 2021 a \ Permian-Mesozoic Carboniferous: --- Westphalian ......... Namurian AlstonGroup ...... m H...... Dinantian Lower .-. 'I' Basin-bounding Palaeozoics normalfault Fault 7Thrust fault Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/148/2/379/4891699/gsjgs.148.2.0379.pdf by guest on 02 October 2021 LO W ER CARBONIFEROUS,LOWER STAINMOREBASIN 381 a NORTH 0 1 km SOUTH b U Fig. 2. (a) Migrated seismic section across the northern marginof the Stainmore Basin from the UK86 survey. (b) Structural and depositional sequence interpretation of the seismic line in (a). Numbers 1-6 denote depositional se- quences within the Lower Carboniferous basin-fill. Lithostratigraphic divisions are approximate equivalents of these deposi- tional sequences.'A highlights clino- forms in depositional sequence1. Approximate depth scale is converted from seismic stacking velocities. LA-6000 Stockdale Disturbance, because the northwardsextrapola- faults and occurrences of syn-sedimentary deformation. tion of sedimentarydips onthe Askrigg Block does not Both lines of evidence are used to constrain- the timing of accommodate the thickness of Dinantian sediment imaged on syn-rift fault movements, the latter after Leeder (19876). the seismic to the north. At the western end of Stainmore, the succession exposedin the Ravenstonedale area is Stratigraphic evidence around the basin margins interpreted as a shelf sequence, starved of the clastic material that dominated deposition in the basin proper for Alston Block much of theDinantian, as discussed below. Critical The Lower Carboniferous succession on the Alston Block is relationshipsstudied in the field include facies and well documented dueto its widespreadexposure (e.g. sedimentary thickness changesacross surface outcrops of Burgess & Holliday 1979) and its penetration by a number Fig. 1. (a) Location map for the Stainmore Basin, onshore north-east England. Open circles indicate boreholes and filled circles wells that were used to constrain seismic interpretation and stratigraphies. 1, Brafferton-l; 2, Seal Sandsno. 1; 3, Rookhope; 4, Collier's Law; 5, Roddymore; 6, Woodland; 7, New Shildon no. 146; 8, Randolph; 9, Mount Pleasant; 10, Coldsides; 11, Beckermonds Scar;12, Raydale. Detail (b) outlines structures at the western endof the Stainmore Basin.A and B locate sections logged and illustrated in Figure3. Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/148/2/379/4891699/gsjgs.148.2.0379.pdf by guest on 02 October 2021 382 R. E. L1. COLLIER Table 1. Stratigraphic correlation between the Lower Carboniferous of the Stainmore Basin and surrounding areas ~~~~ ~~~ ~ ~ RAVENSTONEDALE 4SKRIGGBLOCK Stage ALSTONBLOCK STAINMOREBASIN SHELF (Northernarea) P P a a BRIGANTIAN 0 2 L 0 0 C C 0 0 c c -U) -U) 4 4 DannyBridge GreatScar KnipeScar Limestone I - Limestone Limestone ASBIAN PottsBeck Garsdale Limestone Limestone Ashfell Fawes Wood Hillbeck HOLKERIAN Hillbeck Limestone Limestone Limestone Limestones P Formation a a a ~~ 2 2 Ashfell 0 0 Ashfell Ashfell Sandstones C C Sandstone Sandstone 0 \ Ashfell 0 c c L L taven avenstonedalc 0 \ 0 TomCroft Limestone Limestones Formation / -- 301./Sst.' CHADIAN D .- I RomanFell Beds 1 Sandstones P P m a a 0 0 Tebay L L I0 0 Conglomerates RomanFell c c C c ! m m Shales E I m COURCEYAN U) PinskeyGill m m m m Beds Basal Congloms. LL Sources include Barraclough (1983), George et al. (1976), Burgess & Holliday (1979), Higgins & Varker (1982), Strank (1982) and Wilson & Cornwell (1982). of boreholes (Woolacott 1923; Dunham et al. 1965). Here Sandstones may have extended into the HolkerianI (Higgins the pre-Arundian Dinantian succession (Table 1) is limited & Varker 1982). to 50-200 m in thickness. The petrographic content of basal The overlying Holkerian Hillbeck