The debate concerning the origin of the Whin Sill of northeast England during the early and mid-19th century

The term sill nowadays employed for a broadly concordant igneous intrusion is widely believed to have been derived from the local term for persistent hard beds in the Carboniferous sequence of Northeast England, in particular the Whin Sill. Despite the intrusive origin of the Whin having been demonstrated in Teesdale by Sedgwick in 1827, for much of the 19th Century the alternative extrusive hypothesis, of which Phillips (1836) was the principal proponent, was widely favoured. There were three principal reasons why the intrusive origin was not more widely held, unquestioning acceptance of the erroneous belief of local miners that the Whin Sill was always at the same stratigraphical horizon, a perception that the Teesdale outcrops were not necessarily typical of the rest of the region and a reluctance to accept that the intrusion of such large volumes of magma over such a great area was physically possible. In the 1870s, first the work of Tate and then the detailed six-inch to one-mile mapping of the Geological Survey finally dispelled any notion that the sill was at a consistent stratigraphical level. Curiously, though the correct determination of the intrusive origin of the Whin Sill was one of Sedgwick's earliest and greatest achievements in Northern England, it was not deemed of sufficient importance to merit mention by his biographers.

The Market Weighton High in the 21st century – new understandings of a long standing problem

The sequence of Jurassic and Cretaceous strata laid down in north Lincolnshire is traced northwards onto the Market Weighton High, and compared with the equivalent Cleveland Basin sequence as it is traced south onto the High. Understanding of the manner of operation of the High has long been hindered by the amount of erosion of strata over the High, particularly in the Early Cretaceous. Facies analysis of the remaining strata present on either side of the High is used to estimate the thickness and the facies of strata originally deposited over the High. Although there were periodic uplifts of the High, leading to increasing omissions of strata approaching the High, there is little evidence that during the Jurassic the High was emergent for significant periods. Most strata were either originally present at Market Weighton in marginal marine facies, or continued across the High without interruption. The operation of the High in the light of modern understanding of crustal stresses during the Mesozoic is reviewed.

A bored cup of the Mississippian crinoid Synbathocrinus Phillips

Only the second bored cup of the disparid crinoid Synbathocrinus conicus Phillips is described, infested by a pit of Oichnus paraboloides Bromley. Both bored specimens are from the Mississippian of Salthill Quarry, Clitheroe, Lancashire, UK, although the search for others has extended from northern Europe to North America. The first, described 30 years ago, infested a plate triple-junction of the cup on the presumed up-current side of the crinoid; the new specimen, in contrast, is in the centre of a radial plate, which is inflated as a growth response to infestation. We informally name the producing organism the ‘Salthill bug’. Although unknown, this was a small, unmineralized invertebrate that commonly attached to elevated positions on living crinoids and was likely a filter feeder. It constructed a domicile by boring into the crinoid endoskeleton, and could invade both living and dead crinoid skeletons. On crinoid stems it was commonly gregarious, a habit perhaps favoured by secretions by the first ‘Salthill bug’ to settle, attracting conspecific larvae and similar to the settling patterns of some modern sessile invertebrates. Comparison with Oichnus from Trearne Quarry, Ayrshire, UK, reveals several differences between the pits in infested crinoids at the two sites.

The palynology of the Kimmeridge Clay and Carstone formations (Upper Jurassic – Lower Cretaceous) at Middlegate Quarry, North Lincolnshire, UK, and its biostratigraphical and palaeoenvironmental significance

At Middlegate Quarry, the Carstone Formation is an approximately 0.8 m thick unit of oolitic ferruginous sandstone. It rests unconformably on the lower Kimmeridge Clay Formation (KCF) and is overlain by the Hunstanton Formation (Red Chalk) with an apparently gradational junction. Marine dinoflagellate cysts (dinocysts) are present at a concentration of 9,520 to 13,600 specimens per gramme in the 0.15 m of KCF below the unconformity, and include taxa that confirm ammonite evidence for the intra-Lower Kimmeridgian Substage (Upper Jurassic, Cymodoce Ammonite Zone). A rich recovery of well-preserved Lower Cretaceous palynomorphs is reported for the first time from the overlying Carstone. Reworking of mudstone from the KCF into the formation appears to have provided a local argillaceous preservation matrix at Middlegate. The basal 0.15 m is dominated by palynomorphs derived from the KCF but the interval from 0.15 m to 0.55 m above the unconformity mainly contains indigenous Lower Cretaceous palynomorphs. Dinoflagellate cysts are present in the Carstone at an average concentration of 454 specimens per gramme, and include taxa that probably have stratigraphical range bases above the Aptian – Albian stage boundary; Cyclonephelium compactum, Cyclonephelium intonsum, Endoscrinium heikeae, Leptodinium cancellatum (consistent), Stephodinium coronatum and Stephodinium spinulosum. The additional presence of taxa with range tops / event tops in the Lower Albian Tardefurcata Ammonite Zone (common Cauca parva, frequent Canninginopsis monile and Kleithriasphaeridium eoinodes, and rare Dingodinium albertii, Discorsia nannus and Kiokansium prolatum) indicate probable assignment to this zone. The new palynological data support previous macrofossil (brachiopod) study of the Carstone at Middlegate and nearby Melton Bottom Quarry which tentatively assigns its highest part to the Tardefurcata Zone. The palynological and palynofacies assemblages are interpreted to confirm a relatively proximal to shoreline site of deposition, possibly inner to middle neritic.Supplementary material: One pdf file, with quarry photographs and a palynological distribution chart, is available at https://doi.org/10.6084/m9.figshare.c.5538977

Bituminous coals on emergent surfaces in an Asbian, lower Carboniferous (Mississippian) limestone succession on the North Wales carbonate platform, UK, and implications for palaeoclimate

Emergent surfaces in the Mississippian (Asbian to Brigantian) carbonate platform succession of North Wales record periods of plant colonisation and peat formation that led ultimately to the local development of coals. Examination of bituminous coals on three emergent surfaces within Cefn Mawr Quarry reveals information on palaeoclimate that is not available from study of the limestones alone. Three coal seams in the Asbian Loggerheads Limestone Formation were identified and the lowest one studied in detail. Vitrinite reflectance data from alternating bands of vitrite and duroclarite microlithotypes, the distribution of pyrite within them, and the sharp contacts between them, suggest that there were abrupt changes in marine influence during the development of the peats that formed the coals. It is inferred that local palaeoclimate alternated between periods of high and low rainfall, the amount of rainfall influencing the extent to which seawater encroached into the peats, with higher rainfall suppressing the ingress of saline waters into groundwater. On the basis of modern peat growth rates, the timescale of the alternation indicated by each duroclarite-vitrite couplet is suggestive of an annual cycle, such as would arise in a monsoonal climate. The low proportion of ash in the three coals, the preservation of internal lamination, the low diversity of spore species in the lowest coal compared with the over- and underlying mudrock, and the presence of rhizoconcretions in palaeokarstic limestone beneath the lowest and highest coals, demonstrate that the peat swamps were isolated from the hinterland and autochthonous. This study demonstrates that a wider application of palynology and coal petrology is an important contribution to the study of marine carbonate successions of any age where terrestrial organic matter, formed during emergence, has been preserved.

The stratigraphy of the Kimmeridge Clay Formation (Jurassic) of the Vale of Pickering, Yorkshire, UK

The Upper Jurassic Kimmeridge Clay Formation (KCF) underlies much of the Vale of Pickering where it is almost wholly concealed by the Cretaceous Speeton Clay and Quaternary deposits. There are few KCF inland or coastal exposures in Yorkshire with the result that the succession was stratigraphically poorly known until the 1970s oil crisis when the British Geological Survey (BGS) drilled continuously-cored boreholes at Marton and Reighton to examine the formation as a possible source of hydrocarbons. These were supplemented in 1987 by continuously-cored boreholes drilled at Marton, Reighton, Ebberston and Flixborough by the Institut Français du Pétrole (IFP) for hydrocarbons research. Taken together, the boreholes have enabled the lithological, palaeontological, geochemical and geophysical characters of the full thickness of the formation to be examined. Comparison of the KCF successions proved in Yorkshire with those in the adjacent North Sea, the East Midlands and the Dorset coast type area, shows marked variations in thickness related to penecontemporaneous faulting. However, there are only minor variations in the lithologies and faunas at any particular stratigraphical level. This appears to be due to a combination of Milankovitch-driven climatic fluctuations and pulsed variations in sea level which combined to produce similar depositional conditions throughout the English KCF at any one time. The chronostratigraphical classification of the KCF developed in southern England has therefore been shown to be applicable to the Yorkshire outcrop and the southern North Sea. The changes in sea level may be eustatic rather than regional events, but there is insufficient paleontological evidence to enable them to be correlated with confidence with those of the standard Jurassic sea-level curve.

Reappraisal of Arundian–Asbian successions of the Great Scar Limestone Group across northern England

The correlation of disparate mid- to late Viséan platform carbonate successions of the Great Scar Limestone Group across northern England formerly relied heavily upon a coral and brachiopod biozonation scheme erected in the early 20th century. This subsequently guided the development of a regional chronostratigraphic scheme some sixty years later that continues to be used to the present day, broadly coinciding with development of new lithostratigraphical nomenclatures, different for each distinct structural area. Correlation problems encountered within these lithostratigraphic units from study of their foraminiferal assemblages, as well as critical analysis of the stratotype sections for the Holkerian and Asbian substages, questions the veracity of the long-established coral and brachiopod biostratigraphy. This study appraises the lithostratigraphical and biostratigraphical relationships of late Arundian to late Asbian limestones across the Askrigg and Alston blocks, the Stainmore Trough and flanks of the Lake District Block. It considers the correlation and potential rationalisation of lithostratigraphic units, comments on revisions to the definition of the Holkerian and Asbian substage stratotypes and the suitability of the various biostratigraphical guide fossils.

Fast post-mortem encrustation of razor shells: examples from the Irish Sea and palaeontological implications

Instructive taphonomic principles are demonstrated by the skeletons of dead invertebrates. Bivalves have resistant skeletons and are common fossils. The thin-valved razor shells, Ensis spp., have a good fossil record despite being fragile. This may be due, in part, to rapid post-mortem encrustation of valves by mineralized invertebrates. Two Recent specimens of Ensis siliqua (Linnaeus), encrusted post-mortem, are described from the Irish Sea coast of Southport, Merseyside. An articulated shell with an intact ligament is encrusted posteriorly on all surfaces by the balanid Balanus crenatus Brugiére. Barnacles inside the shell are smaller than those externally, yet may represent the same spatfall; those inside were constrained by growing in an enclosed space. To a palaeontologist, a mollusc valve encrusted inside and out by cementing organisms would be interpreted as having had a long residence time on the seafloor. This specimen demonstrates the disjunction between loss of soft tissues (days?) and loss of the ligament (weeks, perhaps months), between which encrusters may settle inside the shell, early in its post-mortem history. Similar patterns of encrustation by balanids are now known two species of Ensis and the cockle Cerastoderma edule (Linnaeus).A fragment of a single valve is encrusted only on the internal surface by serpulids and bryozoans. This is balanulith-like, but is only encrusted on the inner surface and not by balanids. Ensis valves can be reinforced by a range of calcareous encrusting organisms; an Ensis fragment encrusted both inside and out by serpulids would be worthy of being named a serpulith.