M.A.E. Browne

A revised correlation of Carboniferous rocks in the British Isles

The report revises and expands upon the 1976 and 1978 publications for the Dinantian and Silesian, respectively, combining them into a single account of British and Irish Carboniferous stratigraphy. The need to update the two Special Reports reflects the considerable advances in Carboniferous geology over the last 30 years. The report covers developments in international chronostratigraphy and incorporates wholesale reassessments of British lithostratigraphy. A huge volume of biostratigraphical information has been published over recent decades and the report summarizes the key information. Carboniferous rocks have long been of economic importance, but it is the search for hydrocarbons, in its infancy at the time of the previous reports, which has greatly increased our understanding of Carboniferous successions offshore and at depth, particularly in southern and eastern England.

Ostracods from freshwater and brackish environments of the Carboniferous of the Midland Valley of Scotland: the early colonization of terrestrial water bodies

The Mississippian Strathclyde Group of the Midland Valley of Scotland yields some of the earliest non-marine ostracods. The succession records shallow marine, deltaic, estuarine, lagoonal, lacustrine, fluvial and swamp environments representing a series of staging-posts between fully marine and limnetic settings. Macrofossils and ostracods are assigned to marine, marginal marine, brackish and freshwater environments based on their faunal assemblage patterns. Key brackish to freshwater ostracods are Geisina arcuata , Paraparchites circularis n. sp., Shemonaella ornata n. sp. and Silenites sp. A, associated with the bivalves Anthraconaia , Carbonicola , Cardiopteridium , Curvirimula , Naiadites , the microconchid ‘ Spirorbis ’, Spinicaudata and fish. Many Platycopina and Paraparchiticopina ostracods are interpreted as euryhaline, which corresponds with their occurrence in marine to coastal plain water bodies, and supports the ‘estuary effect’ hypothesis of non-marine colonization. The success of non-marine colonization by ostracods was dependent on the intrinsic adaptations of ostracod species to lower salinities, such as new reproductive strategies and the timing of extrinsic mechanisms to drive non-marine colonization, such as sea-level change. The genus Carbonita is the oldest and most common freshwater ostracod, and went on to dominate freshwater environments in the Late Palaeozoic.

Late Devonian–Carboniferous tectonic evolution within the Firth of Forth, Midland Valley; as revealed from 2D seismic reflection data

Synopsis Results of integrated seismic mapping, within the Firth of Forth in the offshore Midland Valley of Scotland, are presented and illustrate aspects of the subsurface structure and tectonic evolution of the Upper Devonian to Carboniferous succession. Evidence for three main phases of tectonic activity has been recognized: (1) Late Devonian to Dinantian fault-controlled subsidence; (2) basin-wide Silesian subsidence, localized inversion and growth folding; (3) Late Silesian dextral transtensional and transpressional strike-slip faulting. During the first phase of tectonic activity, the NNE-trending Mid Forth Fault is interpreted to represent a Late Devonian to Dinantian extensional fault, with a small, mainly Dinantian depocentre developed in the hangingwall block that has subsequently been inverted during Silesian times. A major Late Devonian to Dinantian depocentre also occurs in the hangingwall block of the NE-trending offshore continuation of the Crossgatehall Fault, although it remains unclear whether this mainly Dinantian depocentre was developed during pull-apart as a result of extension or transtensional strike-slip fault movement. The NNE-trending Leven Syncline and Mid Forth Anticline within the hangingwall block of the Mid Forth Fault are interpreted as Silesian synsedimentary growth folds that formed during the second phase of tectonic activity. The peak of this activity occurred during intra-Westphalian B to Westphalian C times. In the third phase, the ENE-trending Inchkeith Fault Zone is interpreted as a Late Silesian transtensional–transpressional strike-slip fault that dextrally offsets the axial trace of the Leven Syncline. Evidence from the Firth of Forth could provide support for regional tectonic models involving mainly dextral strike-slip fault activity during Devonian–Carboniferous times, or mainly sinistral strike-slip during Devonian to Early Carboniferous followed by dextral strike-slip during Late Carboniferous times, for the development of the Upper Devonian and Carboniferous succession. However, the latter model is preferred as it provides the more convincing explanation for our interpretation that the NNE-trending Mid Forth Fault represents a Late Devonian to Dinantian extensional or transtensional fault that was inverted during Silesian times. This inversion may therefore reflect a major change in the regional stress field.

Glasgow, a case study in urban geology

A long history of mining and quarrying in Glasgow has left a legacy of engineering problems. Thematic mapping by the British Geological Survey, which takes account of all the available evidence on the distribution of man-made hazards and relevant geological factors, is assisting local and national planning departments in the preparation of proposals for urban renewal and development. Key features described include: lithology, thickness and generalized engineering properties of the drift deposits; bedrock geology; and undermining, with the emphasis on workings close to rockhead.

Discussion on a revised model for the last deglaciation of eastern Scotland Journal, Vol. 164, 2007, 313–316

J. D. Peacock, M. Armstrong, M. A. E. Browne, N. R. Golledge & M. S. Stoker write: We are unable to support the view of McCabe et al . (2007) that there were significant readvances of the Scottish Ice-sheet at Lunan Bay and near Perth. The authors provide no criteria for readvances of glaciers such as terminal moraines, a second till and/or deforming bed, and rafting and overriding of marine sediments. However, we believe that the four new 14C dates in their table 1 are useful additions to knowledge. The supposed Perth Readvance in the type area . We agree that the till at the base of the Almondbank was produced by advancing ice. However, because such till is widespread in eastern Scotland, its occurrence does not of itself support the concept of a readvance, and none of the criteria noted above are satisfied. Indeed, the only indication of a possible very local readvance in the Perth area is near Moneydie, where a section formerly exposed two tills and highly deformed lacustrine silts (Paterson 1974). This we could attribute to the expected readjustment of ice-streams during retreat. Menzies & Van Der Meer (1998) concluded that the evidence here did not support a major readvance, but rather represented ‘a single winter event’. The package of sediments was described as ‘part of a tectonised, sub-glacial, deforming bed sequence’. In the upper Forth Estuary, near Grangemouth, Sissons & Smith (1965) showed that the Main Perth Shoreline is associated with the eastern limit of a stillstand or readvance of ice, which they correlated with the ‘Perth Readvance’. However, in the Tay–Earn area, the marine limit above the Main Perth Shoreline can be followed almost to Crieff, some 25 km west of Perth, where there are fluvial terraces relating to a sea level at …

Stratigraphic and palaeoenvironmental significance of microbial carbonates in the Asbian Sandy Craig Formation of Fife

Synopsis This study concentrates on Viséan Strathclyde Group microbial carbonates from the eastern Midland Valley of Scotland. In the largely non-marine Sandy Craig and West Lothian Oil-Shale formations persistent lithostratigraphical marker horizons, such as distinct microbial carbonates, are used to aid correlation of sequences where conventional biostratigraphy is limited to the identification of infrequent marine bands. In the newly described Rosyth core, microbial carbonates above the Burdiehouse Limestone are correlated with microbial horizons at Kingswood (Fife) and Inchkeith (Firth of Forth), a correlation supported by the presence of the bivalve Curvirimula scotica. The revised position of the Inchkeith microbial horizon to 20–30 m above the Burdiehouse Limestone contradicts earlier correlations of the Inchkeith sequences with the Burdiehouse Limestone. The microbial carbonates represent littoral and sublittoral zone stromatolites growing in <20 m of water. The best modern analogues are stromatolites forming in East African Rift Valley lakes. These microbial carbonates formed in volcanically isolated shallow sub-basins or in association with delta progradation. Lavas and tuffs provided stable substrates free of clastic sediment for stromatolite nucleation, and their weathering may have enhanced Ca2+ ion activity to promote carbonate precipitation. These lacustrine microbial carbonates cannot be implicitly linked with climatic events or basin-wide regression as has been proposed for a regionally persistent microbial carbonate below the Burdiehouse Limestone.

Blocks of marine clay in till near Helensburgh, Strathclyde

Synopsis An occurrence of till containing two large blocks of shelly marine clay is described. Radiocarbon dates on shells from the smaller block suggest that the till formed during the Loch Lomond Stade, although the locality is outside the conspicuous terminal moraine of the Loch Lomond glacier. The origin of the till is discussed.

The physical geography and geology of the estuary and Firth of Forth, Scotland

The Upper Palaeozoic bedrock, which is of sedimentary and volcanic origin, is briefly described. The origin of the Forth as a series of depressions in the bedrock surface probably owes much to erosion of a pre-existing Tertiary landscape during phases of Quaternary glaciation. The late Quaternary history of the area is described, relating the distribution of the sediments deposited in the Forth to climatic events and changes in relative sea-level. Since the acme of the last main glaciation about 20,000 years ago, late Devensian marine and estuarine sediments have been deposited on the underlying glacial till sheet at altitudes ranging from more than 120 m below O.D. to at least 46 m above O.D. Similarly, raised and buried beaches and their deposits occur at altitudes from 40 m above O.D. down to around 10 m below O.D. in the estuary. During the Flandrian, sea-level has fluctuated, reaching its maximum (about 11 to 15 m above O.D.) about 6500 years ago. The typical deposit of this period is the carse clay which forms a series of extensive, fertile raised mudflats around the estuary. The calcareous marine faunas of the carse clay and older deposits are outlined.

Geodiversity and the Role of the Planning System in Scotland

Abstract The Nature Conservancy Council Earth Science Conservation Strategy (1990) had six main areas for action, including maintaining the Special Sites of Scientific Interest (SSSI) series through the Geological Conservation Review and expanding the Regionally Important Geological/Geomorphological Sites Network (now Local Geodiversity Sites; LGS). Protection of SSSIs is well understood, statutory and the planning system generally sympathetic, albeit with a few recent notable exceptions. Local Geodiversity Sites protection is achieved through local planning policy. However, the establishment of a geodiversity site system and recognition of LGS is patchy in Scotland. Many local authorities still do not have policies to conserve their local geodiversity or to give it consideration in planning. Even where LGS have been recognised, damage to sites can occur because of lack of consultation following emergency incidents. A petition in 2009 was raised unsuccessfully in the Scottish Parliament to establish a Scottish Geodiversity Duty in order that an integrated approach to geodiversity and its conservation might be achieved. The Scottish Geodiversity Forum was established in 2011 and has pursued the avenues opened by the petition and a key Scottish Natural Heritage Report. The outcome is the launch of Scotlands Geodiversity Charter and active participation in the revision of the Scottish Biodiversity Strategy.

A geological perspective on the Stone of Destiny

Synopsis The petrography of a sample detached from the Stone of Destiny during the late nineteenth century by the Geological Survey of Great Britain, is described. The observations are compared with past geological descriptions of the Stone of Destiny and speculation regarding its origin, and are set against new petrographic descriptions of samples of Old Red Sandstone lithofacies from Geological Survey collections. The lithology of the Stone resembles that of Lower Devonian sandstones from the Perth area. In particular, the texture, mineral assemblage and colour are similar to those of sandstones from the Scone Formation in the vicinity of Quarry Mill, near Scone Palace itself. It is thus possible that this area contains the bed from which the Stone was hewn, although comparable rocks may exist within other exposures of the Old Red Sandstone lithofacies in Scotland.