Kincardine Basin Research Articles

High-frequency sequence stratigraphy using syntactic methods and clustering applied to the upper limestone coal group (Pendleian, E1) of the Kincardine Basin, United Kingdom

We define a distance between sedimentary successions to compare their dissimilarity formally. Distance definition is based on attributed syntactic representation. One-dimensional successions can be represented by a string of lithofacies symbols sequentially or vertically. Each symbol can also have a vector of attributes that can provide other information on lithofacies such as thickness. The distance of any two successions is then defined consisting of its syntactic and attribute subdistances. Syntactic distance measures difference of vertical lithofacies change between two successions and attribute distance measures difference of thickness of corresponding lithofacies. Clustering is used to test validity of distance definition and its potential application to analysis of cycle-dominated sedimentary successions. Example is from the Namurian-A succession in Kincardine basin, central Scotland. There are 56 cycles in intervals of about 300 m each in two boreholes. Recognition of intermediate cycles depends on correctly determining of types of these short cycles and their vertical stacking pattern. Intermediate cycles have better potential in high-resolution stratal correlation regionally. Syntactic clustering results show that 56 short cycles can be classified into four groups with distinctive geological interpretation, which further helps reveal hierarchical cyclic architecture of the whole succession.

The Ochil Fault and the Kincardine basin: key structures in the tectonic evolution of the Midland Valley of Scotland

The Ochil Fault, one of the most prominent tectonic features in the Midland Valley of Scotland, juxtaposes Lower Devonian volcanic rocks against late Westphalian strata, implying a possible vertical displacement of up to 4 km. The Kincardine Basin in its hanging-wall, although actively subsiding during the greater part of the Silesian, trends generally N–S, perpendicular to the Ochil Fault, and its Silesian sedimentary record shows little sign of tectonic control by that fault. It is proposed that the Ochil Fault was initiated, possibly as a sinistral strike-slip feature, in the Devonian, but acted as a sidewall fault during the early evolution of the Kincardine Basin, attributed to extension on a hypothetical pre-Brigantian fault along the Bo'ness Line on the east side of the basin until late Namurian times, when active extension ceased. Both faults were probably buried during late Namurian and Westphalian times. Reactivation of the Ochil Fault during end-Carboniferous N–S extension, dated by quartz-dolerite emplacement, was responsible for probably at least 2 km displacement. including the presently visible footwall uplift. It is suggested that the hanging wall may have contained a Permian basin, now removed.

Syntactic Simulation of 1-D Sedimentary Sequences in a Coal-Bearing Succession Using a Stochastic Context-free Grammar

ABSTRACT Syntactic pattern recognition (SPR) provides a new symbolic computing paradigm that has a great potential for application in sedimentologic and stratigraphic theory. In an SPR system, a formal language consists of a set of sentences; each sentence is a string of terminal symbols (or words); a grammar is used to characterize syntactic structures of the language, which tells whether or not a specific sentence belongs to the language. A language represents a class of patterns that are similar to each other in some sense. A sentence from the language then represents an individual pattern of the class. The grammar defines the legality of members of the class in general. There are several key subdomains in this methodology, such as grammar inference, language generation or sim lation, and language parsing. The objective of this paper is to show the possibility of using geological knowledge, obtained by domain experts (here sedimentologists), to construct valid grammars characterizing the vertical structure of different orders of sedimentary sequences, by applying the methodology to the analysis of a coal-bearing succession of the upper Limestone Coal Group, Pendleian (E1) in the Kincardine basin, Central Scotland. First, complete successions from two boreholes are encoded into syntactic strings of lithofacies symbols. Five groups of different high-frequency sedimentary sequences have been recognized. These high-frequency sequences combine to form a lower-frequency sequence. This geological knowledge is used in a heuristic sense to manually construct grammars f r each of the five groups of sequences and for the whole succession. Finally, the constructed grammars, together with a thickness simulation for each lithofacies, are used to generate similar sedimentary sequences to test the validity of the grammars and therefore their further application to a formal analysis of sedimentary sequences. Comparison of simulated sequences with real sequences indicates that SPR is an encouraging technique in the analysis of sedimentary sequences.

Orbital-climatic forcing of Namurian cyclic sedimentation from spectral analysis of the Limestone Coal Formation, Central Scotland

Abstract The Limestone Coal Formation of the Glasgow-Stirling area of the Midland Valley of Scotland was deposited in a composite basin divisible into the fluvially-influenced or proximal Kincardine Basin in the east and the distal, delta-dominated Kilsyth Trough. Three main factors influenced deposition and determined the geometry of the various lithologies: tectonism, glacioeustatic changes and localized irregular crevassing/avulsion processes. If the sea-level changes were induced by orbital-climatic control of global ice volumes, then the resulting sedimentary cyclicity might be expected to be regular (near-constant wavelength). However, the irregular processes would produce superimposed irregular sedimentary cyclicity. In this study spectral analysis of time series was used to test for regularity and to distinguish the various forms of sedimentological control acting within the basin. Six localities spanning proximal to distal settings, and exactly the same stratigraphic intervals in the upper part of the formation, were used. Digitization of rock types using different numeric codes for coal, claystone, siltstone, fine-, medium- and coarse-grained sandstone was used for time series generation. Blackman-Tukey Fourier power spectra revealed that in the lower half of the sections four localities contained evidence for regular cyclicity significant at the 90 0.000000e+00vel. In the upper half of the data only one section revealed regular cyclicity. However, following decompaction the same regular cyclicity was detected in the lower part of the data, but with a considerable concentration of variance at particular frequencies, the significance had risen to 95%. In the upper data decompaction revealed two regular cycles. The decompaction procedure appears to have substantially removed compactional distortions related to rock type. Very crude estimates of the periodicity of the regular cycles indicate that a high-frequency, possibly obliquity or short eccentricity cycle is involved. All the regular cycles detected in the decompacted series occur in dominantly distal fluvio-deltaic sections. This suggests that the main signal relates to successive progradation of deltas in distal settings under regular glacio-eustatic control. Recategorizing the data into simple non-sandstone/sandstone and coal/non-coal categories revealed no major changes in the spectral results. This supports the model of the cyclicity as arising from a simple grain-size oscillation related to deltaic progradation. The lack of regular cyclicity in the more proximal areas and in the upper half of the data probably reflects fluvial sedimentation producing more irregular grain-size variations related to channel avulsion, crevassing and meander migration plus, perhaps, increased hiatuses and the influx of coarse siliciclastic material forming thick wedges of multi-storey sandstones. The study illustrates the importance of applying decompaction and of using multiple sections for the study of regular cyclicity in cyclothem series.

Evidence of tidal influences in Arnsbergian rhythmites in the Kincardine Basin

Synopsis Distinctive, vertically accreted rhythmitcs, in which evenly stratified bands of fine-grained silty sandstone alternate with much thinner bands of silty mudstone, overlie the thick marine mudstones above the Orchard and Calmy limestones in the Upper Limestone Group of the Kincardine Basin, east of Stirling. Each sandy band, together with the overlying mudstone band, is thought to represent a tidal bundle, with the sandstones being deposited during the more rapid stages of tidal flow and the mudstones during slack water. Successive sandstone bands are alternately thick and thin, reflecting dominant and subordinate tides, so that the mudstone bands are grouped into pairs. The rhythmites are similar to some Holocene vertically accreted tidal deposits, but more closely resemble Pennsylvanian tidal rhythmites in the Illinois Basin in which regular neap—spring—neap tidal cycles have been identified. Marine flooding was unusually widespread and deep during the major transgressions associated with the two limestones. This flooding may have produced wide, funnel-shaped inlets which amplified the tidal range, as well as ponding back rivers and consequently markedly reducing siliciclastic input into the basin. Tidal processes probably influenced British Carboniferous sedimentation more commonly than has hitherto been supposed.

Sedimentological evidence for a major subsurface fracture system linking the eastern Campsie and the eastern Ochil faults

Synopsis Evidence for intra-Carboniferous and end-Carboniferous right-lateral strike slip within the Midland Valley is concentrated along lineaments which reflect major subsurface fracture systems. One such lineament runs ENE below the Kincardine Basin and joins the eastern Campsie Fault to the eastern Ochil Fault. This moved right-laterally during the deposition of the Passage Group, as proved by contemporaneous movements of its associated oblique folds. The hinge line between the Tulliallan Trough ‘low’ and the Bogside Saddle ‘high’ follows this lineament. The ‘low’ controlled the locus of the major Saline Channel Belt throughout most of the Namurian, whereas unusually thick peats commonly accumulated over the ‘high’. Reversals of apparent downthrow along this hinge reflected movements, probably right-lateral strike slip, along the underlying lineament. Low-angle detachments may explain the absence of any major ENE–WSW trending surface fracture above the lineament in the Kincardine Basin. The lineament, which probably extends WSW below the eastern part of the Milngavie–Kilsyth Fault to underlie the Paisley Ruck, may have been initiated as a Riedel Shear by right-lateral strike-slip along the Highland Boundary Fault, or it may reflect a reactivated Late–Caledonian left-lateral strike-slip fault system.

Allocycles and Autocycles in the Upper Part of the Limestone Coal Group (Pendleian E1) in the Glasgow–Stirling Region of the Midland Valley of Scotland

AbstractThe upper part of the Limestone Coal Group (Pendleian E1), between the major marine transgressions of the Black Metals and the Index Limestone, represents an early example of ‘coal measures’ facies. It comprises a distal and a proximal facies association. The distal facies association, which was subject to relatively strong marine influences and included both deltaic and fluvial elements, is characterized by a regular ‘layer‐cake’ succession with laterally‐persistent lithological members. By contrast, the proximal association, which was more subject to fluvial influences and is typified by the variable Bannockburn Main Complex, is characterized by abrupt lateral changes in lithofacies.The distal facies association is dominant in the west of the Kilsyth Trough, but proximal facies intercalations increase eastwards, so that they constitute a fairly high proportion of the succession in the Kincardine Basin, particularly in areas of locally‐increased tectonic subsidence that were frequently occupied by major channel belts.Some of the sheet sandstones within the distal association have a lower, upward‐coarsening portion succeeded by a coarser‐grained, erosive‐based, upward‐fining portion. The resulting ‘two‐storey’ profile may reflect deltaic sand bodies having been suceeded by fluvial sand bodies, following a general fall in base level.Linear regression lines showing the relationship between the number of horizons colonized by vegetation and net subsidence, suggest that local autocyclic, tectonosedimentary processes, such as delta switching, channel migration, and avulsion, were superimposed upon a widespread allocyclic, probably glacial‐eustatic, process. The former processes were most effective within the proximal facies association and in the Kincardine Basin and the latter in the distal association and the Kilsyth Trough.

The influence of basin subsidence and depositional environment on regional patterns of coal thickness within the Namurian fluvio-deltaic sedimentary fill of the Kincardine Basin, Scotland

Summary Quantitative studies of a varied spectrum of Namurian fluvio-deltaic sediments deposited in Scotland’s most rapidly subsiding Namurian basin, the Kincardine Basin, have revealed the following three simple regional geometrical patterns of coal thickness: (i) basin patterns, (ii) inverse basin patterns and (iii) wedge patterns. These characterize both the overall thickness of coal within a given stratigraphical interval and the thickness of some individual coal seams. The patterns become clearer once local sedimentary and tectonic effects have been filtered out by trend-surface analysis. In a basin pattern coal thickness is closely related to the net subsidence of the basin. In contrast, in an inverse basin pattern coal-forming peat was selectively preserved on the flanks of the basin and vegetation growth was inhibited in the centre by repeated flooding and channel erosion. A wedge pattern shows coal thickness increasing fairly regularly right across the basin, so that it is directly linked to net subsidence on only one flank. Such a pattern can be linked to saline-water incursions from one direction or to optimal peat growth in a locality sheltered from repeated flooding. Similar coal-thickness patterns seem to be present in some other basins, of various ages, scattered over the world.

SOCIETY ACTIVITIES 1986

January 18th: Sheffield The geology of precious stones: New aspects of diamond geology. J. B. DAWSON Gemstones: R. A. HOWIE February 15th: Leeds Aspects of Palaeozoic volcanicity: Introduction E. H. FRANCIS The Stockdale (Yarlside) Rhyolite — a rheomorphic ignimbrite? D. MILL WARD & D. J. D. LAWRENCE Late Caledonian subvolcanic vents and associated dykes near Kircudbright, S. W. Scotland N. M. S. ROCK, C. COOPER, J. W. GASKARTH & P. J. HENNEY Geochemistry and tectonic significance of the Lower Carboniferous Cockermouth Lavas, Cumbria. R. MACDONALD & B. H. WALKER Penecontemporaneous structures of volcanic origin in an Upper Limestone Coal Group coal seam in the Kincardine Basin, West Fife, Scotland. J. A. M. BARNETT

Fracture patterns related to volcanic necks and pipes in an Upper Limestone Group (Namurian) coal seam in the Kincardine Basin, West Fife, Scotland

SUMMARY In the N.C.B’s Longannet mines, on the eastern flank of the Kincardine Basin, the Upper Hirst Coal Seam is disturbed by two sets of fractures. The earlier fractures are believed to have been induced by volcanism before the coal seam was fully compacted; they are on a small scale and are usually accompanied by minor intructions soft-sediment deformation. Some appear to be radial or concentric to a known neck at Bogside and all can be readily distinguished from the later and larger mainly E-W fractures, which resulted from end-Carboniferous tectonism The detail provided by mining offers a unique opportunity to document such disturbances induced by pipe emplacement and their recognition can be put to practical use in predicting the location of other pipes ahead of the working areas.

Facies breaks in the Scottish Passage Group and their possible correlation with the Mississippian—Pennsylvanian hiatus

Synopsis The Scottish Passage Group (Namurian E 2 to Westphalian A) contains many minor disconformities, but its thickest and most complete development in the Kincardine Basin east of Stirling reveals only three major depositional breaks or facies changes sufficiently important to be considered as possible correlatives of the Mississippian-Pennsylvanian hiatus of North America. They are here named Horizons 1 to 3. Even in the area of maximal subsidence, Horizon 1 just above the Castlecary Limestone is marked by deep channelling. Despite the following flood of coarse sandy detritus, widespread marine transgressions continued (Nos. 1 to 2 Marine Bands). Horizon 2, which lies just above No. 2 Marine Band, heralded a regressive period with meandering river environments and only one local marine incursion. Above No. 3 Marine Band Group with its renewed widespread marine transgressions, Horizon 3 marks the onset of another regressive period when marine bands became impersistent, thin and faunally impoverished, e.g. Nos. 5 and 6 Group, overbank ‘fines’ were seldom preserved and braided rivers possibly became dominant. Horizon 1 is much the best example of a major regression during the Scottish Namurian. Nevertheless biostratigraphical evidence favours Horizon 2 as being more probably equivalent to the Mississippian-Pennsylvanian hiatus.

Cycles and subsidence: their relationship in different sedimentary and tectonic environments in the Scottish Carboniferous*

ABSTRACTTen data sets have been collected from stratigraphical intervals in the Upper Carboniferous of Central Scotland. They represent six structural units and both distal and proximal deltaic environments, plus a meandering river environment. All show a definite tendency towards a linear relationship between the number of deltaic or fluvial cycles and the total thickness of strata in the interval. This relationship is, however, much stronger in sequences laid down in actively subsiding depositional basins than in areas where subsidence is thought to have been controlled by block faulting in the basement or in areas where there is no clearly defined pattern or subsidence. With respect to facies, the relationship is less close in successions that were frequently affected by widespread marine transgressions.The slopes of linear regression lines fitted to the data sets vary much more than had hitherto been supposed. Thus they are no longer thought to provide possible evidence of some ubiquitous underlying process, such as ductile flow in the upper mantle, which affected all the structural units equally. The line which represents proximal deltaic deposits of Westphalian A age in the Kincardine Basin slopes twice as steeply as any of the eight lines representing other dominantly deltaic successions and considerably more steeply than the line representing a succession of Namurian fluvial cycles.Second‐ and third‐degree polynomial regression lines were also fitted to each data set but these generally satisfy little more of the total variation than do the corresponding linear regression lines, and F‐test results indicate that the gains are not statistically significant. Eight of the second‐degree lines however share a common shape that suggests a general tendency for both deltaic and fluvial cycles to be somewhat thicker in the areas of greatest net subsidence.

Some Namurian (E 2 ) paralic sediments in Central Scotland: an investigation of depositional environment and facies changes using iterative-fit trend-surface analysis

The effectiveness of trend-surface analysis when applied to geological problems has been greatly increased by the use of iterative-fit trend surfaces, in addition to conventional overall-fit surfaces, because the former surfaces generally satisfy a considerably higher proportion of the total variation than the latter, yet remain completely objective. Such trend surfaces have been used, together with conventional stratigraphical and sedimentological methods, in an analysis of the unusually thick and laterally-persistent cycle which lies between the Upper Hirst and Plean No. 1 coals and includes the Calmy Limestone. In the differentially-subsiding Kincardine Basin thin, laterally-impersistent coals and seatearths split the upper part of the cycle into a series of thinner cycles. The regional sedimentation patterns of most of the variables studied are related to the pattern of total thickness of strata and hence to net subsidence. An exception is the Upper Hirst Coal which thickens fairly regularly eastwards. The sediments resemble those in modern deltas and reflect an initial widespread marine transgression followed by the readvance of deltas. A whole series of minor deltalobes or crevasse systems progressively filled up the basin until, in Plean No. 1 Coal times, coalswamp vegetation recolonized almost the entire area.

Trend-surface analysis of stratigraphic thickness data from some Namurian rocks east of Stirling, Scotland

Synopsis Borehole data for part of the Namurian (E 1 Zone) east of Stirling show that a single thick bed of shale, known as the Black Metals, passes shorewards into a dominantly sandy succession. Trend analysis of these data has revealed features not previously recognised in an earlier study. These features include: (1) a rather abrupt transition between a shelf-like area near Stirling and the differentially subsiding Kincardine Basin to the east, and (2) a tongue of sand that extends south-westwards from Saline and corresponds to one of the axes of maximum subsidence.

Shoreward facies changes and their relation to cyclical sedimentation in part of the Namurian east of Stirling, Scotland

Synopsis A thick, persistent bed of shale known as the Black Metals, which lies near the middle of the Limestone Coal Group (Namurian, E 1 Zone), was deposited partly under marine conditions. It may be traced with little change over the Central Coalfield, but in the Kincardine Basin east of Stirling it becomes split by sandy beds which increase progressively in number and thickness eastwards so that within only 10 to 15 miles the whole succession is dominantly sandy. Seatearths and coals also appear. Variations in thickness and lithology are traced by means of 80 sections and illustrated by a series of maps. The undivided Black Metals may be considered as part of an unusually thick and persistent cycle, formed during a general, possibly eustatic, rise of sea-level. The complex lithological variations east of Alloa and Grangemouth are thought to be due to the interplay of this major marine transgression and local processes of subsidence and sedimentation, probably including the progressive building out and abandonment of local deltas topped by vegetation, which gave rise to a series of thin, impersistent, coal-bearing cycles within the Black Metals. Faunal alternations in the all-shale successions of the west may reflect the formation of coal-bearing cycles further east.