Marine Horizons Research Articles

Correlation of Carboniferous strata using a hierarchy of transgressive-regressive units

Carboniferous strata can be described, interpreted, and correlated using six scales of allocyclic transgressive-regressive (T-R) units. These T-R units are inferred to be the net result of deposition during cycles of sea-level change. All Pennsylvanian and Lower Permian strata constitute one second-order T-R unit, or synthem. The Pennsylvanian System contains third-, fourth-, fifth-, and sixth-order T-R units that can be correlated across both marine and nonmarine facies in the Appalachian Basin. This permits differentiation of allocyclic T-R units from autocyclic T-R units or fluvial autocyclic units. The hierarchical approach is also useful for predicting the location of marine horizons, coals, claystones, and various types of stratigraphic breaks. A hierarchical scheme of allocyclic T-R units could be combined with biostratigraphic, radiometric, and magnetostratigraphic data to form a practical chronostratigraphic framework for the Carboniferous.

Late Glacial and contemporary deposition of clay-size minerals in Makkovik Bay, Labrador

Makkovik Bay, a low-relief fjord on the coast of Labrador at 55°N, has a complex sequence of Late Glacial to contemporary sediments. X-ray diffraction analysis of the <2- μm fraction of glacial detritus, a 10,000-yrs B.P. proglacial marine horizon and contemporary estuarine sediments shows dominance of feldspar and mica, lesser amounts of quartz, chlorite and amphibole, and minor quantities of smectite and kaolinite. Significant down-fjord variations in mica were observed only in proglacial marine sequences, and are attributed to physical sorting by size in the upper water layer in a highly stratified estuary. The lack of variation of clay minerals in the contemporary muds is related to the origin of the mud from erosion, mixing and redistribution of proglacial sediments as relative sea level fell during glacio-isostatic rebound.

Diagenetic pyrite formation and sulphur isotope fractionation associated with a Westphalian marine incursion, northern England

ABSTRACTPyrite textures are described and illustrated and stable S-isotope data are presented from the Alton (Gastrioceras listen) marine horizon of the Westphalian Lower Coal Measures, from sections near Penistone in central northern England, with the object of relating the paragenetic sequence of pyrite formation to the conditions of sediment deposition and diagenesis. The earliest diagenetic pyrite is dispersed as framboidal and related textures. It is followed in the marine shale, coal and ganister by more localised but more intense pyrite deposition and replacement in a variety of textures. Most of this is precompactional in age, but some, together with pyrite in veinlets and cleat, is postcompactional. Marcasite is rare and mainly late. δ34S ratios range between −35·31‰ and +20·39‰. There is a definite trend from lighter values (−1·15 ± 6·47‰) in the marine part of the sequence to much heavier values (+12·73 ± 7·66‰) in the sediment below the coal. This allows the relationship of the earliest pyrite deposition in the coal-peat and ganister to the chemistry of their own depositional fresh water to be seen but then relates the main pyrite deposition to the influx of the marine-water sulphate of the Alton horizon, and shows the penetration of this influence downward into the coal-peat and its seat-bed.

Depositional environments of the early cretaceous Kurnub (Hathira) sandstones, North Jordan

The Kurnub (Hathira) sandstones in north Jordan, which are most probably of Early Cretaceous age, are about 300 m thick varicoloured, friable quartz-arenitic sandstones. Based on grain-size analysis, sedimentary structures, palaeocurrent, fossil content and petrography, these sandstones are postulated to be dominantly of fluvial origin with a few interfingering shallow marine horizons. A southward displacement of Jordan by at least 100 km would bring these sandstones opposite to similar rocks west of the Jordan-Araba rift, with Jordan being higher during the EArly Cretaceous.

A marine fauna from the Dartmouth Beds (Lower Devonian) of Cornwall

SummaryA brachiopod fauna is described from a marine horizon within the Dartmouth Beds at Bull Cove, Cornwall. The fauna indicates a Middle or Late Siegenian age and aspects of the palaeoecology are discussed. The Lower Devonian succession of south Devon and north Cornwall is discussed and the terms Meadfoot facies and Standon facies are proposed to replace the Meadfoot Beds and Staddon Grits of the old terminology.

Biostratigraphic ages of tertiary basalts on the East Greenland continental margin and their relationship to plate separation in the Northeast Atlantic

Palynological evidence indicates that the 4−5 × 10 5 km 3 pile of tholeiitic basalts on the central east Greenland coast was erupted in latest Palaeocene (late Landenian) and earliest Eocene (early Ypresian) time. Assignment of a precise numerical age of this interval is not yet possible, but it is evident that the eruptive episode was completed within about 3 m.y. The effusion rate was at least an order of magnitude faster than the current Icelandic rate. Marine horizons at the base and top of the pile show that its build-up was accompanied by concomitant crustal depression. It is argued that this major volcanic episode marks the initiation of plate separation between Greenland and northwest Europe. Implications with regard to spreading chronology and the magnetic polarity time scale are discussed.

Diversity and Community Structure of the Brush Creek Marine Interval (Conemaugh Group, Upper Pennsylvanian), in the Appalachian Basin of Western Pennsylvania

Nine Brush Creek localities in western Pennsylvania were trench sampled for the purpose of recovering the total fauna from each visible marine horizon. The 9 localities provided 61 samples that were disaggregated by the Amine 220 technique, washed, dried, and sieved into 305 individual samples. The recovered fossils are judged to have lived, died, and been preserved at each collecting site and are therefore members of fossil communities. This judgement is based on qualitative judgements of state of articulation, abrasion level, quality of preservation, and taxonomic associations. Animals from the sieve-sample splits were viewed microscopically to determine taxonomic composition and frequencies. Raw faunal assemblage data were adjusted to reduce the frequencies to whole numbers of individuals and, secondly, to a single generation. The purpose of making a generation correction is to reflect standing crop, which in turn provides a reasonable approximation of the once-living communities. The adjusted outcrop data were examined for faunal similarities among localities for the purpose of zoning the localities into workable groups. Two distinct faunal groups are recognized on the basis of relative water depths and distances from shore. Four shallow water and five deep water localities are inferred. The deep-water localities are characterized by low diversity molluscan faunas, whereas the shallow-water localities are characterized by high-diversity molluscan faunas. The adjusted data were further subjected to programmed diversity and equitability tests to decipher faunal succession and community structure. The diversity and equitability data were graphed for each locality and the resultant curves compared with ecological criteria such as animal habitat preferences and feeding types. These combined types of data aided in deciphering the sea-level history of the marine event at each locality. Transgressive, stillstand, and regressive phases are deciphered, along with their corresponding opportunistic, stable-mature, and relict-mature faunas. These data also show that the faunal distribution above and below the stillstand is asymmetrical.

The limits of stratigraphic distribution of Glossopteris in India

The literature reveals that controversy still persists over the lower and upper stratigraphic limits of the distribution of Glossopteris in Indian strata. A fresh approach is therefore made in this paper to evaluate these two limits from a critical reassessment of all published data, supplemented to some extent by field and laboratory investigations made by the author and some unpublished information obtained through personal communication. The lower limit is found to be considerably younger than the end of Talchir glaciation, which is not a sharp stratigraphic datum but seems to be a time-transgressive boundary represented by a succession of more than one boulder bed. The glacial phase was terminated in India, from the evidence of associated marine horizons, in the Early Permian (Sakmarian), although its onset might date back into the Carboniferous. This suggests the lower limit of Glossopteris in India somewhere high in the Sakmarian or at the base of the Artinskian. The upper limit is assessed from a reconsideration of the stratigraphic relations of the macroflora, microflora and vertebrate fauna accompanying the Permo-Triassic transition, particularly the Raniganj-Panchet sequence of Peninsular India. Results of recent research indicate the upper limit of the range of Glossopteris lies some way above the base of the Panchet Formation, i.e. at the summit of its lowermost section. This limit seems to coincide with the lower boundary of the Triassic. From the limits and pattern of the vertical distribution of Glossopteris, a simple scheme of floral zonation for the Indian lower Gondwana sequence is suggested. It is emphasized that the line of division between the lower and upper Gondwanas, which is conventionally placed at the upper boundary of the Panchet Formation from palaeontological and lithological criteria, should be defined on a biostratigraphic (particularly floral) basis, and accordingly lowered to the top of the Glossopteris-Dicroidium (transitional) zone. This zone is believed to be restricted to the lowermost beds of the Panchet Formation with very rare exceptions.

THE ARCHAEOLOGY OF A GEOGRAPHIC LABOURER: ANDREW BAY

The eminence known as Burnswark Hill towers above lower Annandale in eastern Dumfriesshire (NY 185785). Notable for its archaeological remains, it is surmounted by the defences of the largest pre-Roman hillfort in south-west Scotland and is flanked on north and south by two Roman camps, generally though perhaps erroneously referred to as siege-works. [1] From its western summit the views are extensive. To the south-west they embrace the whole of the Solway estuary and, on seemingly infrequent halcyon days, a wisp of cloud on the distant marine horizon betrays the position of Snae Fell in the Isle of Man. To the south the Cumbrian massif and the northern Pennines loom large, whilst to the east the Tyne-Solway Gap lies in full view as far as the wave-like crests of the Whin Sill, which carry the central sector of Hadrian's Wall. In the north the Southern Uplands unfold with increasing altitude to the high watershed which divides the main river-systems of southern Scotland. The archaeological remains, if not the value of Burnswark as a vantage point for the early field-surveyor, at least captured the interest of William Roy, [2] father of the Ordnance Survey.

THE ARCHAEOLOGY OF A GEOGRAPHIC LABOURER: ANDREW BAY

The eminence known as Burnswark Hill towers above lower Annandale in eastern Dumfriesshire (NY 185785). Notable for its archaeological remains, it is surmounted by the defences of the largest pre-Roman hillfort in south-west Scotland and is flanked on north and south by two Roman camps, generally though perhaps erroneously referred to as siege-works. [1] From its western summit the views are extensive. To the south-west they embrace the whole of the Solway estuary and, on seemingly infrequent halcyon days, a wisp of cloud on the distant marine horizon betrays the position of Snae Fell in the Isle of Man. To the south the Cumbrian massif and the northern Pennines loom large, whilst to the east the Tyne-Solway Gap lies in full view as far as the wave-like crests of the Whin Sill, which carry the central sector of Hadrian's Wall. In the north the Southern Uplands unfold with increasing altitude to the high watershed which divides the main river-systems of southern Scotland. The archaeological remains, if not the value of Burnswark as a vantage point for the early field-surveyor, at least captured the interest of William Roy, [2] father of the Ordnance Survey.

THE GEOLOGY OF THE URE VALLEY WATER MAIN TRENCHES 1969–71

Summary Rocks of Namurian age, exposed in 11 miles (18km) of pipeline trenches, are described, and details of new localities for several marine horizons are given. The Marsdenian Stage has been proved, for the first time in the area, at an exposure near Winksley.

The structure of the Taff Gorge area, Glamorgan, and the stratigraphy of the Old Red Sandstone—Carboniferous Limestone transition

AbstractLithostratigraphical and structural mapping of the Taff Gorge area, Glamorgan, has revealed a number of E‐W trending folds and thrusts. These were developed during the early stages of the Hercynian deformation as a result of an approximately N‐S principal compressive strain. Coeval with the folding, a conjugate set of sub‐vertical wrench faults, symmetrical about the principal compressive strain, divided the area into tectonic blocks and to some extent controlled the progressive development of folds and thrusts within the individual blocks. Later Hercynian deformation gave rise firstly to oblique‐slip and finally to dip‐slip movement on the faults.The lithological transition between the Old Red Sandstone and Carboniferous Limestone is described in detail, including the diagenetic history of the limestones. Marine horizons are shown to be present within the dominantly fluviatile Old Red Sandstone, and the base of the Carboniferous Limestone is defined at the base of the lowest limestone of the continuous marine sequence. Studies of spores, macroplants, conodonts and brachiopods indicate that the whole of the Upper Old Red Sandstone and Lower Limestone Shale in the Taff Gorge are of Tournaisian age.

Carbon and oxygen isotope ratios in diagenetic carbonates from marine sediments

The isotopic composition of some sixty samples of penecontemporaneous diagenetic carbonates from marine horizons shows that they are strikingly different from normal marine limestones. The variation of C 13 ratio is 5·6 per cent, the lightest carbonate measuring -54%. A mechanism for the formation of such light carbon dioxide is postulated, involving the enzymic decarboxylation of organic compounds at low temperatures. A study of the oxygen isotopic composition of coexisting calcite and rhodochrosite indicates that, whereas the latter has retained its isotopic composition from the time of precipitation, the calcite has undergone equilibration during diagenesis. Isotopic measurements on such diagenetic carbonates would confuse palaeoenvironmental studies but may throw light on the processes of diagenesis.

Notes on the Millstone Grit of the North Crop of the Pembrokeshire Coalfield

The two cliff sections, one at Marros and the other between Settling Nose and Druidston Haven, at the eastern and western ends of the north crop of the Pembrokeshire Coalfield, are described in detail. Several undescribed marine horizons, including goniatite bands, are reported. The strata are correlated with the Millstone Grit of the north crop of the South Wales Coalfield, and the sub-Namurian unconformity is discussed.

FAUNAL MARKER HORIZONS IN THE MIDDLE COAL MEASURES OF THE NORTH WALES COALFIELD

Summary Marine and non-marine fossils have been found recently above certain coal seams of the Middle Coal Measures in opencast workings, and underground at neighbouring pits, in North Wales. Previous work on this subject has been confirmed in part, and enlarged upon by the discovery of three marine horizons new to the coalfield. The widespread marine band occurring about the middle of the Anthraconaia modiolaris Zone has been proved in situ for the first time, and its position in relation to well-known coals firmly established. Names are proposed for the marine bands, and correlation with other coalfields is made in well-authenticated instances and suggested in others. The marine and non-marine faunas are listed in the text.

Extension verticale des alethopteridees et formes voisines dans le bassin du Nord et du Pas-de-Calais

Abstract On the basis of examination of several hundred newly collected specimens of Carboniferous Alethopteridea and revision of previously collected material from the Nord-Pas-de-Calais coal basin, France, the vertical ranges of different species (Alethopteris, Lonchopteris, and Pecopteridium) are established precisely. The vertical distribution of these forms indicates that the coal measures of northern France can be divided into two major zones, with their boundary a little above the Rimbert marine horizon.

Lithology and zoology of an Antarctic Ocean bottom core

Polar deep-sea cores provide material for a thermo-time scale. An Antarctic Ocean deep-sea core from the Ross Sea can be correlated with three others from the same area, dated by Urry and described by Hough (1950). All the cores showed several alternations of glacial marine sediment and of fine-grained sediment which is apparently non-glacial. Organic deposits, notably radiolarian tests, are associated with glacial marine horizons and are lacking in the non-glacial ones, thus providing a zoological criterion for correlation. This association of sediments suggests inhibition of solar energy during deposition of strata where organic remains are lacking. For the period of sedimentation represented by the core, a record of Pleistocene and recent thermal regimen is provided. Amelioration of climates over the past 6000 years is indicated in this record.

New Marine Horizon in the Conemaugh Formation

New Marine Horizon in the Conemaugh Formation

The Pleistocene Epoch in East Anglia

Abstract The sequence of Pleistocene deposits in East Anglia is tabulated. The following aspects of the Pleistocene are discussed and summarized: boundaries of the Pleistocene, glacial and preglacial, ice advances, interglacials, glaciations, marine horizons, climate and periglacial features. Correlations are given between the Pleistocene deposits of East Anglia and the continent.

The Pleistocene Epoch in East Anglia

AbstractThe sequence of Pleistocene deposits in East Anglia is tabulated. The following aspects of the Pleistocene are discussed and summarized: boundaries of the Pleistocene, glacial and preglacial, ice advances, interglacials, glaciations, marine horizons, climate and periglacial features. Correlations are given between the Pleistocene deposits of East Anglia and the continent.