Sandstone Bands Research Articles

Lithofacies characteristics and depositional environment interpretations of the Middle Jurassic Fort Member rocks, Jaisalmer Formation, Western Rajasthan, India

The present study is focused on the identification of lithofacies characteristics and depositional environments for the Middle Jurassic sediments of Fort Member, Jaisalmer Formation, Western Rajasthan (NW India). Three facies associations are documented as tidally influenced fluvial, tidal/inter-tidal flat and wave-dominated shoreface facies deposits. Facies association-1 contains matrix-supported clasts, planar and flaser cross-stratified sandstone, interbedded sandstone and horizontal laminated sandstones; indicative of tidally influenced fluvial deposits. Facies association-2 characterized by herringbone cross-stratified sandstones, horizontal laminated sandstones, planar and trough cross-stratified sandstones, the alternate band of sandstone and shale, mud-crack sandstone developed on a tidal/inter tidally influence deposits. Facies association-3 consists of wave-dominated shoreface facies association consisting of wavy and lenticular beds, interference ripples, horizontal laminated sandstone, small scale planar cross-stratified sandstone, trough, and hummocky cross-stratified sandstone as well as fossiliferous limestone. Palaeoflow patterns from unipolar to bipolar indicate a change from tidal influence fluvial to marine depositional environments. The overall lateral and vertical distribution of lithofacies shows that the depositional environment was tidal-dominated fluvial channel to the marine realm.

Geochemical constraints on the depositional environment of the 1.84 Ga Embury Lake Formation, Flin Flon Belt, Canada

AbstractThe Flin Flon Belt of Canada contains Paleoproterozoic volcanic–sedimentary sequences that are related to the Trans‐Hudson Orogeny. The sequences include island arc volcanic and volcaniclastic rocks (Amisk Group) that are unconformably overlain by subaerial sedimentary rocks (Missi Group), and younger deep facies sediments. In the Flin Flon area, several north–south trending faults divide the sequences into blocks and obscure the depositional environment of the deep facies sediments. Locally, within the Flin Flon area, the Embury Lake Formation is in fault contact with island arc volcanic–sedimentary sequences of the Amisk and Missi Groups. To identify the depositional environment of the Embury Lake Formation, we used lithologic and geochemical approaches. Here, we report carbon isotopic values in organic matter (δ13Corg) and sulfur isotopes (δ34S), as well as total organic carbon and total sulfur measurements for the black shale in the formation. Samples were taken from a drill core that contains alternating bands of sandstone and black shale. Pyrite in the black shale is divided into four textural types: euhedral, vein‐type, elliptical, and microcrystalline. Microcrystalline pyrite is typically generated by microbially mediated sulfate reduction. An extremely low S/C ratio (avg. = 0.04) is consistent with lacustrine deposition. The ranges of δ13Corg (−36 ‰ to −27 ‰) and δ34S (+3.0 ‰ to +7.7 ‰) values can be explained by bacterial photosynthesis that involved Calvin cycle and acetyl CoA pathways, and sulfate reduction in a low‐sulfate environment. Considering the depositional age reported in a previous study of < 1.84 Ga, the Embury Lake Formation was likely emplaced in a lacustrine setting during the Trans‐Hudson Orogeny.

Mini thief zones: Subcentimeter sedimentary features enhance fracture connectivity in shales

This study examines the influences on fluid flow within a shale outcrop where the networks of two distinct paleoflow episodes have been recorded by calcite-filled veins and green alteration halos. Such direct visualization of flow networks is relatively rare and provides valuable information of fluid-flow behavior between core and seismic scale. Detailed field mapping, fracture data, and sedimentary logging were used over a 270 m2 (2910 ft2) area to characterize the paleo–fluid-flow networks in the shale. Distal remnants of turbidite flow deposits are present within the shale as very thin (1–10 mm [0.04–0.4 in.]) fine-grained sandstone bands. The shale is cut by a series of conjugate faults and an associated fracture network, all at a scale smaller than seismic detection thresholds. The flow episodes used fluid-flow networks consisting of subgroups of both the fractures and the thin turbidites. The first fluid-flow episode network was mainly comprised of thin turbidites and shear fractures, whereas the network of the second fluid-flow episode was primarily small joints (opening mode fractures) connecting the turbidites. The distribution of turbidite thicknesses follows a negative exponential trend. which reflects the distribution of thicker turbidites recorded in previous studies. Fracture density varies on either side of faults and is highest in an area between closely spaced faults. Better predictions of hydraulic properties of sedimentary-structural networks for resource evaluation can be informed from such outcrop subseismic scale characterization. These relationships between the subseismic features could be applied when populating discrete fracture networks models, for example, to investigate such sedimentary-structural flow networks in exploration settings.

Research on the deformation and failure evolution of sandstone under triaxial compression based on PFC2D

Through the comparative analysis of the results of the triaxial compression experiments of sandstone and the numerical simulation results of particle flow code PFC2D under the same conditions, the typical simulation curve and the corresponding simulation process were selected to analyze the evolution characteristics of the surface deformation field, the evolution characteristics of the velocity field and displacement field of the deformation localization bands of sandstone under triaxial compression. Research results show that the changes of the velocities and displacements of deformation localization bands corresponds to the change of stress during compression; In the same deformation localization band, the dislocation velocities are always in the same direction, but in the direction vertical to the localization band, the localization band sometimes squeezes and sometimes stretches; At different positions of the same deformation localization band, the dislocation velocities and extrusion velocities are both different at the same time; In the post-peak stage of loading, along the same deformation localization band, the dislocation displacements close to both loaded ends are generally greater than the ones near to the middle position of the specimen, the stretching displacements close to both loaded ends are generally smaller than the ones near to the middle position of the specimen.

Energy release rate of propagating deformation bands and their hosted cracks

Cataclastic bands and their mechanical properties within two mineralogically different sandstones have been studied. In order to investigate the propagation energy of these bands, we have used dynamic elastic moduli calculated from laboratory measurements of ultrasonic velocities using a portable ultrasonic measuring system. As a product of cataclasis and compaction, elastic moduli (uniaxial compressive and shear moduli) of the bands are different from their corresponding host rocks leading to heterogeneity and anisotropy within sandstone reservoirs. Poisson's ratio decreases in the cataclastic bands of sandstone with high quartz content as a result of compaction, while it increases within cataclastic bands of sandstone with high clay and phyllosilicate content (more than 30%). Using the calculated propagation energy rates, we investigate which mode of deformation can be more dominant in the setting of our samples, propagation of deformation band as a result of strain hardening within the cataclastic band or crack propagation inside the deformation band due to strain softening prior to the propagation of band. We further estimate the maximum length of cracks inside a deformation band which can precede further growth of the deformation band.

The boundary between the Middle Eocene Brussel Sand and the Lede Sand Formations in the Zaventem-Nederokkerzeel area (Northeast of Brussels, Belgium)

In the Zaventem airport railway cutting, to the north-east of Brussels, the upper part of the Brussel Sand Formation consists of two major units, both attributable to calcareous nannofossil zone NP14a. The lower predominantly sandy unit ZB1 (including subunits A, B and C, belonging to NP14al) is built up of sparsely glauconitic, relatively coarse tidal current deposits with nodule levels cemented by carbonate and silica, of which one shows slumping structures and is interpreted as a seismite. The uppermost unit ZB2 (also labelled D, belonging to NP14a2), composed of alternating thin fine sandstone bands and silty marls, represents the fill of a large channel. In the Berg-Nederokkerzeel sandpit the carbonate-rich Brussel Sand Formation is finer grained and more homogeneous. Here, the basal sand (unit A) is attributable to NP14a3 and consequently, younger than the section exposed at Zaventem. It is incised at its the top by a rather narrow erosive gully, filled in with well-sorted fine sand rich in washed-in molluscs (unit B), some of which seem to point to a brackish influence. The extreme top is made up of half a meter of sand with abundant Callianassa burrows and echinid fragments (unit C). From the nannofossil data it appears that, east of Brussels, at least two generations of tidal channel systems seem to have occurred within the Brussel Sand Formation, followed by a partial emersion at the end of the filling of the uppermost channel (Nederokkerzeel B). This was succeeded by a relative sea-level rise, as shown by unit C and the remains of a completely eroded fully marine deposit, reworked in the base of the overlying Lede Sand Formation. The lowest relative sea level, with at least partial emergence of the Brussels area, occurred during middle to late Biochron NP14b. In both outcrops the Lede Sand Formation displays its characteristic pale grey relatively fine-grained homogeneous nature with a stone layer near its base. It can be concluded that, at the beginning of the "Lede transgression", an erosion of older deposits, containing already lifhified stone layers, occurred. This was, apparently, at least locally, caused by storms, which could redistribute, imbricate and turn over the stones, explaining their bio-perforation on both sides. Afterwards the stones have been above water for a relatively long time, enough to allow the dissolution of the perforating organisms and consequently an important oxidation of their surfaces. These stones have subsequently been colonised by a new marine fauna. Part of the shark teeth and calcareous nannofossil assemblages found in the coarse base of the Lede Sand is definitely older than the taxa normally found in the Lede Sand Formation. These fossils are the remains of a sediment package, believed to represent the formerly "Laekenian" stage.

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.

Multispectral survey of an area of scattered drift deposits between Warwick and Redditch†

Abstract Multispectral scanning was evaluated as an aid to the rapid assessment of sand and gravel resources in areas of scattered drift deposits. In the area chosen, where glacial sands and gravels, tills, river terrace deposits and alluvium overlie Mercia Mudstone Group mudstones with thin sandstone bands, it was found possible to delineate areas of alluvium and outcrops of sandstone, but not to distinguish sands and gravels from till clays or from mudstones. The reasons for these results are discussed.

Closing remarks

I n summarizing the afternoon’s proceedings Dr Kent commented that the greater part of the new information produced had related to the Keuper, on which it now appeared that an agreed country-wide correlation would fairly easily be achieved. The amount of new information produced on correlation of sandstone bands and their dating by various of the new methods should make this objective achievable with little further work, and the relationship of the Waterstones to the Continental standard sections was well on the way to satisfactory definition. For the Bunter the only major contribution had been that of Professor L. J. Wills, whose proposal to correlate by means of cyclothems, although subject to further discussion, did appear to offer the possibility of progress on a country-wide scale. It may be hoped that the dating of major units of this kind would be eventually checked by palynological results—especially if the palynological determinations came down to species level. The base of the Trias remained a matter of considerable difficulty. He (the speaker) had always felt that the base of the Bunter Pebble Beds was most unreliable as a datum, and in practice was quite difficult to identify in open sections because of interdigitation of facies over tens of feet. The paper presented to The Royal Society, by M. E. Geiger & C. A. Hopping of Shell supplemented by additional unpublished work carried out by L. G. Horobin of B.P., suggested however a fair probability that the basal Bunter Brockelschiefer of Germany should be

Palæomagnetic Results from Northern Canada suggesting a Tropical Proterozoic Climate

THE Coppermine and September Mountains, in the north-central District of Mackenzie, North-west Territories of Canada, are composed of a thick succession of tholeiite basalt flows. Directions of natural remanent magnetization were measured on 51 oriented samples from 24 sites (Fig. 1). The sites represent 24 of the more than 60 separate flows occurring in a vertical thickness of more than 5,000 ft. The flows dip from 0° to 5° north in the area sampled. Two potassium/argon whole rock age determinations on flow rocks, made in the Isotope and Nuclear Geology Section of the Geological Survey of Canada (Wanless, private communication), gave an average age of 1,150 m.y. with a probable error of ± 100 (calculated as two standard deviations from the mean). This places the age of extrusion of the flows in upper middle Proterozoic time. The lavas conformably overlie dolomite of the Hornby Bay Group, and in places thin sandstone bands are intercalated between the flows. A sample from a red sandstone intercalation gives a direction of D = 236, I = +24, which is similar to that of the flows.

Wealden petrology : The Top Ashdown Pebble Bed and the Top Ashdown Sandstone

Wealden petrology : The Top Ashdown Pebble Bed and the Top Ashdown Sandstone

Petrology of a Wealden Sandstone at Clock House, Capel, Surrey

The topmost band of sandstone in the Weald Clay at Capel (6) is now exposed for 100 yards, and varies in thickness from 8 inches at the southern end of the face to 1 foot at the northern end. The stone is glauconitic and highly micaceous, and carries so much fresh biotite on certain bedding-planes that they are heavily darkened. Flakes of biotite and muscovite commonly reach 2 mm. in diameter, and occasionally 3 mm. No petrological facies like it is known in the older Hastings Beds outcropping to the south and south-east. The petrography of the sandstone therefore merits description, and some discussion of the problems which it raises.

ANALYSES OF SANDSTONES FROM THE MILLSTONE GRITS AT YEADON, YORKSHIRE

The sandstones referred to in this paper were obtained from a boring sunk during 1935 for the Yeadon Waterworks Company at Yeadon, 8 miles north-west of Leeds. The log of the boring has been published by Mr. Edwards, M.A. who has discussed the main points of stratigraphical and palaeontological interest.1 The present paper describes certain petrological aspects of the main sandstone bands. The specimens were kindly supplied by Mr. Edwards. I. Sandstones Investigated. The boring passed through 649 ft. of the Millstone Grits, including the main part of the Middle Grits and the top 100 ft. of the Kinderscout Grit. The recognition of standard marine bands permitted direct comparison with other areas and the following sandstone beds were identified—Guiseley Grit, East Carlton Grit, and Kinderscout Grit. Thirteen specimens were supplied as follows :— | Middle Grits{ | Guiseley Grit | .. | Specimens 1—6. | || | East Carlton Grit | .. | Specimens 7 and 8. | | Kinderscout Grit | .. | .. | Specimens 9—13. | The actual depth of each specimen in the boring is stated in Fig. 1. II. Mechanical Composition. The work done on the sedimentary petrography of the Carboniferous rocks of the Pennine area has made it clear that in such studies mechanical composition and mineral composition are to a certain degree related, and any expression of mineral composition without an accompanying statement of mechanical composition loses much of its value. Certainly this is the case if one is attempting that detailed quantitative study upon which future heavy mineral work must be based. For this ...

Volcanic vents on the coast, from Tantallon Castle eastwards to Peffer Sands and at Whitberry Point

The whole extent of the shore from Ox Road Bay to Whitberry Point was surveyed and described in the Memoir of the Geological Survey of East Lothian, 1866, by Sir Archibald Geikie, and later in 1910 by Mr George Barrow. Both these memoirs have been carefully studied. They regard the sections observed from rather different points of view. They also serve to indicate localities of special interest. The conclusions arrived at during a recent survey of this region (1925-27) differ materially from those of the two memoirs noticed above, especially in two particulars: (1) in asserting the presence of several volcanic vents, not hitherto recorded, and (2) in offering a simpler explanation of the stratigraphy of the whole region. It is proposed to deal with the geology of the coast in sections. I. Ox Road Bay to the Gegan. In Ox Road Bay the shore east of the Tantallon Vent is occupied by a smooth green volcanic ash dipping as indicated on the map (Fig. 1). On the north-east side of this ash a considerable space is covered with large blocks of sandstone, many of which appear to be in situ. Their relationship to the ash cannot be clearly seen owing to the great confusion; but they probably represent a thick band of sandstone coming up from below the ash, and may be correlated with the Gin Head Sandstone farther west. At 330 feet east of the Tantallon Vent, on high-water mark, a considerable fault is met with, cutting through

IV.—Datum-lines in the English Keuper

In the almost complete absence of fossils in the British Keuper there has been a lack of datum-lines in that formation by which we may compare the horizons of different sections. Yet in such a thick and widely spread deposit it is very desirable to have subdivisions enabling us to give the particular part of the Keuper to which a section belongs. In deposits such as the New Red formations too great stress has been laid on lithology, inevitable perhaps in the scarcity of fossils, but a source of grave errors in correlation. For example, Mr. L. J. Wills thinks that fossils found in the Keuper of Warwick have affinity, not with the Keuper, but with the Muschelkalk of Germany. Again, there are strata in the Permo-Bunter of Nottinghamshire which might be mistaken for Keuper Waterstones, if only lithology was considered. Over small areas a band of sandstone with some peculiarities may be used as a datum-line, as in the Arden district of Warwickshire and in Nottinghamshire, but these are of local value only.

XXVII. The Geology of the Isle of Man

The geological formations represented in the Isle of Man are not numerous, but some of them embrace features of special interest. If we except the extensive plain between Ramsay and the Point of Ayre, which is covered with glacial deposits, and the small areas of Old Red Sandstone and Carboniferous rocks in the neighbourhood of Peel and Castletown, nearly the whole of the remainder of the island is occupied with Lower Silurian strata. Consisting for the most part of black and grey slates, grey flags, and occasional bands of sandstone and conglomeratic grit, they bear a close resemblance to the Skiddaw slate series of Cumberland. This correlation is strengthened by the occurrence in the Manx slates of Palaeochorda major —a fossil which is characteristic of the Skiddaw series. This is the only trace of organic remains which has been hitherto met with in the Silurian rocks of the Isle. So far as the available evidence goes, therefore, the remarkable development of clay-slates in Mona may be regarded as of Llandeilo age. Their prevalent strike is north-east and south-west, which coincides with the trend of the chain of heights forming the backbone of the island. Indeed, there can be little doubt that the existence of this ridge, whose summits vary in height from 1,500 feet to 2,000 feet, must be ascribed to this cause. Few satisfactory sections are to be found inland, but along the coast-line, both on the east and west sides of the island, they are well displayed. The attempts This 250-word extract was created in the absence of an abstract

Silurian Fossils in the North-west Highlands

ON my return to-day from a geological tour in the North-west Highlands, I read with much interest the letters of Mr. Hudleston and Prof. Bonney on the above subject. The question as to the geological position of the limestone series in West Rossshire, correlated by Murchison with the Durness limestone, is one to which I devoted special attention during my late visit to the neighbourhoods of Lochs Carron, Doule, Kishorn, and Maree. The general appearance of the limestone in these areas is sufficiently like that of Durness to lead to the supposition that it is of the same age, but this of course can only be proved by fossil evidence. The conclusion at which I have arrived, however, in regard to the geological position of the limestone, and as to its relation to the so-called Upper Gneiss rocks of the central parts of Ross-shire, is in direct opposition to the views of Murchison, and accords in the main with that of Prof. Nicol. The great triangular patch at the head of Loch Kishorn consists of a series of thick beds of grey limestone, with a few bands of sandstone in an unaltered condition, and is undoubtedly dropped by faults amongst much older strata, as maintained by Prof. Nicol. Between Lochs Carron and Doule the same series is seen to rest unconformably upon much higher beds than those which it is supposed by Murchison and others to underlie at Loch Kishorn. As I purpose shortly to give a full account of these researches, I will not venture now to trespass further on your space.

Note of borings for the foundation of the Episcopal Cathedral at the west end of Melville Street, Edinburgh

The following seven borings were made in the spring of 1873, by directions of Sir Gilbert Scott, the architect of the proposed Episcopal Cathedral Church of St Mary:—No. 1. Soil, 1 foot; sandy clay (wet), 6 feet; sandstone, bands, and shale, 1 foot 5 inches; sandstone, hard, 5 inches—Total, 8 feet 10 inches. No. 2. Shale (soft and hard) and soil, 11 feet 2 inches; sandstone, hard, 5 inches—Total, 11 feet 7 inches. No. 3. Soil and loose shale, 13 feet; shale, hard, 11 feet 4 inches; sandstone, hard, 5 inches—Total, 24 feet 9 inches. No. 4. Black soil, 1 foot; boulder clay, 11 feet; shale (hard), 6 feet; sandstone band, 4 inches; shale, hard, 3 feet 8 inches; sandstone, hard, 2 feet—Total, 24 feet. No. 5. Soil, 1 foot; boulder clay, 6 feet 6 inches; shale (various), 13 feet; bands and shale, 20 feet; sandstone, 5 inches; hard bands and shale, 5 feet 8 inches—Total, 46 feet 7 inches. No. 6. Soil, 1 foot; clay, 5 feet; shale (not hard), 7 feet; black bands and hard shale, 13 feet; sandstone bands and hard shale, 2 feet; sandstone, hard, 1 foot—Total, 29 feet. No. 7. Black soil, 1 foot; clay, 8 feet; shale (pretty hard), 17 feet 8 inches; hard bands and hard shale, 3 feet 5 inches; sandstone, hard, 9 inches—Total, 30 feet 10 inches.

On the “Passage-Beds” in the neighbourhood of Woolhope, Herefordshire, and on the discovery of a New Species of Eurypterus , and some New Land-plants in them

The “Passage-beds” between the Upper Silurian rocks and the Old Red Sandstone, on the outer area of the Woolhope valley of elevation, although they have been already noticed by Sir R. Murchison, Professor Phillips, Strickland, Symonds, and myself, at Hagley, Tarrington, Ledbury, and Perton have not in this district received the full attention they deserve; for although they are of comparatively limited vertical thickness when compared with the finer and more complete sections at Downton and the Ledbury tunnel, they occupy a larger extent round the valley of Woolhope than has been previously recognized, and contain some new and interesting fossils At Putley, near the road from Ledbury to Woolhope, to the N.E. of the latter village, a remarkable bed of very hard horizontal sandstone, composed mainly of small pieces of quartz in a sandy matrix, overlying a stratum of white and yellow clay, used for making tiles, may be seen in a brickyard to the depth of about 3 or 4 feet, the blocks of sandstone averaging about 2 feet in thickness. I could find no fossils in it, and it had very much the aspect of a volcanic rock; but my friend Professor Phillips, to whom I sent a specimen, recognized it at once, and states that he believes it to have been derived from Trappean and other Plutonic rocks, though it may be presumed to be one of the bands of sandstone belonging to this series. About two miles to the south of Putley, at a farm

The Physical Structure of Merionethshire and Caernarvonshire

The view from the summit of Cader Idris is one of the most magnificent in Wales. Turning to the south, the landscape consists of a series of rolling hills, stretching as far as the eye can reach, in smoothly swelling outlines; and it is impossible not to be struck with the circumstance that, though some rise higher than others, they maintain a sort of average height, accompanied by a general gentle inclination towards the sea. Through this broad undulation innumerable valleys have been excavated. The hills have not been formed merely in consequence of disturbance of the strata; but, through the outcropping and smoothed edges of disturbed strata, many great and small valleys have been cut by old marine denudations, atmospheric disintegrations, and the action of running water. The general uniform character of the outlines of this country is due to the sameness of the rocks, which, in the main, consist of slates, occasionally varied by hard or interstratified bands of sandstone, the whole belonging to that part of the Silurian series known as the Caradoc or Bala beds, and the rocks immediately overlying.Turning northwards, a change in the character of the landscape becomes at once apparent. The mountains are broken and rugged. The summits of the Arans, the great swelling mass of Rhobell-fawr, the cliffs of Rhinog-fawr and Rhinog-fach, that guard the pass of Bwlch-drws-ar-Dudwy, the bold outlines of the Arenigs, the Moelwyns, and Cynicht, all meet the eye almost at a glance; and, far in the distance, the peak of Snowdon sharply pierces the air, rising to a height of 3,571 feet above the sea.