Green Mudstone Research Articles

Major displacements in northland, New Zealand; micropaleontology and stratigraphy of Waimamaku 1 and 2 wells

Abstract Two wetls drilled for petroleum in the Waimamaku Vatley penetrated Late Cretaceous and Paleogene sedimentary rocks displaced on a scale not previouslv known in Northland. The sequences are as fallows: Waimamaku No. 1 (NI8/01) 0-1900 ft (0-580 m) highly disturbed Mid Eocene, Paleocene and Late Cretaceous mudstone and sandstone. 1900-4175 ft (580-1273 m) apparently undisturbed Late Cretaceous sandstone and mudstone. Waimamaku No. 2 (NI8/0L) 0-343 ft (0-105 m) surficial slumped materials. 343-1038 ft (105-316 m) Early Eocene to Late Paleocene calcareous mudstone. 1038-3250 ft (316-990 m) Paleocene muds tone and siltstone. 3250-3535 ft (990-1077 m) latest Cretaceous muds tone and siltstone. 3535-7950 ft (1077-2423 m) Late Cretaceous non-calcareous sandstonesandstone, siltstone and red and green mudstones. 7950-8894 ft (2423-2711 m) highly disturbed mainly Oligocene and Late Eocene calcareous mudstone and argillaceous limestone with Mid Eocene, Paleocene and Iatest Cretaceous calcareous mudstones. 889...

A reconnaissance of the sedimentology of lower Silurian mudstones, English Lake District

ABSTRACTPolished slabs and thin sections of lower Silurian graptolitic mudstones and interbedded barren mudstones show three main lithologies are present (a) unfossili‐ferous green mudstones, sometimes with indistinct silt laminae, (b) a similar black pyritic lithology, with rare graptolites, (c) striped mudstones, with prominent carbonaceous and silt laminae, and common graptolites. The abundance of silt laminae suggests that the striped mudstone facies represents the highest energy depositional conditions. Comparison of sedimentary structures with modern deep sea muds suggests this facies is distal turbidite. Graptolite preservation was favoured by rapid burial.

Interpretation of Miocene Shallow Marine Depositional Environments Using Sedimentary Structures: ABSTRACT

Comparison of sedimentary structures in certain sedimentary rocks with those that form in the modern environment can provide a powerful interpretive tool. An example can be drawn from a well-exposed middle Miocene marine-nonmarine transition in the southeastern Caliente Range, California. Within this transition, shallow-marine sandstone (part of Branch Canyon Sandstone) intertongues on the northwest with marine siltstone (Saltos Shale Member of the Monterey Formation), and intertongues on the southeast with nonmarine redbeds (part of the Caliente Formation). Flow structure in extrusive basalts in the upper part of the transition and paleocurrent features in overlying Miocene alluvial deposits indicate that the shoreline at the time of deposition trended north-northwest. > The marine-nonmarine transition consists of a succession of individual progradational sequences that extend westward (seaward) into marine strata. The sequences exhibit a fairly consistent internal stratigraphic arrangement. A typical complete sequence has a basal unit of unbedded siltstone (Saltos Shale) lying on an erosion surface. A thin zone of conglomerate commonly occurs within the siltstone directly above the lower contact. The siltstone grades up into bedded or unbedded fine-grained sandstone (Branch Canyon Sandstone). This fine sediment is sharply overlain by a coarse, pebbly, crossbedded facies of the Branch Canyon, which grades upward into finer and predominantly planar-bedded sandstone. The planar-bedded sandstone grades up into muddy structureless sandstone that in turn g ades up into red or green mudstone (Caliente Formation), which caps the sequence. The progradational nature of the sequences implies that the fine-grained sandstone near the base was deposited in the marine environment somewhat shoreward from the gradationally underlying siltstone, which locally contains marine invertebrates. Bedding, where present in the fine sandstone, is defined by concentrations of biotite; the bedding is either planar or shows medium- and small-scale cross-stratification. Bioturbational disruption abounds. Crossbedded lenses of well-sorted granular sand are interbedded with the fine sand in its upper part. Foresets in these lenses dip predominantly toward the southeast. Similar structures form in response to the passage of waves in modern high-energy environments. The foreset orientation thus suggests that during the time of deposition the wav s approached from the northwest. The coarse, pebbly sandstone that sharply overlies the fine-grained sandstone is the thickest and best exposed unit of most sequences. Bedding is generally well developed, and bioturbational structures are rare. Pebbles tend either to occur as lag deposits scattered along extensive erosion surfaces within the sandstone or to be concentrated within conglomeratic beds. Crossbedding is abundant and dips predominantly west-southwest (offshore); a small secondary mode dips south-southeast. This secondary mode may reflect the influence of longshore currents resulting from the oblique approach of the waves with respect to the shoreline. A few large-scale crossbedding units dip east and southeast and suggest the presence of offshore bars trending oblique to the coast, parallel with the prevai ing wave crests. The dominantly offshore-dipping crossbeds are best explained as the result of rip currents. The erosional contact at the base of the coarse sandstone resembles the contact formed at the base of rip channels in the modern environment. The planar-bedded sandstone in the upper part of the sequence is well sorted and contains planar concentrations of magnetite that resemble those formed on the upper foreshore of modern beaches. Many planar laminations are inversely graded like those that form at present in the upper swash zone. Where attitudes were measured, most of the planar beds dip gently seaward (west), which also supports a beach origin. End_Page 431------------------------------ The overlying structureless muddy sandstone may represent deposition in a vegetated back-beach environment. The redbeds of the Caliente Formation probably formed in coastal swamps, lagoons, or alluvial plains. End_of_Article - Last_Page 432------------

Sedimentary Environmental Control of Sandstone-Type Uranium Deposits: ABSTRACT

Uranium deposits of the Rocky Mountain area are present in fluvial sandstones that were derived from granitic highland source areas and deposited in adjacent intermontane basins. The sandstones are arkosic to arkose in composition and contain a small percentage of carbonized plant debris and pyrite, medium grained to conglomeratic in size, subrounded to angular in shape, and are poorly to moderately sorted. The sandstones intertongue and are interbedded with green mudstone. The host sandstone sequence represents a change in tectonic and/or climatic conditions. A local or regional unconformity is present at the base of the sequence and the character of the rocks is commonly substantially different. The climate was temperate and humid, and the groundwater level was very near the surface. The oxidation-reduction potential was low, which caused the carbonization of woody debris and the formation of pyrite, a condition also favorable for the precipitation of uranium and the other commonly associated metals. The depositional pattern of the aggrading streams was influenced by both tectonic and topographic elements of the area being buried. Following deposition and burial further tectonic events induced changes in the hydrodynamic system which caused an invasion of the reduced sediments by an oxidizing cell that obtained much of its energy from the oxidation of the pyrite. The oxidizing cell mobilized the uranium and other susceptible elements and swept them ahead. Where the cell encountered resistance from variations in thickness of the sandstone units its progress was impeded, therefore areas of pinchouts or intertonguing of sandstone and mudstone tend to be favorable areas for the localization of uranium mineralization. End_of_Article - Last_Page 358------------

Petrology and Mineralogy of Watt Mountain Formation, Mitsue-Nipisi Area, Alberta

ABSTRACT The Middle Devonian Watt Mountain Formation and its Gilwood Sandstone Member are described from cores of twelve wells in the Mitsue area and two in the Nipisi area. The formation consists of interbedded sandstone and mudstone, with a dolomite unit near the base. Sandstone petrography was studied in twenty-eight thin sections, and mudstone mineralogy in ten samples by X-ray diffraction and differential thermal analysis. The Gilwood Sandstone Member is a poorly to moderately well sorted, mainly feldspathic sandstone in the Mitsue area and an arkose in the Nipisi area. The primary cement is carbonate, which partly replaces the matrix, and which is in turn partly replaced by anhydrite. The brown to green mudstones of the Watt Mountain Formation consist mainly of quartz, dolomite, feldspar, illite, chlorite, and minor amounts of anhydrite. The colour is not related to iron content but probably is related to the oxidation state of the iron. The composition of the Gilwood Sandstone indicates that the source area was primarily an igneous-metamorphic terrain, most probably the Peace River high. The environment of deposition of the Watt Mountain Formation in the study-area was near-shore, deltaic or coastal plain, probably ranging from shallow-marine to continental. Differences in the composition of the Gilwood Sandstone between the Mitsue and Nipisi areas are probably due to different distances of transport and to slightly different environments of deposition.

A New Interpretation of the Llandovery Sequence of North Connemara, Eire

AbstractThe historical development of the stratigraphic nomenclature of the Llandovery of north Connemara is described. The lowest beds are red sandstones and interbedding keratophyre passing up into a complex sequence of grey, green and red clastics with shelly facies fossils. Above this are red and green mudstones and siltstones with rare graptolites. In the east these are overlain by coarse sandstones and conglomerates. The conglomerates are probably allochthonous. In the west this coarse facies is developed earlier and laterally interfingers with the shelly facies clastics and overlying mudstones. The sub-Wenlock unconformity reported by McKerrow and Campbell from this region is reinterpreted as an appearance of this interfingering.

Sedimentary History of Upper Ordovician Geosynclinal Rocks, Girvan, Scotland

ABSTRACT The Kilranny Conglomerate, Ardwell Flags, Whitehouse Formation, and Barren Flags succession was deposited near the Northwest margin of the Caledonian Geosyncline. The Kilranny Conglomerate (0-500 ft) has been interpreted in the literature as a slide conglomerate and the Ardwell Flags (1000 ft) as a deep-water turbidite formation. A reinterpretation is necessary because in the Kilranny Conglomerate the consistent imbrication of discoidal pebbles, and the clay-free nature of the sandy gravel layers, indicate deposition was in relatively shallow water by strong southwest-flowing ocean currents. Similarly the current-ripple thin sandstones, intraformational flat-pebble conglomerates, and intraformational sandstone folds in the Ardwell Flags at the Ardwell foreshore were all formed by a trong, southeast-flowing ocean current system; in situ algal mats prove that water depth was shallow. Many graded, sandy limestones in the limestone flysch sequence (165 ft) in the lower part of the Whitehouse Formation contain cross-bedded dunes previously unrecorded in graded limestones. The dunes were deposited in the lower flow regime. A dune division is added to the sequence of five internal divisions described by Bouma (1962) in the ideal graded sandstone or limestone bed. Graded sandstones in the 90-ft flysch-like sequence in the middle part of the Whitehouse formation and in the 800-ft Barren Flags flysch occur transitionally below and above the 180-ft upper Whitehouse fossiliferous deltaic red and green mudstone section. The delta was built to the southeast and east based on current directions in cross-bedded conglomeratic sandstone and limestone scour channels. Flutes on both Whitehouse and Barren graded sandstones indicate consistent longitudinal, southwest-flowing currents, perpendicular to the direction of delta-building, and approximately parallel and adjacent to the inferred geosynclinal margin. Therefore, the currents are unlikely to represent axial turbidity current flows. The regional slope probably dipped southeastward from the geosynclin l margin towards the axial portion. The graded sandstones may have been deposited in relatively shallow water from waning ocean bottom currents that flow southwest across the regional southeast paleoslope, rather than by gravity-controlled, down-slope turbidity currents.

MORRISON, CLOVERLY, AND SYKES MOUNTAIN FORMATIONS, NORTHERN BIGHORN BASIN, WYOMING AND MONTANA

Research Article| August 01, 1960 MORRISON, CLOVERLY, AND SYKES MOUNTAIN FORMATIONS, NORTHERN BIGHORN BASIN, WYOMING AND MONTANA RALPH MOBERLY, JR. RALPH MOBERLY, JR. UNIVERSITY OF HAWAII, HONOLULU, HAWAII Search for other works by this author on: GSW Google Scholar GSA Bulletin (1960) 71 (8): 1137–1176. https://doi.org/10.1130/0016-7606(1960)71[1137:MCASMF]2.0.CO;2 Article history received: 06 Jun 1958 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation RALPH MOBERLY; MORRISON, CLOVERLY, AND SYKES MOUNTAIN FORMATIONS, NORTHERN BIGHORN BASIN, WYOMING AND MONTANA. GSA Bulletin 1960;; 71 (8): 1137–1176. doi: https://doi.org/10.1130/0016-7606(1960)71[1137:MCASMF]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Morrison, Cloverly, and Sykes Mountain formations are the uppermost Jurassic and lowermost Cretaceous sedimentary rocks in the northern Bighorn Basin, Wyoming and Montana. Similar formations were deposited contemporaneously throughout most of the Western Interior.Most studies of nonmarine rocks have been in localities of more rapid sedimentation, whereas the rocks of this study accumulated slowly, under virtually atectonic conditions.The Morrison formation of the Bighorn Basin, as here restricted, includes the earliest-formed nonmarine sedimentary rocks of this sequence, conformably overlying the marine Sundance formation. The rocks are interlensed calcareous quartz sandstones, green mudstones and shales, and subordinate limestones, with locally conspicuous red-banded mudstones.Overlying the Morrison formation, generally with conformity, is the Cloverly formation, as redefined in this report. The lowest of its three members, here named the Little Sheep mudstone members, consists chiefly of bentonitic (montmorillonitic) mudstones in variegated shades of neutral gray, purple, olive, and dusky to pale red. Other typical lithologies include bentonites, cherts, coaly beds, calcareous nodules, and chert-pebble conglomeratic sandstones. The Pryor conglomerate member in the northernmost Bighorn Basin is characterized by black-chert pebbles and rests unconformably on the Morrison formation. Its beds are the stratigraphic equivalent of the mid-Little Sheep conglomeratic sandstones farther south. The upper member of the Cloverly formation, here named the Himes member, comprises three principal lithologies. Commonly at its base is olive-gray and reddish-brown clay-matrixed salt-and-pepper sandstone. Most of the member is variegated reddish- and yellowish-brown and gray kaolinitic claystone and mudstone, containing veinlets and hardpans of iron oxides. Clean quartz sandstones which filled fluvial channels are laced through the claystones.Disconformably overlying the Himes member are sandstones and thinly interbedded, rusty-brown–weathering siltstones, dark shales, and ironstones, here named the Sykes Mountain formation. The Sykes Mountain formation grades into the overlying marine Thermopolis shale.Distinction of stratigraphic units on a lithogenetic basis is believed to eliminate the confusion which existed in previous nomenclature of this sequence.Characteristic primary and secondary structures, clay, accessory, and authigenic minerals, and gross stratigraphic distribution aided the interpretation of the origin and history of these deposits. The Morrison formation accumulated in fluvial, lacustrine, and flood-plain environments from detritus derived chiefly from erosion of sedimentary rocks west of the present Bighorn Basin. The Little Sheep mudstone member and most of the Himes member of the Cloverly formation probably were formed authigenically in seasonal lakes and swamps from weathering of volcanic debris, with their different lithologies due to different drainage conditions and parent ash. The Pryor conglomerate member of the Cloverly formation and lenses of similar conglomeratic sandstones in the Little Sheep member were derived from reworked sedimentary rocks west of the depositional area. Channel-filling clean quartz sandstones of the Himes member were derived from an eastern sedimentary, and perhaps metamorphic, terrain. Thinly interbedded sandstones and shales of the Sykes Mountain formation are tidal-flat and other shallow-water beds deposited at the periphery of the transgressing Early Cretaceous sea.Slow deposition of these well-sorted and mature detrital sediments and close adjustment of authigenic minerals to prevailing environments depended largely on the stable tectonic conditions. During Cloverly time, very little aggradation except of volcanic debris took place, so that soils were formed and preserved. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Clay Minerals in the Morrison Formation on the Colorado Plateau

Clay Minerals in the Morrison Formation on the Colorado Plateau

The geology of the Llandovery district: Part II. the Northern Area

Summary The area described lies north-east of Llandovery and within about seven miles of that town; it is largely exposed, heather-clad upland. The adjoining area to the south was dealt with by the same author in a paper published in 1925. The three divisions (A) Lower, (B) Middle and (C) Upper Llandovery, established in the south, are recognized in the Northern Area, but here they vary greatly in thickness and some even disappear locally. Along the western boundary the Lower Llandovery rocks are faulted against Upper Bala mudstones with thin grits. Due east of the town only the lower part of the Lower Llandovery occurs between the Western Boundary Fault and the Upper Llandovery, but farther north, in the Crychan valley, the higher parts of the formation appear for a short distance. East of Noethgrug the whole subdivision is overstepped by the Upper Llandovery. The Middle Llandovery first appears in the Crychan valley about three miles northeast of the town, and after trending to the north and then the south disappears under the Upper Llandovery three miles east of the place where it first appears. North of these two points the subdivision is represented probably to its full thickness and in places yields many graptolites. The Upper Llandovery maintains its general characters through Cefn-y-gareg and Noethgrug, but near Craig-wyddon thinning sets in and within about three miles the main development is reduced to only 40 feet of Pentamerus oblongus sandstones. The uppermost part of the formation consists of green mudstones with some thin siliceous bands. The Upper Llandovery below these mudstones near Llandovery consists largely of greenish, sheared-looking mudstones but becomes more sandy to the north-east. It is significant that not only the Upper Llandovery but also the Middle and Lower Llandovery in the Noethgrug area develop coarse sandy and pebbly beds. At the extreme north-east of the district the base of the Upper Llandovery can be seen resting on Upper Bala mudstones. The structure of the area is relatively simple; to the east of the Western Boundary Fault the Lower Llandovery rocks dip with few exceptions very steeply, or are even vertical. In the succeeding Middle and Upper Llandovery of Gefn-y-gareg the dip lessens, and between Cefn-y-gareg and Noethgrug the beds turn over in an impressive pitching syncline. On Noethgrug the rocks dip west at moderate angles, but south of that region they turn over in a broad anticline with a southerly pitch. On the eastern limb of the anticline in the Craig-wyddon ridge they again become vertical. The core of the Noethgrug anticline is occupied by Upper Bala mudstones which are partially surrounded by a strong escarpment of Lower Llandovery rocks. The dips in the folds suggest a push from the north-west.

The geology of the Silurian rocks west and south of the Carneddau Range, Radnorshire

Summary An account is given of the geological succession from the Upper Llandovery to the lower part of the Lower Ludlow. The former group is developed in two distinct facies—an eastern facies of calcareous sandstones with Pentamerus oblongus , and a western facies of green mudstones and dark shales containing Monograptus crenulatus and other graptolites. The Wenlock rocks are dark graptolitic shales which have been divided into two sub-groups. They include the six graptolite zones erected by Dr. G. L. Elles in 1900. The Lower Ludlow rocks consist of shales with Monograptus nilssoni . In the Upper Wenlock and above the M. nilssoni shales there are important developments of slumped mudstones which have been mapped in detail. The area is a shallow syncline traversed by a series of powerful faults ranging mainly in the direction of the strike. Some of them behave as block faults. One fault appears to be a tear which has shifted earlier faults. Cleavage is sporadically developed.

The Petrography and Petrology of the Lower Cambrian Manganese Ore of West Merionethshire

The Cambrian manganese ore of the Ardudwy district of Merionethshire occurs interstratified in that series of rocks which locally forms the lowest Cambrian and which is known as the Harlech Grit series. This series crops out in a broad, irregularly oval, mountainous tract, with the long axis alined north and south. It extends from Barmouth in the south to within about one mile of Ffestiniog in the north and from the coast on the west to the Ganllwyd valley on the east. Ramsay (1881, p. 19) first described these rocks, but no attempt was made to classify the series until in 1893 Good-child grouped them as follows (Dewey and Dines 1923, p. 59):— 4. Upper Mudstones (Lingula Flags and Menevian) with Upper Manganese Bed at base. 3. Upper or Moelfre Grits. 2. Lower Mudstones; Lower Manganese Bed near base. 1. Lower Grits. He thus recognized two manganese horizons separated by at least 850 feet of rocks. Charles Lapworth and T. Stacey Wilson, recognizing only one ore bed, divided the Harlech Grit series of the Survey as follows (Andrew 1910, p. 161):— 5. Gamlan Shale group: grey, greyish green, and sometimes purple shales, slates and flags with occasional grit bands increasing in number eastward. 750–1200 feet. 4. Barmouth Grits: massive grits and conglomerates. 600 feet. 3. Hafotty or Manganese Shale group: grey and green mudstones with rare grits in west, becoming more frequent

Some Petrological Studies in the Harlech Grit Series of Merionethshire. III. The development of Pyrite in the Grits and Mudstones

In the Harlech Grit Series pyrite always occurs associated with rocks of practically all grades. It is, on the whole, of least importance in the grits, but even in these it becomes locally fairly abundant. Among the mudstones it occurs concentrated into layers, which are relatively persistent laterally. Immediately below the manganese-ore of the Manganese Shale Group, for example, there occurs a very widespread band of green mudstone which contains abundant pyrite crystals. Although its general characters are the same this band varies slightly, in detail when traced laterally and it is with these variations that the present paper is largely concerned. This band is usually 1 to 2 inches thick and is usually of dark green mudstone, though rarely it is of the normal blue-grey colour. The pyrite crystals vary from very minute to about ⅜ inch in size. In addition, pyrite occurrences from other rocks are described. The account is particularly concerned, not with the pyrite crystals themselves, but with zones of authigenous minerals which almost invariably surround them in these rocks.

A Fossiliferous Limestone associated with Ingletonian Beds at Horton-in-Ribblesdale, Yorkshire

T he oldest rocks of the Ribble valley have long been known in the area around Horton, and they have always been considered a continuation of the larger outcrop near Ingleton. The earlier writers included these beds as part of the ‘green slates and porphyry’ series, while in later times the name ‘Ingletonian’ has been given to this group of hard, green, felspathic grits and roughly-cleaved green mudstones. Opinions regarding the age of the Ingletonian fall into two groups. A. Sedgwick (1852, p. 35) , the officers of the Geological Survey ( Dakyns & others, 1890, p. 10 ), T. McKenny Hughes (1867, p. 253 & 1902, pp. 323, 328) , and, in more recent years, Mr. J. F. N. Green (1917, pp. 95-7) claimed that the Ingletonian belongs to some part of the Ordovician sequence— either to the Borrowdale Volcanic Series or to the beds which should come between the volcanics and the Coniston Limestone Series; while the other view, held by W. T. Aveline (in Goodchild, 1892, p. 299 ), Prof. J. E. Marr (1892, p. 104) , and Dr. R. H. Rastall (1906, p. 99) correlates the Ingletonian with some part of the Pre-Cambrian, such as the Longmyndian. The evidence for holding one view or the other rested mainly on the lithological characters of the rocks. In the main exposure near Ingleton there are continuous sections in the valley for several miles, but near Horton only isolated exposures occur in the river bed and in and near the great quarry at Horton station. The

Societies and Academies

LONDON. Geological Society, Mar. 18.—O. H. Schindewolf, On the septal development and the genotype of the coral genus Petraia Münster. The author, by showing that the genotype of Petraia is a synonym of Petraia radiata Münster, restricts the name to the Upper Silurian species. The Devonian species belong to Poĉta's genus Alleynia. Petraia, which is well characterised by its conical shape, deep calice, external ornamentation, arrangement of the septa, and, in normal specimens, by the absence of transverse tissue, has not been found outside Bavaria. W. B. R. King: A fossiliferous limestone associated with Ingletonian Beds at Horton-in-Ribblesdale, Yorkshire. The paper deals with an exposure of green felspathic grits with associated calcareous rocks in the railway cutting south of Horton-in-Ribblesdale station. The problems of general stratigraphy are discussed. There is much evidence of a general nature to suggest that although the limestone is undoubtedly of Ashgillian age, the grits with which it is associated must be considerably older. Calcareoits matter occurs in two forms in the cutting first, as the infilling between the grit blocks of a breccia, and secondly, as a crystalline fossiliferous limestone apparently inter-bedded with the grits. A detailed study of the limestone, however, shows that it is essentially of the same origin as the calcareous part of the breccia, since it contains angular fragments of grit and occasional flakes of roughly-cleaved green mudstone of a type exactly like the Ingletonian of the neighbourhood. The fossils show no signs of distortion by cleavage. It is suggested that this is another case of a ‘Neptunian dyke’.