V.—Note on some Pebbles in the Basal Conglomerate of the Cambrian at St. Davids

T. G. Bonney

doi:10.1017/s0016756800176459

V.—Note on some Pebbles in the Basal Conglomerate of the Cambrian at St. Davids

Geological Magazine ◽

10.1017/s0016756800176459 ◽

1889 ◽

Vol 6 (7) ◽

pp. 315-318 ◽

Cited By ~ 1

Author(s):

T. G. Bonney

Keyword(s):

Vein Quartz ◽

Basal Conglomerate ◽

Cambrian System

More than one kind of rock, as we learn from Dr. H. Hicks and other writers, occurs in the conglomerate which forms a well-marked base to the Cambrian system at St. Davids. Sometimes the pebbles are mainly vein quartz, sometimes felstone predominates, but occasionally, as in the neighbourhood of Nun's Chapel Bay, quartzites (using the term rather generally) are not uncommon. At one place, not far from a quartz-felsite dyke, these are rather large, occasionally about a foot in diameter. From this locality, while spending a few days at St. Davids in 1882, I brought away specimens of three of the most marked varieties of quartzite, of which I had slices prepared, thinking that as examples of rocks which were probably far from modern at the beginning of the Cambrian age, their structures might be instructive.

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Reinterpretation of the Aravalli basal conglomerate at Morchana, Udaipur district, Rajasthan, western India

Geological Magazine ◽

10.1017/s0016756800051128 ◽

1971 ◽

Vol 108 (2) ◽

pp. 111-114 ◽

Cited By ~ 11

Author(s):

K. Naha ◽

A. Majumdar

Keyword(s):

Western India ◽

Mica Schist ◽

Vein Quartz ◽

Basal Conglomerate ◽

Tectonic Mélange ◽

Banded Gneissic Complex

SummaryThe supposed Aravalli basal conglomerate near Morchana, considered to mark an erosional unconformity above the older Precambrian Banded Gneissic Complex in central Rajasthan, is a tectonic mélange in a terrain involved in superposed deformations. The supposed pebbles represent tectonic inclusions of various shapes, formed by isoclinal folding, stretching and disruption of concordant, pre- or early-kinematic vein quartz and rare pegmatite sheets in the Aravalli mica schist during the first folding.

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Facies Architecture and Sedimentary Structures in the drill cores of Uranium Bearing Sediments of Banganapalle Formation of Palnad Sub-basin, Guntur District, Andhra Pradesh

Indian Association of Sedimentologists ◽

10.51710/jias.v38i1.128 ◽

2021 ◽

Vol 38 (1) ◽

pp. 109-118

Author(s):

SHEKHAR GUPTA ◽

R V Singh ◽

Rahul Banerjee ◽

M B Verma

Keyword(s):

Andhra Pradesh ◽

Carbonaceous Matter ◽

Vein Quartz ◽

Sedimentary Structures ◽

The North ◽

Composition Variation ◽

Quartz Arenite ◽

Guntur District ◽

Basal Conglomerate ◽

Polymictic Conglomerate

The Banganapalle Formation, the lowest member of the Neoproterozoic Kurnool Group of rocks, resting over the basement granites, has been identified as the host rock for uranium in Koppunuru area in the western part of Palnad sub-basin. The uppermost arenite facies of the Banganapalle Formation is exposed on surface and shows only few bedform indicators like ripple marks, planer laminations etc. Down-hole lithological examinations on course of core drilling in Koppunuru and adjoining areas identified five recognizable lithofacies of Banganapalle Formation, viz. basal conglomerate unit, quartzite-shale intercalated facies, and two quartz arenite facies separated by a grey shale dominated argillaceous facies. The polymictic conglomerate, with unsorted grit to pebble size clasts of granite, shale, quartzite, vein quartz and dolerite indicate short distance transportation and derivation from nearby granitoids traversed by quartz reef/dolerite dykes. Cyclic repetitions of arenaceous and argillaceous sediments in Banganapalle lithocolumn above the basal conglomerates point to alternate rhythmic marine transgression and regression regimes. These units can also be discriminated based on their sedimentary texture, bedforms and several soft-sedimentary penecontemporaneous deformational structures (PCD) like load structure, convolute bedding/laminations, and slump structures such as micro-slips, gravity faults and folds. These syn-sedimentary structures clearly indicate perturbation and submergence of the basin contemporaneous to deposition. Cross-beds suggests change in current direction/intensity while bi-directional symmetrical ripples in outcrops of upper arenite facies suggests that the Banganapalle sediments are derived from the basement granitoids exposed to the north as well as upper Cuddapah sediments to its west. Overall, the sedimentary structures, textural and composition variation of the lithounits suggest deposition of these sediments in marginal marine, inter- to supra-tidal flat environment. The porous and permeable nature of the quartz arenite and the basal conglomerates and the presence of available reductants in the form of sulphides and carbonaceous matter make them the best suited loci for fluid movement and precipitation of uranium.

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The lower boundary of the Cambrian System in Taymyr

International Geology Review ◽

10.1080/00206818209467117 ◽

1979 ◽

Vol 21 (7) ◽

pp. 765-768

Author(s):

I. I. Kopfev ◽

V. V. Bezzubtsev ◽

V. A. Shipitsyn

Keyword(s):

Lower Boundary ◽

Cambrian System

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Changing perspectives on Cambrian chronostratigraphy and progress toward subdivision of the Cambrian system

Geosciences Journal ◽

10.1007/bf02910572 ◽

2005 ◽

Vol 9 (2) ◽

pp. 101-106 ◽

Cited By ~ 109

Author(s):

Loren E. Babeock ◽

Shanchi Peng ◽

Gerd Geyef ◽

John H. Shergold

Keyword(s):

Cambrian System

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Analysis of Sedimentary Facies Model - The Cretaceous Bottom Conglomerate of Xinjiang Junggar Basinludong Area as an Example

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.522-524.1289 ◽

2014 ◽

Vol 522-524 ◽

pp. 1289-1292

Author(s):

Bin Xiao ◽

Jun Li ◽

Yu Hua Fan

Keyword(s):

System Analysis ◽

Pattern Analysis ◽

Facies Analysis ◽

Sedimentary Facies ◽

Theory Method ◽

Sedimentary Structure ◽

Deposition Pattern ◽

Structure Feature ◽

Analysis Phase ◽

Basal Conglomerate

This paper aims to Cretaceous bottom conglomerate facies of Xinjiang Ludong area of China research to elucidate the deposition pattern analysis phase, as well as the use of methods. Methods first take logging combined with tectonic pattern and sedimentary background, division comparing in Ludong area of Cretaceous basal conglomerate unit. Secondly, the application of modern sedimentology theory, method, system analysis of lithologic characteristics of this area and sedimentary structure feature. According to the logging facies analysis, summarized the various sedimentary facies marks, distinguishing different sedimentary types, ultimately determine the sedimentary facies.

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A new eusuchian (Crocodylia) tooth from the Early or Middle Paleocene, with a description of the Early–Middle Paleocene boundary succession at Gemmas Allé, Copenhagen, Denmark

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-2014-62-02 ◽

2014 ◽

Vol 62 ◽

pp. 17-26

Author(s):

Daniela Schwarz Wings ◽

Jesper Milàn ◽

Palle Gravesen

Keyword(s):

Late Cretaceous ◽

Northern Europe ◽

Tooth Crown ◽

Southern Sweden ◽

Tooth Morphology ◽

Rounded Apex ◽

Southern Scandinavia ◽

Basal Conglomerate

A recently found crocodylian tooth crown from the basal conglomerate of the Middle Paleocene (Selandian) Lellinge Greensand Formation, differs morphologically from other finds of crocodylian teeth from the Paleocene of southern Scandinavia. The tooth is conical and blunt with a narrow rounded apex, and slightly curved along the axis of its length. The morphology of the tooth suggests it belongs to either the longirostrine eusuchian Aigialosuchus, which is known from the Campanian of southern Sweden, or to a member of the Alligatoridae which are the most common crocodylians in northern Europe in the Late Cretaceous. Gavialoid crocodylians, in particular Thoracosaurus which is known from the Danian limestome of the Limhamn quarry in southern Sweden and from the Faxe quarry in eastern Denmark, can be excluded because of their deviating tooth morphology. Regardless of its assignment, the tooth is interesting in a stratigraphic context as it demonstrates the existence of at least two crocodylian taxa in Scandinavia during the Early and Middle Paleocene.

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Palaeozoic studies in honour of Sir James Stubblefield

Geological Magazine ◽

10.1017/s0016756800033811 ◽

1981 ◽

Vol 118 (6) ◽

pp. 581-589 ◽

Cited By ~ 1

Author(s):

James Stubblefield

Keyword(s):

Royal College ◽

New Genus ◽

Science And Technology ◽

Field Work ◽

Imperial College ◽

Geological Survey ◽

Current Survey ◽

Lower Palaeozoic ◽

Cambrian System

Sir James was born on 6 September 1901 at Cambridge where he attended the Perse School. He received his geological education at Chelsea Polytechnic and the Royal College of Science. In 1923 he was appointed demonstrator in geology at the Imperial College of Science and Technology, London University, where he stayed until 1928; for his last two years there he also served as Warden at the pioneer Imperial College hostel. While at Imperial College he studied the Shineton Shales of the Wrekin district of Shropshire under the guidance of W. W. Watts and in collaboration with his life-long friend O. M. B. Bulman, and was awarded a Ph.D. in 1925. This work in Shropshire provided the stimulus for his continuing contribution on the Cambrian system and its faunas, and on trilobites of all ages. During this period he also recorded his observations on Tertiary crabs from Zanzibar, a group he was to return to in later years. In 1928 he obtained one of the two posts offered by the Geological Survey, being appointed Geologist. He undertook field work in the Dorking district as a prelude to an intended posting to the Survey office at York, but the death of G. W. Lee, then palaeontologist in Edinburgh, determined that Stubblefield should remain at the headquarters of the Survey at Jermyn Street in London. Internal transfers of the palaeontological staff left no member available to determine the fossils then accumulating from the current survey of the Shrewsbury district, and Stubblefield was asked by the Director to undertake this task because of his knowledge of the Lower Palaeozoic faunas of Shropshire. This transfer became long-term and thus began his association with, and eventual leadership of, the Palaeontological Department of the Survey, and secured the continuation of his notable contributions to palaeontology. The Shrewsbury commitment led to visits to the area during which new faunal horizons were discovered in the local Cambrian and Ordovician, including the Nemagraptus gracilis fauna from the Breidden Hills; other finds included the then earliest British eurypterid subsequently described by L. Størmer as the type of a new genus under the name of Brachyopterus stubblefieldi.

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Nature and evolution of metamorphic fluids associated with turbidite-hosted gold deposits: Hill End goldfield, NSW, Australia

Mineralogical Magazine ◽

10.1180/minmag.1993.057.388.06 ◽

1993 ◽

Vol 57 (388) ◽

pp. 423-436 ◽

Cited By ~ 11

Author(s):

P. K. Seccombe ◽

J. Ju ◽

A. S. Andrew ◽

B. L. Gulson ◽

K. J. Mizon

Keyword(s):

Lead Isotope ◽

Early Carboniferous ◽

Gold Deposits ◽

Source Rocks ◽

Gold Deposition ◽

Vein Quartz ◽

Sulphur Isotope ◽

Hydrous Minerals ◽

Vein Formation ◽

The Hill

AbstractThe Hill goldfield, NSW, Australia, is an example of a syntectonic, slate-belt gold deposit formed in a multiply deformed, Late Silurian slate-metagreywacke turbidite sequence. Gold is confined to bedding-parallel veins and discordant leader veins composed of as many as four generations of quartz, accompanied by phyllosilicates, carbonates and minor sulphides. Vein formation and gold deposition was apparently synchronous with Early Carboniferous metamorphism and deformation. Homogenisation temperatures (Th) for fluid inclusions in vein quartz demonstrate five groupings in the temperature intervals 350-280°C 280-250°C 250-190°C 190-150°C and 150-110°C corresponding to a variety of primary and secondary inclusions developed during four periods of vein quartz deposition under a generally declining temperature regime. Inclusion fluids are characterised by a low salinity of around 0.1 to 3.6 wt. % NaCl equivalent. The dominant gas phase present in the inclusion fluids varies from N2 in the early stages of the paragenesis, through CH 4 during the main episode of gold deposition, to CO2- rich fluids associated with late-stage mineralisation. δ18O values for vein quartz (range 15.1-17.1‰) and vein carbonate (range 11.3-13.4‰) are typical of metamorphic mineralisation. δD composition of hydrous minerals and inclusion fluids (range −53 to −138‰) suggest an influx of meteoric water in the later mineralising fluids. This conclusion is supported by δ13C data for vein calcite (range −2.5 to −9.7%0). δ34S composition of vein pyrrhotite and pyrite ranges from 6.9 to 7.8‰ early in the paragenesis, to lighter values (around 4.2 to 5.8%0) accompanying late gold deposition from more oxidising fluids. Sulphur isotope data imply a sulphur source from underlying turbidites and an increase in fluid oxidation state during mineralisation . Lead isotope measurements on vein pyrite, arseno py rite, galena and gold are characterised by two isotope populations with 207Pb/206Pb ratios of 0.862 and 0.860, which define two discrete mineralising events during vein formation. Consistency between data from vein minerals and lead isotope signatures for potential source rocks indicate that lead was derived from the sedimentary pile.

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