Academic literature on the topic 'Glacigene sedimentary rocks'

The 3-27 m-thick cap carbonate overlying "Marinoan" Ice Brook Formation glacigene sediments and Keele Formation carbonate and terrigenous clastic rocks consists of two distinctive stratigraphic units. A lower, splintery, buff-weathering, microcrystalline dolostone of extensive lateral uniformity comprises mm-laminated peloidal sediment with local, low-angle, hummocky-like cross-stratification, micro-ridges, and synsedimentary tepees, all elongated perpendicular to depositional strike. This dolostone is unconformably overlain by an upper limestone that exhibits pronounced facies variation from inboard peloidal lime grainstone and mudstone to shelf-edge cementstone to outboard lime wackestone and mudstone. Calcite cementstones range from isolated crystal fans in laminated limestone to huge, decimetre-scale crystal arrays, to hemispherical and elongate crystal stromatolites wholly composed of acicular crystals that form decametre-scale reeflike structures. Crystal stromatolites are precipitates and replaced microbiolites that constructed biostromes and bioherms, like those on many flat-topped, reef-rimmed platforms. The calcite crystals have all the physical and chemical attributes of neomorphosed aragonite. This aragonite extensively replaced sediment and microbiolite just below the sea floor and grew upward into the overlying water column. Such interpreted massive synsedimentary replacement is rare in geological history and attests to the highly saturated state of the immediate postglacial ocean. All sediment is interpreted to have been CaCO3 originally. Low and constant δ18O values reflect diagenetic modification of these carbonates, although chemical attributes, such as Sr and C isotopes in some lithologies, are near pristine. Lower dolostones, virtually identical to most other coeval Marinoan caps worldwide, were part of a global precipitation event of remarkable similarity. Upper limestones are a more local phenomenon, deposited during sea-level rise in an aragonitic sea returning to equilibrium after global glaciation. Low 87Sr/86Sr ratios and varying δ13C values with carbonate sedimentary facies indicate that both units must have formed relatively rapidly, prior to significant fluvioglacial runoff, or that the influence of this runoff on the chemistry of seawater along continental shelves was minimal. The cap carbonate is thus interpreted to have formed in two steps: (1) during initial marine ice melting accompanied by oceanic overturn and upwelling, preceding continental margin rebound, and (2) during initial stages of sea-level rise accompanying continental deglaciation. While confirming brief, but extensive, carbonate precipitation from an ocean highly perturbed by global glaciation, the rocks also suggest that this event did not permanently affect either late Neoproterozoic ocean chemistry or the contained marine biosphere.

Abstract. In the late 19th century, a regional map of Nueva Granada (present-day Colombia, Panama and parts of Venezuela and Ecuador) was published by German botanist and geologist Hermann Karsten (1817–1908). Karsten's work was incorporated by Agustín Codazzi (1793–1859), an Italian who emigrated to Venezuela and Colombia to serve as a government cartographer and geographer, in his popular Atlas geográfico e histórico de la Republica de Colombia (1889). Geologic mapping and most observations provided in this 1889 atlas were taken from Karsten's Géologie de l'ancienne Colombie bolivarienne: Vénézuela, Nouvelle-Grenade et Ecuador (1886), as cited by Manual Paz and/or Felipe Pérez, who edited this edition of the atlas. Karsten defined four epochs in Earth history: Primera – without life – primary crystalline rocks, Segunda – with only marine life – chiefly sedimentary rocks, Tercera – with terrestrial quadrupeds and fresh water life forms life – chiefly sedimentary rocks, and Cuarta – mankind appears, includes diluvial (glacigenic) and post-diluvial terranes. He noted that Colombia is composed of chiefly of Quaternary, Tertiary and Cretaceous plutonic, volcanic and sedimentary rocks, and that Earth's internal heat (calor central) accounted, by escape of inner gases, for volcanism, seismicity and uplift of mountains. Karsten's regional mapping and interpretation thus constitutes the primary source and ultimate pioneering geologic research.

Geochemical and magnetic data from glacigenic sediments can be useful indicators of past environments and climate. In this paper, the results of X-ray fluorescence (XRF) and rock magnetic analyses are presented for samples from the Pagodroma Group, an assemblage of pre-Quaternary glacimarine sediments preserved as remnants along the raised flanks of the Lambert Graben, Prince Charles Mountains, East Antarctica. Samples were obtained from four formations: Mount Johnston, Battye Glacier, Fisher Bench and Bardin Bluffs, which range in age from late Oligocene or early Miocene through to Pliocene or early Pleistocene. Principal component analysis of the XRF data indicates the occurrence of two main element assemblages, which we infer are determined by the presence in the Bardin Bluffs formation of a significant component derived from Permo–Triassic sedimentary rocks of the Amery Group. Calculation of chemical indices of alteration suggests that the values reflect provenance differences rather than the syndepositional weathering environment. Multidomain ferrimagnetic grains mainly dominate the magnetic mineral assemblages of the samples, probably magnetite, with varying concentrations of high coercivity material, probably hematite.

AbstractThe Neoproterozoic Hedmark Basin in the Caledonides of South Norway was formed at the western margin of the continent Baltica by rifting 750–600 Ma ago. The margin was destroyed in the Caledonian Orogeny and sedimentary basins translated eastwards. This study uses provenance analysis to map the crustal architecture of the pre-Caledonian SW Baltican margin. Conglomerate clasts and sandstones were sampled from submarine fan, alluvial fan and terrestrial glacigenic sedimentary rocks. Samples were analysed for U–Pb isotopes and clast samples additionally for Lu–Hf isotopes. The clasts are mainly granitesc. 960 Ma and 1680 Ma old, coeval with the Sveconorwegian Orogeny and formation of the Palaeoproterozoic Transscandinavian Igneous Belt (TIB). Mesoproterozoic (Sveconorwegian) ages are abundant in the western part of the basin, whereas Palaeoproterozoic ages are common in the east. Lu–Hf isotopes support crustally contaminated source for all clasts linking them to Fennoscandia. Detrital zircon ages of the sandstones can be matched with those from the granitic clasts except for ages within the range 1200–1500 Ma. These ages are typically found in the present-day Telemark, SW Norway. The sandstones and conglomerate clasts in the western part of the Hedmark Basin were sourced from the Sveconorwegian domain in the present SW Norway or its continuation to the present-day NW. The conglomerate clasts in the eastern part of the Hedmark Basin were sourced mainly from the TIB domain or its northwesterly continuation. The Hedmark Basin was initiated within the boundary of two domains in the basement: the TIB and the Sveconorwegian domains.

Pleistocene sediments collected in north-central Alberta, Canada, were subsampled and studied for paleomagnetic remanence characteristics. A magnetostratigraphy has been established for sediments previously assumed to represent multiple continental (Laurentide) glaciations but for which no geochronology was available. Based on the Quaternary record elsewhere in Alberta and Saskatchewan, it was thought that some of these sediments were deposited during pre-late Wisconsinan glaciations. The Quaternary sedimentary successions of north-central Alberta have a thickness up to 300 m within buried valleys and are composed of diamicts interbedded with glaciolacustrine and outwash sediments. Most of the sampled units are not accessible from outcrop, and their sedimentology and stratigraphy is derived from core data only. In 4 of 16 borecores sampled to date, diamict that correlates with the Bronson Lake Formation till is reversely magnetized, indicating an Early Pleistocene age. This formation is underlain by either Empress Formation sediments or Colorado Group shale, and is overlain by one or more normally magnetized glacigenic sedimentary units of the Bonnyville, Marie Creek, and Grand Centre formations, respectively. This new record of Early Pleistocene glaciation in north-central Alberta places the westernmost extent of earliest Laurentide ice at least 300 km farther west than its previously established limit in the Saskatoon and Regina regions of the Canadian Interior Plains, but still to the east of the maximum extent of the Late Wisconsinan (Late Pleistocene) Laurentide Ice Sheet, which extended into the foothills of the Alberta and Montana Rocky Mountains.

Abstract Tandem in situ and isotope dilution U-Pb analysis of zircons from pyroclastic volcanic rocks and both glacial and non-glacial sedimentary strata of the Pocatello Formation (Idaho, northwestern USA) provides new age constraints on Cryogenian glaciation in the North American Cordillera. Two dacitic tuffs sampled within glacigenic strata of the lower diamictite interval of the Scout Mountain Member yield high-precision chemical abrasion isotope dilution U-Pb zircon eruption and depositional ages of 696.43 ± 0.21 and 695.17 ± 0.20 Ma. When supplemented by a new high-precision detrital zircon maximum depositional age of ≤670 Ma for shoreface and offshore sandstones unconformably overlying the lower diamictite, these data are consistent with correlation of the lower diamictite to the early Cryogenian (ca. 717–660 Ma) Sturtian glaciation. These 670–675 Ma zircons persist in beds above the upper diamictite and cap dolostone units, up to and including a purported “reworked fallout tuff,” which we instead conclude provides only a maximum depositional age of ≤673 Ma from epiclastic volcanic detritus. Rare detrital zircons as young as 658 Ma provide a maximum depositional age for the upper diamictite and overlying cap dolostone units. This new geochronological framework supports litho- and chemostratigraphic correlations of the lower and upper diamictite intervals of the Scout Mountain Member of the Pocatello Formation with the Sturtian (716–660 Ma) and Marinoan (≤650–635 Ma) low-latitude glaciations, respectively. The Pocatello Formation thus contains a more complete record of Cryogenian glaciations than previously postulated.

The Žulová Upland is composed of granitoids of the Žulová batholith with relicts of Pleistocene (Elsterian) continental glaciation sediments. The investigated outcrop represents development of glacigenic sediments on rugged topography of the Žulová Upland. Investigated locality is situated on a hill located on the northern margin of the Žulová Upland. It is located near Štachlovice, local part of the Vidnava town. The exposed part of the hilltop reveals a preglacial basement covered by glacigenic sediments. The facies analysis and gravel petrology analysis of clasts with fraction 16–64 mm in b-axis were undertaken on the walls of the outcrop. The Georadar (GPR, Ground penetrating radar) was used to investigate the sedimentary landform and its relation to the basement. The granitoid basement is in places formed by elevations covered by glacigenic sediments. The height of elevation reaches 350 cmin outcrop, or ca ~400 cm according to the GPR survey. The glacitectonite, formed on the gentle side of elevation, is composed of angular blocks of granitoids of the Žulová batholith, diamicton, sand, gravel and deformed glacifluvial sand. The glacitectonite was deposited during the advancement of the continental glacier. The original subglacial cavity is enclosed by a steep side of the elevation. This cavity is filled by foreset body composed of stratified sand and gravel and nonstratified gravelly sand, gravel and diamicton. The cavity was filled by high-density turbidity currents and debris flow in subaqueous-subaerial environment. The infill of the cavity reaches ~400 cm in thickness according to the GPR survey. The cavity was filled during deglaciation in subglacial environment. The glacitectonite underlies the diamicton (supraglacial till) that was deposited as a debris flow during the retreat of the continental glacier. Unsorted gravel overlaps with erosional base the infill of the cavity, this gravel has a huge extent according to the GPR survey. This sediment represents the environment of terminoglacial stream. Gravel material of all types of glacigenic sediments is mainly composed of rocks from the Rychleby Mts. (amphibolites, Gierałtow orthogneiss, other diverse gneisses, quartzites, mica schist),quartz, and Nordic and Polish rocks. Subglacial sediments contain clasts of amphibolites (~40 %), on the other hand supraglacial and terminoglacial sediments are more polymict. Dominant subrounded shape (~60–70 %) of clasts and composition of this material indicates its origin in preglacial fluvial sediments. These fluvial sediments were deposited by river flowing from the Rychleby Mts. towards their northern foreland. The locality represents preglacial elevation of bedrock, which was glacitectonically deformed during the glaciation. Lots of different types of sediments (sub-, supra-, and terminoglacial) were deposited around the elevation during deglaciation period. The elevation was completely buried by these sediments. Deposition of these sediments was related with morphology of the elevation of bedrock. Formation of these sediments took place in environment analogous to environment of part bedrock/part till drumlin (Stokes et al. 2011).

The majority of southern Australia was covered in ice during the Gondwanan Permo-Carboniferous glaciation. Glacigene sequences associated with this event are preserved within basins including the Late Palaeozoic sediments of the Arckaringa and Troubridge basins in South Australia. In this study, detailed sedimentology, geochronology and geochemistry of these sediments is used to inform an improved palaeogeographic reconstruction of South Australia during the late Palaeozoic and to understand background geochemistry relevant to their use as geochemical exploration media. Diamictite units with rounded to angular, locally-derived clasts are observed throughout the Troubridge Basin and the south Arckaringa Basin. These are consistent with deposition by ice tongues and icesheets. Diamictite units with subrounded to rounded clasts with both locally- and distally-derived clasts are observed in the eastern margin Arckaringa Basin. These are consistent with sedimentary rocks deposited by valley glaciers. Alternating clay and sandstone beds with lesser diamictite beds are observed in discrete exposures in the Troubridge Basin. These are consistent with a glacial environment where meltwater streams have alternating energy and sediment load. This is due to the periodic melting of the ice mass which fed into glacial lakes. The increasing frequency of diamictite beds up-sequence is indicative of the rapid retreat and melting of the ice mass. Massive to bedded, green glaciomarine clays observed in the Troubridge Basin are consistent with sedimentary rocks deposited in a transitional glacial to marine to deepening glaciomarine setting. Sedimentary rocks deposited during the marine regression are interbedded with increasingly fluvial sedimentary rocks suggesting that freshwater streams were active during the waning stages of the regression. The resulting terrestrial environment consisted of alternating fluvial and lacustrine environment with intermittent formation of coal swamps. Alternating clay and sandstone beds with minor carbonaceous beds are observed in the upper succession of the Arckaringa Basin. These are consistent with sedimentary rocks deposited in an environment where post-glacial isostatic rebound causes alternating fluvial and lacustrine conditions. Zircon provenance spectra of the glacigene sedimentary rocks of the Troubridge Basin are dominated by ages between ca 500 to 600 Ma. These ages correlate with proximal rock packages of the Kanmantoo Group (Adelaide Rift Complex) and the Transantarctic Mountains of Antarctica. These sources are likely from sources adjacent to and from the south which is consistent with deposition via an icesheet and ice tongue. The zircon provenance spectra for the glacigene sedimentary rocks of the Arckaringa Basin are dominated by ages of ca 900 to 1200 Ma and ca 1700 to 1900 Ma. These ages are typical of rocks from the nearby Adelaide Rift Complex and the Gawler Craton as well as the distal Kanmantoo Group, Transantarctic Mountains, Musgrave Province and Arunta Region. These sources are likely from adjacent highlands and consistent with being deposited via valley glaciers formed in nearby alpine glacial systems. Major and trace element geochemistry of the minimally weathered clay and silt packages interbedded with diamictite in the Troubridge and Arckaringa basins are similar to PAAS and likely sourced from of the Kanmantoo Group. The depositional setting of the glacigene sediment is shown in SiO2:Al2O3 ratios. High silica end members represent sand-rich lithologies and high Al end members represent clay-rich lithologies. The Al-rich end members include clay matrix diamictites that are most likely the result of glacial deposition (rock flour + clasts). The Si-rich end members represent lithologies where fluvial processes removed the fine-grained clay-rich component. The complexity of the observed geochemical trends and the influence of weathering on the concentration of potential mineral exploration pathfinder (trace) elements highlights the necessity of understanding depositional and post-depositional influences on geochemistry. Weathering processes largely control the major and trace element geochemistry of weathered and indurated glacigene sedimentary rocks. These weathering processes include terraneous weathering (carbonate, sulphate and dolomite), ferruginous weathering and kaolinitic weathering. The sedimentology, geochronology and geochemistry of the late Palaeozoic glacigene sedimentary rocks of the Troubridge and Arckaringa basins are used to interpret a three-stage model of evolution of the late Palaeozoic glaciation. Stage 1: Glacial advance (late Palaeozoic). During the Permo-Carboniferous glaciation, the South Australian landscape was dominated by both continental and alpine glaciation. The continental ice sheet spread rapidly north from Antarctica into central South Australia, extending to southern margin of the Arckaringa Basin at the glacial maximum at the Asselian. Ice tongues at the front of the ice sheet scoured, eroded and polished the exposed landscape, forming U-shaped valleys and polished, glaciated pavements. At paleolatitudes north of the continental icesheet alpine glaciers occupied the highlands and valley glaciers transported debris into lowlying depocentres adjacent to the highlands. Stage 2: Glacial retreat and marine transgression (Sakmarian). The ice sheet rapidly melted and retreated from northern South Australia shedding debris into the Troubridge Basin. Melting slowed as it retreated further south. The retreat of the ice mass from northern South Australia opened a seaway into which marine waters entered from the west initiating a marine transgression in northern South Australia. When the marine transgression was at its maximum most of South Australia was inundated with only the eastern Gawler Craton Highlands remaining above seawater. Stage 3: Post-glacial isostatic rebound (late Sakmarian to early Artinskian). During this time the seaway contracted toward the south (Troubridge Basin) and there was a transition to fluviolacustrine conditions in the north (Arckaringa Basin).
Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2018