Sedimentation associated with glaciovolcanism: a review

Three discrete categories of sedimentary deposits are associated with glaciovolcanism: englacial cavity, jökulhlaup and lahar. Englacial cavity deposits are found in water-filled chambers in the lee of active glaciovolcanoes or at a locus of enhanced geothermal heat flux. The cavities provide a depocentre for the accumulation of debris, either abundant fresh juvenile debris with sparse dropstones (associated with active glaciovolcanism) or polymict basal glacial debris in which dropstones are abundant (associated with geothermal hot spots). Described examples are uncommon. By contrast, volcanogenic jökulhlaup deposits are abundant, mainly in Iceland, where they form extensive sandar sequences associated with ice-covered volcanoes. Jökulhlaups form as a result of the sudden subglacial discharge of stored meltwater. Analogous deposits known as glaciovolcanic sheet-like sequences represent the ultra-proximal lateral equivalents deposited under the ice. Glaciovolcanic lahars are associated with ice-capped volcanoes. They form as a result of explosive eruptions through relatively thin ice or following dome collapse, and they trigger mainly supraglacial rather than subglacial meltwater escape. Sediment transport and depositional processes are similar in jökulhaups and lahars and are dominated by debris flow and hyperconcentrated or supercritical flow modes during the main flood stage, although the proportions of the principal lithofacies are different.

Trends and Composition—A Sedimentological-Chemical-Mineralogical Approach to Constrain the Origin of Quaternary Deposits and Landforms—From a Review to a Manual

In this study, six basic Quaternary landform series (LFS) and their sedimentary deposits (LFS1 aeolian, LFS 2.1 to 2.2 mass wasting, LFS 3 cryogenic-glacial, LFS 4.1 to 4.6 fluvial, LFS 5.1 to 5.2 coastal-marine, LFS 6.1 to 6.3 lacustrine) are subdivided into subtypes and examined with regard to their sedimentological parameters and their mineralogical and chemical compositions. Emphasis is placed on the textural (related to transport and deposition), compositional (sediment load/weight, Eh and pH) and geodynamic maturity of the sedimentary deposits which are influenced by the parent lithology and bedrock tectonic and by the climate during the last 2 Ma. To constrain the development of the LFS and their sediments, composite trend-line diagrams are designed combining sedimentological (x-axis) and chemical/mineralogical dataset (y-axis): (1) sorting vs. heavy mineral content; (2) sphericity of grains vs. silica/carbonate contents; and (3) median vs. Ti/Fe ratios. In addition, the x-y plots showing the log SiO2/Al2O3 vs. log Na2O/K2O are amended by a dataset of the three most common clay minerals, i.e., kaolinite-, mica-, and smectite-group clay minerals. Such joint sedimentological-chemical-mineralogical investigations focused on the depositional environment of unconsolidated clastic sediments of Quaternary age can be used to describe the economic geology and environmental geology of mineral deposits in the pre-Quaternary sedimentary series according to the phrase: “The Present is the key to the Past”. Both trend diagrams and compositional x-y plots can contribute to constraining the development of the full transect of landform series from the fluvial incision and slope retreat to reef islands fringing the coastal zone towards the open sea as far as they are built up of clastic sedimentary deposits enriched in siliceous and/or carbonate minerals. Climate zonation and crustal maturity are the exogenous and endogenous “drivers”, as can be deduced from the compositional (mineralogy and chemistry) and physical (transport and deposition) variations observed in the Quaternary sediments. The current study bridges the gap between a review only based on literature and a hybrid manual generated by practical field studies devoted to applied geosciences in economic and environmental geology (“E & E issue”).

An Upper Ediacaran Glacial Period in Cadomia: the Granville tillite (Armorican Massif) – sedimentology, geochronology and provenance

In the Cadomian orogenic belt a package of glacigenic sedimentary deposits have been recently described in the Armorican Massif (Normandy, France). The Granville Tillite Member, the middle part of the upper Granville Formation, is late Ediacaran in age. Maximum depositional ages of the pre- and syn-glacial sedimentary deposits obtained by LA-ICP-MS U–Pb detrital zircon dating indicate a maximum age of 561 ± 3 Ma. Combined with geochronological data on the previously described glacial deposits in Cadomia, West Africa, Arabia and Iran, the Granville Tillite Member appears to represent an Upper Ediacaran Glacial Period in northern peri-Gondwana, clearly younger than the c. 580 Ma old Gaskiers glaciation. Detailed mapping and analysis of the depositional regime of two sections near the city of Granville are indicative of two independent glaciomarine lower and upper tillite deposits separated by a distinct conglomeratic marker horizon, evidently a massive gravel beach horizon deposited during an interglacial stage. Age spectra of detrital zircon U–Pb ages constrain the palaeogeographical position of the upper Granville Formation to the periphery of the West African Craton. Post-Gaskiers aged glaciations in Cadomia and in West Africa should be grouped into an Upper Ediacaran Glacial Period dated at c. 565 Ma. This glacial period seems not to be related to the negative δ13C Shuram–Wonoka anomaly. Sedimentary deposits formed during the Upper Ediacaran Glacial Period show a scattered distribution along the marginal orogens of the Gondwana supercontinent independent of palaeolatitude and are coupled most likely to contemporaneous orogenic processes and uplift.

Cenozoic evolution of the Campbell Plateau, Subantarctic New Zealand: Insights from sub-bottom profile data

<p>The Campbell Plateau represents ~30% of the submerged continent of Zealandia and represents part of the Gondwana super-continent that began to break-up ~98Ma. The focus of this MSc thesis is to use sub-bottom, profile data collected in 2017 and 2018 from Campbell Plateau to improve our understanding of the Cenozoic evolution of the region. The sub-bottom profiles show a rugged basement overlain by a variety of sedimentary sequences and subsurface features such as volcanoes, onlap, and downlap surfaces as well as multiple unconformities that can be traced throughout the Cenozoic (65Ma). The sub-bottom profiles are compared to 2 drill cores; Ocean Drilling Program (ODP) site 1120 on the eastern side of the plateau and Deep Sea Drilling Program (DSDP) site 277 in the south. These drill cores indicate that the lithology from the Cretaceous onwards is predominantly biogenic calcareous sandstone and mudstone, which changes to nannofossil-rich oozes in the Miocene and foraminiferal oozes and nannofossil oozes dated early to late Pleistocene. The northern plateau appears to be relatively quiescent with thin, relatively uniform strata, only influenced by small reverse faults. Sedimentary deposits such as wedges and contourites are also evident in the central and north-western part of the study area. The southern plateau appears to be have been highly dynamic with onlap/downlap surfaces, interpreted as current scours, and erosional surfaces. There is a plateau-wide unconformity during the Pliocene, as derived from the nannofossils of the ODP1120 drill core, which appears to have been a large-scale erosional event. The Southern Ocean circulation, dominated by Antarctic Circumpolar Current, the Subtropical Front, and local wind-driven currents, are the main drivers of these lithological changes and plateau-wide sedimentological structures. Previous interpretations of the sub-surface structure of the plateau are seen to be invalid in relation to this study, with the sub-surface seen to be relatively undeformed with only minor reverse faulting present. Areas of possible uplifted basement seen near Campbell Island also indicate that the Campbell Plateau has been through substantial erosion and deformation since its’ separation from Gondwana ~98Ma and movement to its modern-day position.</p>

Cenozoic evolution of the Campbell Plateau, Subantarctic New Zealand: Insights from sub-bottom profile data

<p>The Campbell Plateau represents ~30% of the submerged continent of Zealandia and represents part of the Gondwana super-continent that began to break-up ~98Ma. The focus of this MSc thesis is to use sub-bottom, profile data collected in 2017 and 2018 from Campbell Plateau to improve our understanding of the Cenozoic evolution of the region. The sub-bottom profiles show a rugged basement overlain by a variety of sedimentary sequences and subsurface features such as volcanoes, onlap, and downlap surfaces as well as multiple unconformities that can be traced throughout the Cenozoic (65Ma). The sub-bottom profiles are compared to 2 drill cores; Ocean Drilling Program (ODP) site 1120 on the eastern side of the plateau and Deep Sea Drilling Program (DSDP) site 277 in the south. These drill cores indicate that the lithology from the Cretaceous onwards is predominantly biogenic calcareous sandstone and mudstone, which changes to nannofossil-rich oozes in the Miocene and foraminiferal oozes and nannofossil oozes dated early to late Pleistocene. The northern plateau appears to be relatively quiescent with thin, relatively uniform strata, only influenced by small reverse faults. Sedimentary deposits such as wedges and contourites are also evident in the central and north-western part of the study area. The southern plateau appears to be have been highly dynamic with onlap/downlap surfaces, interpreted as current scours, and erosional surfaces. There is a plateau-wide unconformity during the Pliocene, as derived from the nannofossils of the ODP1120 drill core, which appears to have been a large-scale erosional event. The Southern Ocean circulation, dominated by Antarctic Circumpolar Current, the Subtropical Front, and local wind-driven currents, are the main drivers of these lithological changes and plateau-wide sedimentological structures. Previous interpretations of the sub-surface structure of the plateau are seen to be invalid in relation to this study, with the sub-surface seen to be relatively undeformed with only minor reverse faulting present. Areas of possible uplifted basement seen near Campbell Island also indicate that the Campbell Plateau has been through substantial erosion and deformation since its’ separation from Gondwana ~98Ma and movement to its modern-day position.</p>

Increasing the productivity of water in takein water-containing crystalline rocks by increasing their fracture by an explosion

Global warming, which has been observed in the world and Ukraine in particular in recent decades, may lead to a decrease in surface and groundwater. In addition, the high level of groundwater pollution and the policy of water purification is a matter of concern. Thus, the question of finding additional and alternative sources of drinking water today is highly urgent. A significant percentage of prospecting works of the last century was devoted to discovering the groundwater fields in fractured crystalline rocks of the Ukrainian Shield. As a rule, the productivity of wells of these formations did not have high flow rates, so even now, mostly the aquifers in sedimentary deposits have been exploited. The low productivity of most wells in water-bearing fractured rocks is associated with the unknown degree of fracturing of the crystalline massif: it is difficult to determine the pathways of groundwater inflow into the fracture system and, accordingly, it is not easy to justify the exploitable groundwater reserves. In this paper, using the groundwater flow model of the Zhashkiv groundwater deposit, it is considered an increase of the productivity of water intake wells in the water-bearing crystalline rocks due to the increasing degree of their fracturing by an explosion. Thus, in hydrogeology, this technique is known when trying to increase the permeability in the near-borehole space, but as a method of artificial recharge of aquiferous crystalline rocks is used very rarely. The paper also examines typical water intakes conditions in fractured crystalline water-bearing rocks, which can be recommended for increasing their productivity by the blasting method. The results indicate that an artificial increase in fracturing degree can have a significant effect on increasing the productivity of water intakes. The basic methods of using explosives, as an example of an artificial increase in fracturing degree, in solving hydrogeological problems and the mechanisms of fractures’ formation during the action of blasting are considered.

Geochronology, geochemistry and tectonic implications of early Carboniferous plutons in the southwestern Alxa Block

The southeastern Central Asian Orogenic Belt (CAOB) records the assembly process between several micro-continental blocks and the North China Craton (NCC), with the consumption of the Paleo-Asian Ocean (PAO), but whether the S-wards subduction of the PAO beneath the northern NCC was ongoing during Carboniferous–Permian time is still being debated. A key issue to resolve this controversy is whether the Carboniferous magmatism in the northern NCC was continental arc magmatism. The Alxa Block is the western segment of the northern NCC and contiguous to the southeastern CAOB, and their Carboniferous–Permian magmatism could have occurred in similar tectonic settings. In this contribution, new zircon U–Pb ages, elemental geochemistry and Sr–Nd isotopic analyses are presented for three early Carboniferous granitic plutons in the southwestern Alxa Block. Two newly identified aluminous A-type granites, an alkali-feldspar granite (331.6 ± 1.6 Ma) and a monzogranite (331.8 ± 1.7 Ma), exhibit juvenile and radiogenic Sr–Nd isotopic features, respectively. Although a granodiorite (326.2 ± 6.6 Ma) is characterized by high Sr/Y ratios (97.4–139.9), which is generally treated as an adikitic feature, this sample has highly radiogenic Sr–Nd isotopes and displays significantly higher K2O/Na2O ratios than typical adakites. These three granites were probably derived from the partial melting of Precambrian continental crustal sources heated by upwelling asthenosphere in lithospheric extensional setting. Regionally, both the Alxa Block and the southeastern CAOB are characterized by the formation of early Carboniferous extension-related magmatic rocks but lack coeval sedimentary deposits, suggesting a uniform lithospheric extensional setting rather than a simple continental arc.

Sandy soils of forest landscapes of the Amur-Zeya Plain

Historically, soils of the Cambisol group have been recognized as zonal soils of the Upper Amur Basin Region. However, the wide distribution in the territory of the Amur-Zeya Plain of forest soils of light granulometric composition that were formed on loose sedimentary deposits makes it possible to identify an area of Arenosols and Podzols, for the first time described within the study area. The common features in the researched soils are a well-structured thin humus horizon and quartzfeldsparic mineralogical composition causing low intensity of the processes of weathering and metamorphism of mineral substance. The initial stages of biochemical weathering of mineral matter are diagnosed in soils of the Humic Arenosol subgroup. The most intensive processes of weathering and metamorphism of mineral matter are diagnosed in the middle horizons of the Rubic Arenosol group, which is associated with the formation of seasonal frost and the associated cycles of freezing-thawing of the soil profile. In the soils of the Entic Podzol subgroup, the process of iron illuviation is diagnosed, with formation of the maximum accumulation in the lower part of the soil profile at the boundary with the soil-forming rock. Keywords: FOREST SOILS, NEOGENIC SANDS, SOIL MORPHOLOGY, THE UPPER AMUR BASIN REGION

GEOQUÍMICA E PETROGRAFIA DE DEPÓSITOS QUATERNÁRIOS DA PORÇÃO SW DA PRAIA BRAVA, ARMAÇÃO DOS BÚZIOS, RJ, BRASIL: EDFRX E DIFRAÇÃO A LASER

Resumo: Este artigo apresenta os dados geoquímicos e petrográficos de sedimentos praiais da região SW da Praia Brava (PB) em Armação dos Búzios-RJ. Buscamos discutir os processos de intemperismo químico e proveniência, bem como, analisar o ambiente geoquímico e a sua relação com as fontes autóctones. Neste estudo foram utilizadas análises petrográficas, parâmetros texturais na distribuição de partículas, geoquímica e estatística com auxílio de Laser Difraction e Fluorescência de Raios-X com Energia Dispersiva. Os sedimentos estudados são compostos essencialmente de granadas, biotita, piroxênio (diopsídio e augita?), epidoto, monazita, hornblenda, ilmenita, zircão, rutilo, titanita, silimanita, cianita, além de quartzo. Os sedimentos investigados são reflexo dos litotipos encontrados regionalmente, indicando possivelmente uma forte correlação entre as rochas-fonte e os depósitos sedimentares. O ambiente de oxirredução é demarcado pela presença de óxidos de Fe, provavelmente hematita. O índice de alteração calculado suporta um grau moderado, onde micas são preservadas, totalmente ou em partes. Palavras-Chave: Sedimentos Inconsolidados; Depósitos Praiais; Intemperismo Químico. GEOCHEMISTRY AND PETROGRAPHY OF QUATERNARY DEPOSITS FROM SW OF PRAIA BRAVA BEACH, ARMAÇÃO DOS BÚZIOS, RJ, BRAZIL: EDFRX AND LASER DIFRACTION Abstract: This article presents the geochemical and petrographic data of beach sediments from the SW region of Praia Brava (PB) in Armação dos Búzios-RJ. We seek to discuss the processes of chemical weathering and provenance, as well as to analyze the geochemical environment and its relationship with autochthonous sources. In this study, petrographic analyzes, textural parameters in particle distribution (Laser Difraction), geochemistry (X-Ray Fluorescence with Dispersive Energy) and statistics were used. The studied sediments are essentially composed of garnets, biotite, pyroxene (diopside and augite?), epidote, monazite, hornblende, ilmenite, zircon, rutile, titanite, silimanite, kyanite, and quartz. The investigated sediments are similar to the lithotypes found regionally, thus possibly indicating a strong correlation between source rocks and sedimentary deposits. The redox environment is marked by the presence of Fe oxides, probably hematite. The alteration index supports a moderate degree, where micas are preserved, in whole or in part. Keywords: Unconsolidated Sediments, Beach Deposits; Chemical watering. GEOQUÍMICA Y PETROGRAFÍA DE DEPÓSITOS CUTERNARIOS DE LA PORCIÓN SW DE PRAIA BRAVA, ARMAÇÃO DOS BÚZIOS, RJ, BRASIL: EDFRX Y DIFFRACCIÓN LÁSER Resumen: Este artículo presenta los datos geoquímicos y petrográficos de sedimentos de playa de la región SO de Praia Brava (PB) en Armação dos Búzios-RJ. Buscamos discutir los procesos de meteorización química y procedencia, así como analizar el entorno geoquímico y su relación con fuentes autóctonas. En este estudio se utilizaron análisis petrográficos, parámetros texturales en distribución de partículas, geoquímica y estadística con la ayuda de Difracción Láser y Fluorescencia de Rayos X con Energía Dispersiva. Los sedimentos estudiados están compuestos fundamentalmente por granate, biotita, piroxeno (¿diópsido y augita?), Epidota, monacita, hornblenda, ilmenita, circón, rutilo, titanita, silimanita, cianita, además de cuarzo. Los sedimentos investigados son un reflejo de los litotipos encontrados regionalmente, lo que posiblemente indique una fuerte correlación entre las rocas generadoras y los depósitos sedimentarios. El entorno redox está delimitado por la presencia de óxidos de Fe, probablemente hematita. El índice de cambio calculado admite un grado moderado en el que se conservan las micas, ya sea total o parcialmente. Palabras clave: Sedimentos no consolidados; Depósitos en la playa; Meteorización química.