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Microfacies of detrital event layers deposited in Quaternary varved lake sediments of the Piànico-Sèllere Basin (northern Italy) (2005)

MANGILI, C. ; BRAUER, A. ; MOSCARIELLO, A. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Sedimentology 52 (2005), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: A Quaternary interglacial lake sediment record from the Piànico-Sèllere Basin (northern Italy) consists of biochemical calcite varves with intercalated detrital layers. At the end of the Piànico Interglacial, continuous varve formation was replaced by predominantly detrital sedimentation. However, 427 varve-years before this shift, an abrupt increase in the frequency and thickness of detrital layers occurred. Microfacies analyses reveal a total of 152 detrital layers, ranging from 0·2 to 20·15 mm in thickness, deposited during the last 896 years of the Piànico Interglacial. Three microfacies types are distinguished: (i) graded layers, (ii) non-graded silt layers, and (iii) matrix-supported layers. The position of detrital layers within an individual varve provides additional information on the season in which they have been deposited. Microfacies analyses in combination with varve counting further enabled precise varve-to-varve correlation of the detrital layers for two sediment sections cropping out ca 130 m apart. The detailed intra-basin correlation allows the source regions of detrital layers to be inferred. Moreover, micro-erosion at sub-millimetre scale has been established. Of the described facies types, only the accumulation of summer and spring graded and non-graded silt layers abruptly increased before the end of interglacial varve formation whereas non-graded winter silt and matrix-supported layers are randomly distributed over the entire study period. Heavy rainfalls are assumed to have triggered spring and summer graded layers, so that the occurrence of these layers is thought to be a proxy for extreme precipitation events in the past.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.2005.00717.x

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The glaciogenic unconformity of the southern North Sea (2012)

Moreau, J. ; Huuse, M. ; Janszen, A. ; [et al.]

In: Geological Society Special Publication 368: 99-110.

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Publication Date: 2012-12-11

Description: The southern North Sea is a shallow epicontinental sea that was glaciated several times during the Quaternary. The area is known for its remarkable record of tunnel valleys, the age and origin of which are debated. The recent availability of continuous three-dimensional seismic data between the coasts of Britain and the Netherlands provides the opportunity to establish a new seismic interpretation workflow adapted to the intracratonic glaciogenic successions. By analysing the geomorphology of the buried basal glaciogenic unconformity, four distinct major ice fronts are identified and correlated onshore. The ice fronts provide robust relative timelines, and the analysis of tunnel-valley orientations and their merging points indicates that the number of glacial phases has been underestimated. By comparing the erosion capacities of sand and chalk substrates, it is suggested that mechanical abrasion processes are also involved during tunnel-valley genesis. The methods and observations used in this study are applicable to the ancient glaciogenic record in general and constitute a basis for the sedimentological analysis of tunnel valleys.

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Tunnel valleys: current knowledge and future perspectives (2012)

van der Vegt, P. ; Janszen, A. ; Moscariello, A.

In: Geological Society Special Publication 368: 75-97.

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Publication Date: 2012-12-11

Description: Tunnel valleys are elongated incisions that are commonly interpreted as being the result of erosional processes by subglacial meltwater occurring under continental ice sheets. The abundance, size and the primarily coarse-grained infill of these features have made tunnel valleys important hydrocarbon and groundwater reservoirs. Although numerous tunnel valleys have been described over the last century, their formation and infill remain poorly understood. This review summarizes and discusses the current knowledge of tunnel valleys, providing an overview of the observations around the world. Morphological aspects that separate tunnel valleys from other landforms are discussed, as well as the wide variety of sedimentary environments found to contribute to the infilling of these features. The depth of the incision and the character of ice retreat significantly determine the final infill architecture. The formational hypotheses proposed in the literature are assessed to test their wider applicability to all other tunnel valleys in order to find a generic model that helps in the prediction of the morphology and infilling of both Pleistocene and pre-Pleistocene age. A quasi-steady-state model, with small meltwater outbursts that erode tunnel valleys near the ice margin, seems compatible with most of the known valleys. Other proposed models require specific geographical or climatic conditions.

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Glaciogenic reservoirs and hydrocarbon systems: an introduction (2012)

Huuse, M. ; Le Heron, D. P. ; Dixon, R. ; [et al.]

In: Geological Society Special Publication 368: 1-28.

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Publication Date: 2012-12-11

Description: Glaciogenic reservoirs host important hydrocarbon and groundwater resources across the globe. Their complexity and importance for exploration and palaeoclimate reconstruction have made glaciogenic successions popular subjects for study. In this paper we provide an overview of the palaeoclimatic and tectonic setting for Earth glaciation and a chronological account of glaciogenic deposits since c. 750 Ma, with particular emphasis on their reservoir potential and associated hydrocarbon systems. Hydrocarbon accumulations within glaciogenic reservoirs occur principally in Palaeozoic (Late Ordovician and Permo-Carboniferous) sandstones in South America, Australia, North Africa and the Middle East, with relatively minor occurrences of shallow gas hosted in Pleistocene deposits in the North Sea and Canada. Groundwater reserves occur within glaciogenic sandstones across the northern European lowland and in North America. The main glaciogenic environments range from subglacial to glacier front to proglacial and deglacial. Rapidly changing environments, hydrodynamic regimes and glacier-front and subglacial deformation often result in very complex glaciogenic sequences with significant challenges for reconstruction of their origin and resource importance, which this volume seeks to address.

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Ordovician glacial paleogeography: Integration of seismic spectral decomposition, well sedimentological data, and glacial modern analogs in the Murzuq Basin, Libya (2019)

Bataller FJ, McDougall N, Moscariello A.

Society of Exploration Geophysicists (SEG)

In: Interpretation

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Publication Date: 2019

Description: 〈span〉〈div〉Abstract〈/div〉Ancient glacial sediments form major hydrocarbon plays in several parts of the world; most notably, North Africa, Latin America, and the Middle East. We have described a methodology for reconstructing broad-scale paleogeographies in just such a depositional system, using an extensive subsurface data set from the uppermost Ordovician glacial sediments of the Murzuq Basin of southwest Libya. Our workflow begins with the analysis of a large, high-quality 3D seismic data set, to understand the frequency content. Subsequently, optimum frequency bands are extracted, after applying spectral decomposition, and then recombined into an R (red) G (green) B (blue) blended cube. This volume is then treated as an image within which paleomorphological features can be distinguished and compared with modern glacial analogs. Mapping at different depths (time slices) of these features is then tied, by integration with core and image-log sedimentology, to specific depositional environments defined within the framework of a facies scheme developed using the well data and published outcrop studies. These depositional environments are extrapolated into areas with little or no well data using the spectral decomposition as a framework, always taking into account the significant difference in vertical resolution between the seismic data set and core-scale descriptions. The result of this methodology is a set of calibrated maps, at three different time depths (two-way time travel), indicating paleogeographic reconstructions of the glacial depositional environments in the study area and the evolution through time (at different depths/time slices 2D + 1) of these glacial settings.〈/span〉

Print ISSN: 2324-8858

Electronic ISSN: 2324-8866

Topics: Geosciences

Published by Society of Exploration Geophysicists (SEG)

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Alluvial fans and fluvial fans at the margins of continental sedimentary basins: geomorphic and sedimentological distinction for geo-energy exploration and development (2017)

Moscariello, A.

Geological Society (of London)

In: Special Publications / Geological Society London

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Publication Date: 2017-09-30

Description: Alluvial fans and fluvial fans are the most common depositional landforms along the margins of continental sedimentary basins. Their occurrence is determined by the area, relief and hydrology of the catchment, which ultimately control the relative ratios of sediment v. flow discharge and runoff regimes. Fundamental morphological and process distinctions exist between these two kinds of deposystem, which are seen as essentially different facies associations and internal architectures for the corresponding deposits. Alluvial fans commonly develop over short radial distances (hundreds of metres to a few kilometres) and are constructed by ephemeral, flash flow events that lead to poor organization of the sedimentary facies and overall architecture of the corresponding deposits. By contrast, fluvial (mega)fans are fed by proper river systems, which aggrade much larger volumes of clastic sediment over distances of up to a few hundred kilometres. Distinct channel belt and overbank domains are developed with a marked heterogeneity in the distribution of sedimentary facies, represented by hierarchically well-organized fluvial deposits. The general properties of alluvial and fluvial fans reflect the different potentials for the corresponding successions to host economically attractive oil and gas resources and the different approaches required in exploration and prediction.

Print ISSN: 0305-8719

Electronic ISSN: 2041-4927

Topics: Geosciences

Published by Geological Society (of London)

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Alluvial fans and fluvial fans at the margins of continental sedimentary basins: geomorphic and sedimentological distinction for geo-energy exploration and development (2017)

Moscariello, A.

Geological Society (of London)

In: Special Publications / Geological Society London

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Publication Date: 2017-04-28

Description: Alluvial fans and fluvial fans are the most common depositional landforms along the margins of continental sedimentary basins. Their occurrence is determined by the area, relief and hydrology of the catchment, which ultimately control the relative ratios of sediment v. flow discharge and runoff regimes. Fundamental morphological and process distinctions exist between these two kinds of deposystem, which are seen as essentially different facies associations and internal architectures for the corresponding deposits. Alluvial fans commonly develop over short radial distances (hundreds of metres to a few kilometres) and are constructed by ephemeral, flash flow events that lead to poor organization of the sedimentary facies and overall architecture of the corresponding deposits. By contrast, fluvial (mega)fans are fed by proper river systems, which aggrade much larger volumes of clastic sediment over distances of up to a few hundred kilometres. Distinct channel belt and overbank domains are developed with a marked heterogeneity in the distribution of sedimentary facies, represented by hierarchically well-organized fluvial deposits. The general properties of alluvial and fluvial fans reflect the different potentials for the corresponding successions to host economically attractive oil and gas resources and the different approaches required in exploration and prediction.

Print ISSN: 0305-8719

Electronic ISSN: 2041-4927

Topics: Geosciences

Published by Geological Society (of London)

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ILLITE-SMECTITE-RICH CLAY PARAGENESES FROM QUATERNARY TUNNEL VALLEY SEDIMENTS OF THE DUTCH SOUTHERN NORTH SEA - MINERAL ORIGIN AND PALEOENVIRONMENT IMPLICATIONS (2017)

Šegvić, B., Benvenuti, A., Moscariello, A.

Clay Minerals Society

In: Clays and Clay Minerals

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Publication Date: 2017-02-01

Description: The Pleistocene sediment infill of elongated glacial incisions of the southern North Sea (SNS) is often referred to as tunnel valleys (TVs). The depositional environment is not yet fully understood and the present study addresses this challenge from the perspective of clay-mineral transformation (illite to illite-smectite) reported from the largest Elsterian TV of the SNS. Material acquired from the K14-12 borehole in the Dutch offshore was analyzed by X-ray diffraction (XRD), electron microscopy, electron microprobe, and laser particle-size analysis. Illite and illite-smectite (I-S) appeared as dominant clays along with minor amounts of kaolinite, kaolinite-smectite, and chlorite. The largest amount of I-S is recognized in the main TV portion, while in pre-glacial and uppermost deposits, I-S is less abundant. The XRD peak fitting and deconvolution suggest that I-S consists of several intermediates – ordered (well crystallized illite + R3 I-S) and disordered (R0 I-S + R0 I-SS). Given the average particle sizes (〉2 μm) and Kübler index values (0.415–0.341°2), illite as well as chlorite and kaolinite were interpreted as detrital. On the basis of the distinctive distribution, grain sizes, and compositional variations of I-S, formation by means of early diagenetic in situ smectitization of illite under a cold climate is proposed. The process operated via a series of mixed-layer intermediates derived from an illite component being converted progressively to low-charged smectite. The reaction is marked by a significant net loss of K and Al with replacement by Si in a tetrahedral coordination. Layer-charge imbalance is accommodated by Fe(III) and Mg entering an octahedral sheet, whereas Ca partly fills the interlayer sites. Smectitization rates were controlled by illite grain sizes. The results of the present study support strongly the existence of an ice-marginal freshwater depositional environment at the glacial maximum in the SNS in which early diagenesis at low temperatures resulted in incomplete conversion of illite to smectite.

Print ISSN: 0009-8604

Electronic ISSN: 1552-8367

Topics: Geosciences

Published by Clay Minerals Society

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