scholarly journals Interpretation of sedimentological processes of coarse-grained deposits applying a novel combined cluster and discriminant analysis

2017 ◽  
Vol 9 (1) ◽  
Author(s):  
Éva Farics ◽  
Dávid Farics ◽  
József Kovács ◽  
János Haas
Keyword(s):  
Discriminant Analysis ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Quantitative Composition ◽  
Shape Parameters ◽  
Homogeneous Groups ◽  
Geological Processes ◽  
Depositional Processes ◽  
Sampling Locations ◽  
Buda Hills

AbstractThe main aim of this paper is to determine the depositional environments of an Upper-Eocene coarse-grained clastic succession in the Buda Hills, Hungary. First of all, we measured some commonly used parameters of samples (size, amount, roundness and sphericity) in a much more objective overall and faster way than with traditional measurement approaches, using the newly developed Rock Analyst application. For the multivariate data obtained, we applied Combined Cluster and Discriminant Analysis (CCDA) in order to determine homogeneous groups of the sampling locations based on the quantitative composition of the conglomerate as well as the shape parameters (roundness and sphericity). The result is the spatial pattern of these groups, which assists with the interpretation of the depositional processes. According to our concept, those sampling sites which belong to the same homogeneous groups were likely formed under similar geological circumstances and by similar geological processes.In the Buda Hills, we were able to distinguish various sedimentological environments within the area based on the results: fan, intermittent stream or marine.

scholarly journals Sedimentology, petrography, and reservoir quality of the Zarga and Ghazal formations in the Keyi oilfield, Muglad Basin, Sudan

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yousif M. Makeen ◽  
Xuanlong Shan ◽  
Habeeb A. Ayinla ◽  
Ekundayo Joseph Adepehin ◽  
Ndip Edwin Ayuk ◽  
...  
Keyword(s):  
Thin Section ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Reservoir Quality ◽  
Research Attention ◽  
Sequence Composition ◽  
Exploration And Production ◽  
Authigenic Mineral ◽  
Thin Section Analysis

AbstractThe Zarga and Ghazal formations constitute important reservoirs across the Muglad Basin, Sudan. Nevertheless, the sedimentology and diagenesis of these reservoir intervals have hitherto received insignificant research attention. Detailed understanding of sedimentary facies and diagenesis could enhance geological and geophysical data for better exploration and production and minimize risks. In this study, subsurface reservoir cores representing the Zarga formation (1114.70–1118.50 m and 1118.50–1125.30 m), and the Ghazal formation (91,403.30–1406.83 m) were subjected to sedimentological (lithofacies and grain size), petrographic/mineralogic (thin section, XRD, SEM), and petrophysical (porosity and permeability) analyses to describe their reservoir quality, provenance, and depositional environments. Eight (8) different lithofacies, texturally characterized as moderately to well-sorted, and medium to coarse-grained, sub-feldspathic to feldspathic arenite were distinguished in the cored intervals. Mono-crystalline quartz (19.3–26.2%) predominated over polycrystalline quartz (2.6–13.8%), feldspar (6.6–10.3%), and mica (1.4–7.6%) being the most prominent constituent of the reservoir rocks. Provenance plot indicated the sediments were from a transitional continental provenance setting. The overall vertical sequence, composition, and internal sedimentary structures of the lithofacies suggest a fluvial-to-deltaic depositional environment for the Ghazal formation, while the Zarga formation indicated a dominant deltaic setting. Kaolinite occurs mainly as authigenic mineral, while carbonates quantitatively fluctuate with an insignificant amount of quartz overgrowths in most of the analyzed cores. Integration of XRD, SEM, and thin section analysis highlights that kaolinite, chlorite, illite, and smectite are present as authigenic minerals. Pore-destroying diagenetic processes (e.g. precipitation, cementation, and compaction etc.) generally prevailed over pore-enhancing processes (e.g. dissolution). Point-counted datasets indicate a better reservoir quality for the Ghazal formation (ɸ = 27.7% to 30.7%; K = 9.65 mD to 1196.71 mD) than the Zarga formation (17.9% to 24.5%; K = 1051.09 mD to 1090.45 mD).

Multi-scale influence of topography on shallow-marine successions associated with long-term transgressions

2021 ◽  
Author(s):  
Miquel Poyatos-Moré ◽  
Ernesto Schwarz ◽  
Salvador Boya ◽  
Luz Elena Gomis-Cartesio ◽  
Ivar Midtkandal
Keyword(s):  
Regional Scale ◽  
Coarse Grained ◽  
Continuous Exposure ◽  
Entire Study ◽  
Shallow Marine ◽  
Sedimentary Characteristics ◽  
Multi Scale ◽  
Depositional Processes ◽  
Mouth Bars

<p>Thick shallow-marine successions associated with long-term transgressions are less well known than their thin, well-sorted counterparts, widely studied due to their potential to form good reservoirs. In these successions, particularly in storm-dominated examples, bioturbation can obliterate primary sedimentary characteristics, making stacking patterns and sequences difficult to define, and challenging our understanding of the main controls in their resulting depositional architecture. This study presents an example from the Jurassic of the Neuquén Basin (Argentina), with the aim to: a) refine the depositional model of a thick, shallow-marine succession associated with a long-term, early post-rift transgression, b) constrain multi-scale controls on stratigraphic architecture and lateral facies variability, and c) discuss their preservation and response to post-depositional processes. To do this, a <300 m-thick succession has been studied along a >10 km continuous exposure, with mapping, sedimentary logging and correlation of stratigraphic units, integrated with subsurface, biostratigraphic and ichnological data. The succession shows an overall retrogradational-aggradational-retrogradational stacking pattern, with several higher frequency regressive units (parasequences and parasequence sets, PSS). The lower part (PSS I) comprises laterally-discontinuous (10's of m) mouth-bars and distributary channel fills, dominated by several m-thick coarsening- and fining-up sandstone packages and m-scale erosive conglomeratic lenses. Above these, the succession (PSS II-IV) is composed by laterally-continuous (>100's of m) storm-dominated lower-shoreface to upper-offshore deposits, dominated by <1m-thick fine-grained and highly bioturbated tabular muddy sandstones and sandy mudstones, with rarely-preserved HCS and bioclastic-rich limestones; their internal characteristics and bed boundaries are diffuse due to pervasive bioturbation, suggesting overall low sedimentation rates and recurrent periods of colonization. The coarse-grained nature and lithology of the mouth bars and channel fills in the lower succession (PSS I) are consistent with a proximal sediment source, associated with erosion of intra-basinal highs. Its variable thickness, lateral distribution and onlap against underlying syn-rift deposits demonstrates partial infill of localized higher-accommodation areas. The well-sorted and finer-grained nature of the shoreface-offshore strata the middle and upper succession (PSS II-IV) indicates a more mature, distal source, with sediment redistributed by longshore currents, and then intensely bioturbated. These deposits display well-defined parasequences internally composed of laterally-continuous bedsets (<5 m-thick). They extend along the entire study area, but show a significant vertical thickness variability. The integration of outcrop and subsurface data mapping (well and seismic) reveals this variability records the stratigraphic response of transgression over a complex, regional-scale ramp-step and underfilled rift topography, which controlled the location of main thickness and facies changes, and promoted areas of favored biogenic reworking. This study offers new insights in how to interpret thick transgressive successions based on primary depositional mechanisms and postdepositional processes, and provides useful tools to understand and predict the nature and potential preservation of these deposits in limited subsurface datasets.</p>

scholarly journals Evolution of the early Mesozoic Cordilleran arc: The detrital zircon record of back-arc basin deposits, Triassic Buckskin Formation, western Arizona and southeastern California, USA

Geosphere ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 1042-1057
Author(s):  
N.R. Riggs ◽  
T.B. Sanchez ◽  
S.J. Reynolds
Keyword(s):  
North America ◽  
Detrital Zircon ◽  
Colorado Plateau ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Land Bridge ◽  
Magmatic Arc ◽  
Early Mesozoic ◽  
Northern Nevada ◽  
Back Arc

Abstract A shift in the depositional systems and tectonic regime along the western margin of Laurentia marked the end of the Paleozoic Era. The record of this transition and the inception and tectonic development of the Permo-Triassic Cordilleran magmatic arc is preserved in plutonic rocks in southwestern North America, in successions in the distal back-arc region on the Colorado Plateau, and in the more proximal back-arc region in the rocks of the Buckskin Formation of southeastern California and west-central Arizona (southwestern North America). The Buckskin Formation is correlated to the Lower–Middle Triassic Moenkopi and Upper Triassic Chinle Formations of the Colorado Plateau based on stratigraphic facies and position and new detrital zircon data. Calcareous, fine- to medium-grained and locally gypsiferous quartzites (quartz siltstone) of the lower and quartzite members of the Buckskin Formation were deposited in a marginal-marine environment between ca. 250 and 245 Ma, based on detrital zircon U-Pb data analysis, matching a detrital-zircon maximum depositional age of 250 Ma from the Holbrook Member of the Moenkopi Formation. An unconformity that separates the quartzite and phyllite members is inferred to be the Tr-3 unconformity that is documented across the Colorado Plateau, and marks a transition in depositional environments. Rocks of the phyllite and upper members were deposited in wholly continental depositional environments beginning at ca. 220 Ma. Lenticular bodies of pebble to cobble (meta) conglomerate and medium- to coarse-grained phyllite (subfeldspathic or quartz wacke) in the phyllite member indicate deposition in fluvial systems, whereas the fine- to medium-grained beds of quartzite (quartz arenite) in the upper member indicate deposition in fluvial and shallow-lacustrine environments. The lower and phyllite members show very strong age and Th/U overlap with grains derived from Cordilleran arc plutons. A normalized-distribution plot of Triassic ages across southwestern North America shows peak magmatism at ca. 260–250 Ma and 230–210 Ma, with relatively less activity at ca. 240 Ma, when a land bridge between the arc and the continent was established. Ages and facies of the Buckskin Formation provide insight into the tectono-magmatic evolution of early Mesozoic southwestern North America. During deposition of the lower and quartzite members, the Cordilleran arc was offshore and likely dominantly marine. Sedimentation patterns were most strongly influenced by the Sonoma orogeny in northern Nevada and Utah (USA). The Tr-3 unconformity corresponds to both a lull in magmatism and the “shoaling” of the arc. The phyllite and upper members were deposited in a sedimentary system that was still influenced by a strong contribution of detritus from headwaters far to the southeast, but more locally by a developing arc that had a far stronger effect on sedimentation than the initial phases of magmatism during deposition of the basal members.

Plant Taphonomy in Areas of Explosive Volcanism

1986 ◽  
Vol 15 ◽  
pp. 1-9 ◽  
Author(s):  
William J. Fritz
Keyword(s):  
Explosive Volcanism ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Continental Margins ◽  
Fossil Plants ◽  
Common Part ◽  
Geologic Record

Coarse-grained volcaniclastic sediments are a common part of the non-marine geologic record along most continental margins. Many of these volcanic sediment units contain well-preserved assemblages of fossil plants. Because much of the work on depositional environments, dating, correlations and paleoenvironments has been derived from studies of plants, it is important to understand the processes that incorporate the plants into the volcaniclastic sediments. In this paper I plan to concentrate on processes that bury and preserve trees, logs and stumps.

scholarly journals The Permian-Triassic boundary in Wyoming: the case of the disappearing paraconformity

1992 ◽  
Vol 6 ◽  
pp. 242-242
Author(s):  
James M. Renner ◽  
Donald W. Boyd
Keyword(s):  
Depositional Environment ◽  
Depositional Environments ◽  
Compelling Evidence ◽  
Carbonate Facies ◽  
Triassic Boundary ◽  
Physical Evidence ◽  
Depositional Processes ◽  
Marine Facies ◽  
Permian Triassic Boundary ◽  
Continuous Deposition

Long-standing interpretations of paleontologic, sedimentologic, and stratigraphic evidence from Permian-Triassic marine sequences in western Wyoming have suggested an interruption in deposition of several million years' duration between the two systems, even though physical evidence of unconformity is subtle and somewhat equivocal. We postulated that an unconformity of this duration should be more pronounced in paralic and non-marine facies in central and southeast Wyoming than in adjacent inner-shelf marine facies in westcentral Wyoming. Therefore, we correlated an erathem boundary-bearing sequence from westcentral Wyoming (where it is faunally controlled) to southeast Wyoming (where it is non-fossiliferous) and studied this sequence for evidence of hiatus. The correlations were made using surface sections, surface gamma-radiation logs, and subsurface log suites.In southeast Wyoming, the lithostratigraphic equivalent to the systemic boundary in westcentral Wyoming is located within a redbed-evaporite sequence traditionally interpreted as having accumulated in paralic and/or terrestrial depositional environments. Physical evidence of disconformity at this surface in southeast Wyoming is no greater, and is in places less, than at several other horizons within the boundary-bearing sequence. Also, petrologic examination of the terrigenous clastic units below, through, and above the boundary-bearing sequence in central and southeast Wyoming suggests notable stability of the depositional environment. Southeastward stratigraphic thinning of various units within this boundary-bearing sequence is demonstrable; however, compelling evidence of regional truncation is not evident, and the stratigraphic thinning appears to be due to primary depositional processes rather than post-depositional erosion during hiatus.We interpret slow, episodic, yet generally continuous deposition of evaporite and siliciclastic units in southeast Wyoming across the Permian-Triassic boundary. If true, then conventional biostratigraphic estimates of the duration of a hiatus separating Permian inner and middle-shelf carbonate facies from overlying Triassic siliciclastics in western Wyoming appear to be overly long, and may need re-evaluation.

Dating lacustrine carbonate strata with detrital zircon U-Pb geochronology

Geology ◽  
2020 ◽  
Author(s):  
Emily S. Finzel ◽  
Justin A. Rosenblume
Keyword(s):  
Detrital Zircon ◽  
Relative Proportion ◽  
Foreland Basin ◽  
Depositional Environments ◽  
Detrital Zircons ◽  
Sediment Flux ◽  
Coarse Grained ◽  
Southwestern Montana ◽  
Tectonically Active ◽  
Lacustrine Carbonate

Carbonate lacustrine strata in nonmarine systems hold great potential for refining depositional ages through U-Pb dating of detrital zircons. The low clastic sediment flux in carbonate depositional environments may increase the relative proportion of zircons deposited by volcanic air fall, potentially increasing the chances of observing detrital ages near the true depositional age. We present U-Pb geochronology of detrital zircons from lacustrine carbonate strata that provides proof of concept for the effectiveness of both acid-digestion recovery and resolving depositional ages of nonmarine strata. Samples were collected from Early Cretaceous foreland basin fluvial sandstone and lacustrine carbonate in southwestern Montana (USA). Late Aptian–early Albian (ca. 115–110 Ma) maximum depositional ages young upsection and agree with biostratigraphic ages. Lacustrine carbonate is an important component in many types of tectonic basins, and application of detrital zircon U-Pb geochronology holds considerable potential for dating critical chemical and climatic events recorded in their stratigraphy. It could also reveal new information for the persistent question about whether the stratigraphic record is dominated by longer periods of background fine-grained sedimentation versus short-duration coarse-grained events. In tectonically active basins, lacustrine carbonates may be valuable for dating the beginning of tectonic subsidence, especially during periods of finer-grained deposition dominated by mudrocks and carbonates.

Environmental control on granular clinoforms of ancient carbonate shelves

2006 ◽  
Vol 143 (3) ◽  
pp. 343-365 ◽  
Author(s):  
A. QUIQUEREZ ◽  
G. DROMART
Keyword(s):  
Environmental Control ◽  
Depositional Environments ◽  
Angle Of Repose ◽  
Coarse Grained ◽  
Carbonate Platforms ◽  
Carbonate Sediment ◽  
Sediment Grain Size ◽  
Sedimentary Structures ◽  
Lower Slope ◽  
Sediment Fabric

The purpose of this paper is to document the influence of depositional environments on shallow-water, low-relief clinoforms from the description of five ancient carbonate platforms: the Neoproterozoic (Namibia), Middle Jurassic (France), Lower Cretaceous (France), Upper Cretaceous (Oman) and Miocene (Turkey). These examples have been investigated on the basis of field observations. The clinoforms are described with reference to geometric and compositional attributes: declivity, shape, height, sedimentary structures, sediment fabric and components. The results show great variability in stratal geometry, declivity and facies distribution: (1) depositional profiles vary from exponential, to sigmoidal, to oblique; (2) maximal slope angles range from 3 to 25°, most of them being grouped between 10 and 18°; (3) facies differentiation identified from lateral facies successions along beds, and vertical facies successions through beds, is pronounced to subtle. This study documents linkages between depositional environments and clinoform attributes. Proximal/shallow clinoforms display round-edged exponential profiles. Sediment deposition has resulted from unidirectional currents in the upper convex section, and storm-generated oscillatory currents in the lower concave part. The sediment fabric changes gradually along this type of clinoform. There is little vertical facies differentiation through these clinobeds which have formed from a continuous amalgamation of deposits. By contrast, distal clinoforms (shelf break, distally steepened ramp settings) yield a much broader spectrum of profiles and are generally shorter and steeper. Sedimentary structures in gravel-sized deposits of the upper slope indicate pure traction by unidirectional currents. Conversely, marks of oscillatory flows (undular, wavy top bounding surfaces of clinobeds) are common in the lower slope. Intercalation of massive, fine-grained deposits suggests offshore transport of carbonate mud by suspension. Each distal clinobed represents a single flow event. Accordingly, facies differentiation is weak laterally but may be pronounced through the clinobeds. Our study suggests that low-relief forms of proximal/shallow environments, which contain coarse-grained and photo-independently produced debris, record hydrodynamic equilibrium profiles, whereas the higher-relief forms of this setting rather reflect a high differential production rate of carbonate sediment with water depth. The carbonate sediment of the distal clinobeds mainly derives from skeletal production by oligophotic and photo-independent biota of the middle shelf/ramp and upper portion of the clinoforms. The contribution by in situ skeletal biota only becomes significant on the lower slope, indicating that the distal, submerged slopes of carbonate platforms are not organically but hydrodynamically generated. Our compilation shows that the slope angles of shallow marine, low-relief clinoforms do not simply correlate to the sediment grain size and fabric, in contrast to what has been documented for the high, linear slope profiles. This difference stems from the depositional settings, namely the involved transport mechanisms. Low-relief clinoform accretion seems to be dominantly influenced by wave-induced sediment transport, in contrast to linear flanks of high-relief clinoforms that build to the angle of repose, and for which gravity is the primary transport process.

scholarly journals On the Use of Linear Discriminant Functions in the Realm of Industrial Accident Insurance

1962 ◽  
Vol 2 (2) ◽  
pp. 198-207 ◽  
Author(s):  
J. van Klinken
Keyword(s):  
Discriminant Analysis ◽  
Accident Insurance ◽  
Accident Risk ◽  
Industrial Accidents ◽  
Homogeneous Groups ◽  
Linear Discriminant ◽  
Risk Levels ◽  
Industrial Enterprises ◽  
Risk Functions ◽  
General Meaning

Discriminant analysis is an application of multivariate analysis, which may have its use in determining accident risk levels and premiums of industrial enterprises. This paper only aims to give some suggestions. The following questions will be considered.1. Determining a discriminant function which makes it possible to discriminate between the risk levels of the industrial branches in an efficient way. The industrial branches comprise enterprises with comparable risk levels, hence they are to be considered as homogeneous groups. The function will at the same time serve as a means to classify seperate enterprises into one of these groups.2. Fixing risk functions which enable us to rank the enterprises of an industrial branch to increasing risk on the ground of observations of a number of variates which characterize the risk situation.3. Using these risk functions to calculate premiums. The classification-question mentioned under I was the reason to consider the technique of the discriminant analysis. By virtue of the Dutch Industrial Accidents Act every five years a tariffdecree is being published. This decree contains the premiums per wage-unit for the industrial branches. However, there are enterprises e.g. large compound enterprises which do not fall under these regulations. These enterprises ought to be classified according to their own experience. That means we need the knowledge of the risk levels of these particular enterprises in relation to the fixed risk levels of the industrial branches. As mentioned, this is a problem inherent to the typical Dutch situation. It seems, however, probable that such problems and the techniques we intend to sketch have a wider and more general meaning for the accident insurance.

Origins and engineering hazards of Swedish glaciomarine and marine clays

1991 ◽  
Vol 7 (1) ◽  
pp. 257-264 ◽  
Author(s):  
R. L. Stevens ◽  
M. S. Rosenbaum ◽  
L. G. Hellgren
Keyword(s):  
Urban Areas ◽  
Urban Expansion ◽  
Three Dimensional ◽  
Depositional Environments ◽  
Coarse Grained ◽  
Land Uplift ◽  
Fine Grained ◽  
Depositional Settings ◽  
Late Weichselian ◽  
Three Dimensional Models

AbstractThis paper relates the Engineering features of fine-grained clays in the Göteborg area to their glacial sources, depositional settings and postdepositional changes. These deposits occupy valley and coastal areas where urban expansion has been concentrated, despite the considerable problems with settlement and quick-clay behaviour. Both mineralogical and permeability trends are largely determined by the textural characteristics of the deposits. The depositional environments, which have largely controlled the textural trends, are known to have evolved during late Weichselian times due to glacial retreat, isostatic land uplift and climatic changes. A generalized lithostratigraphical model has been produced and this is used here to help understand and predict the variability of the geotechnical properties. The stratigraphical trends in texture, mineralogy and structure are considered within four broad genetic categories: 1) coarse-grained glacial deposits, 2) glaciomarine deposits, 3) very distal glaciomarine deposits, and 4) shallow-marine deposits. These divisions can often be recognized within the logs of geotechnical reports, which suggested that they could provide the basis for development of three-dimensional models which have both geological and geotechnical predictive power within the vicinity of Göteborg. They could also act as a guide for the development of similar models in urban areas elsewhere.

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