Lithofacies Assemblages Research Articles

Sediment records as archives of the Late Pleistocene–Holocene hydrological change in the alluvial Narmada River basin, western India

The rivers of western India are monsoon dominated and have been so throughout the late Quaternary. Sediment accumulation in these river basins has been controlled by climatic and tectonic changes over a time span from the Late Pleistocene to the recent. The lithofacies assemblages associated with the various sediment archives in the Narmada basin range from the boulders of the alluvial fans to overbank fines on the alluvial plains. Estimates, based on clast size, of stream power and competence, bed shear stress and discharge reveal that hydrological conditions during the Late Pleistocene (∼90 ka) were comparable to the present day. The size of the transported clasts and the thickness of the accumulated sediment indicate the influence of basin subsidence rather than an increase in discharge. Discharge estimates based on sedimentary structures preserved in the alluvial-plain facies suggest that the channel had a persistent flow, with a low width–depth ratio and large meander wavelength. The hydrological changes during the Holocene are more pronounced where the early Holocene is marked by a high-intensity hydrological regime that induced erosion and incision of the earlier sediments. The mid-Holocene stream channel was less sinuous and had a higher width–depth ratio and a higher meander amplitude in comparison with the present-day channel. Palaeo-fluvial reconstructions based on the sediment archives in the alluvial reach of the river basin are important tools in understanding the long-term hydrological changes and the intricate fluvial architecture preserved in the Narmada River basin ensures scope for detailed studies to identify phases of weak and enhanced hydrological regimes.

Stratigraphy, optical dating chronology (IRSL) and depositional model of pre-LGM glacial deposits in the Hope Valley, New Zealand

A 110 m thick succession of glacial valley fill is described from Poplars Gully, central South Island, New Zealand. The section consists of eight lithofacies assemblages that represent different stages of ice occupation in the valley. Basal sediments record an ice retreat phase followed by a glacial re-advance which deposited mass flow diamictons and till. A subsequent ice retreat from the site is indicated by the stratigraphic transition from till to thick glacio-fluvial gravels. This is followed by a probably short-lived glacier re-advance that caused folding and thrusting of proglacial sediments. Final glacial retreat from the valley led to the formation of a large proglacial lake. In total, Poplars Gully holds evidence for two major ice advances, separated by a glacial retreat that resulted in complete ice evacuation from the lower Hope Valley. Infrared stimulated luminescence (IRSL) dating on ice-proximal sediments from Poplars Gully yielded six ages between 181 and 115 ka BP. Our stratigraphic logging and dating results show that the fill sequence was not, as previously thought, deposited in association with ice advances during the Last Glacial Maximum (LGM) nor indeed during the last glacial cycle. LGM glaciers later overran the fill but we find that the older glacial sequences are considerably more voluminous than those deposited during the last glacial cycle. We also show that the mid-Pleistocene glaciers carved a much deeper valley trough than did glaciers during the LGM. Taken together these features are likely to reflect a significant difference in the magnitude of successive Pleistocene glaciations in the valley, with the mid-Pleistocene ice advances having been considerably larger than those of the last glacial cycle. The recognition of the in-situ survival of extensive pre-MIS 5 (Marine Isotope Stage) deposits in valley troughs that were later occupied by LGM glaciers represents a new feature in the Quaternary stratigraphy of the Southern Alps. The results demonstrate that New Zealand's commonly very large soft-sedimentary valley fills provide a valuable, yet largely unexploited, terrestrial sedimentary archive of successive glaciations in the region.

Process regime change on a Silurian siliciclastic shelf: controlling influences on deposition of the Gray Sandstone Formation, Pembrokeshire, UK

AbstractShallow marine deposits comprising the Silurian Gray Sandstone Formation (GSF) exhibit pronounced process regime changes through time. The formation was deposited on the southern shelf of the Lower Palaeozoic Welsh Basin (UK), and conformably overlies the Coralliferous Formation. The basal Lithofacies Assemblage A (of Sheinwoodian age) is dominated by a storm‐dominated process regime, comprising shoreface and offshore shelf facies associations. The overlying Lithofacies Assemblage B records a mixed process regime, with units being deposited under both storm‐ and tide‐influenced conditions. Tidal‐influence prevailed during deposition of the overlying Lithofacies Assemblage C, with proximal to distal facies variations across a significant tide‐influenced river delta being observed. A return to storm‐dominated shoreface conditions is seen in the succeeding Lithofacies Assemblage D. Lithofacies Assemblage E (Homerian age) records the return of a tide‐influenced river delta to the area, prior to the conformable transition into the overlying Old Red Sandstone (ORS) Red Cliff Formation (of Ludlow age). Northward thickening of the formation across southern Pembrokeshire into the Musselwick Fault indicates a tectonic control on sedimentation, the formation infilling accommodation space developed in an intra‐shelf half‐graben. Recurring changes in process regime from storm‐ to tide‐influenced sedimentation may be related to the onset and subsequent cessation of tidal resonance in sub‐basins across the shelf area which itself was probably controlled by episodic tectonism. It is proposed that the Coralliferous and Gray Sandstone formations comprise the newly erected Marloes Group. Copyright © 2009 John Wiley & Sons, Ltd.

The Reservoir Potential of the Upper Eocene Carbonates of the Northern Thrace Basin, Turkey

The limestones of Upper Eocene Soğucak Formation are up to 100 m thick in the North of Thrace basin. The Upper Eocene Soğucak Formation consists mainly of shallow water carbonates, and four principal depositional microfacies have been identified: (1) benthic foraminiferal wackestone-packestone, (2) algal-benthic foraminiferal wackestone-packestone, (3) coralgal boundstone, (4) planktonic foraminiferal wackestone-mudstone. A depositional model has been proposed based on the fossil and lithofacies assemblages, which suggests that the inter-reef supplies Miliolidaes and that the core reef supplies algae, corals to the fore-reef and deep sea environment.

Whole-rock geochemistry and heavy mineral analysis as petroleum exploration tools in the Bowser and Sustut basins, British Columbia, Canada

Abstract Principles of chemostratigraphic characterization and correlation employing whole-rock inorganic chemical data and heavy mineral grain counts are applied to the frontier Bowser and Sustut basins. Methodologies commonly used with well samples in mature petroleum provinces can be applied to field samples, providing a vital and practical link between the earliest frontier investigations and more advanced hydrocarbon exploration. The major stratigraphic divisions of the basins, the Bowser Lake and Sustut groups, have markedly different indications of sedimentary provenance from heavy mineral analysis, and are readily differentiated geochemically. Variations in key elements are related directly to the provenance indications identified by heavy minerals. Lithofacies assemblages within the Bowser Lake Group also display contrasting provenance signatures. Sandstones and conglomerates from marine facies (Ritchie-Alger, Todagin, and Muskaboo Creek assemblages) are differentiated from those of the deltaic and nonmarine units (Eaglenest, Skelhorne, Groundhog-Gunanoot and Jenkins Creek assemblages) by higher Fe2O3 and MgO contents, which may relate to increased glauconite contents in marine units. Sandstones and conglomerates from the deltaic to nonmarine units are separated with less certainty by heavy mineral contents and element concentrations or ratios.

Sedimentary Facies Models on Carbonatite in the Upper Shuaiba Member of Lower Cretaceous in Daleel Field, Oman

ABSTRACT The Upper Shuaiba Member (USH) is the main force pay bed in the Daleel field in northern Oman; 5 layers including A, B, C, D, and E were divided in profile, and layer D and layer E are the main beds. With the development of exploration in the Daleel oil field, studying the sedimentary systems about their inner composition and the collocation in dimension, and setting up the sedimentary models in the USH are becoming more and more necessary and important to meet the further exploration requirement. Based on the data of geology, seism, and paleo-biology, according to the analysis method on carbonatite depositional system, the litho-facies assemblage and sedimentary environment in the USH were studied. Intershoal low-lying sub-facies (where the water depth is 10–50 m) and shallow shoal sub-facies (where the water depth is not more than 10 m) were extinguished in the layer D, and storm deposit was found in layer E1, in which intershoal low-lying sub-facies also developed. The feature of the sedimentary sub-facies and the sedimentary condition were analyzed, and the sedimentary model was set up in the article: the carbonatite intershoal low-lying developed under the background of open land in shallow sea, where storm events usually occurred in the Lower Cretaceous in the area.

Facies architecture and paleohydrology of a synrift succession in the Early Cretaceous Choyr Basin, southeastern Mongolia

The Choyr Basin is one of several Early Cretaceous rift basins in southwestern Mongolia that developed in specific regions between north–south trending fold-and-thrust belts. The eastern margin of the basin is defined by high-angle normal and/or strike-slip faults that trend north-to-south and northeast-to-southwest and by the overall geometry of the basin, which is interpreted to be a half graben. The sedimentary succession of the Choyr Basin documents one of the various types of tectono-sedimentary processes that were active in the rift basins of East Asia during Early Cretaceous time. The sedimentary infill of the Choyr Basin is newly defined as the Khalzan Uul and Khuren Dukh formations based on detailed mapping of lateral and vertical variations in component lithofacies assemblages. These two formations are heterotopic deposits and constitute a third-order fluvio-lacustrine sequence that can be divided into transgressive and highstand systems tracts. The lower part of the transgressive systems tract (TST) is characterized by sandy alluvial-fan and braided-river systems on the hanging wall along the western basin margin, and by a gravelly alluvial-fan system on the footwall along the eastern basin margin. The alluvial-fan and braided-river deposits along the western basin margin are fossiliferous and are interpreted to have developed in association with a perennial fluvial system. In contrast, alluvial-fan deposits along the eastern basin margin do not contain any distinct faunas or floras and are interpreted to have been influenced by a high-discharge ephemeral fluvial system associated with fluctuations in wetting and drying paleohydrologic processes. The lower part of the TST deposit fines upward to siltstone-dominated flood-plain and ephemeral-lake deposits that constitute the upper part of the TST and the lower part of the highstand systems tract (HST). These mudstone deposits eventually reduced the topographic irregularities typical of the early stage of synrift basin development, with an associated decrease in topographic-slope gradients. Finally, a high-sinuosity meandering river system drained to the south during the late highstand stage in response to the northward migration of the depocenter. The upper HST deposits are also fossiliferous and are interpreted to have been influenced by a perennial fluvial system, although the average annual discharge of this system was probably less than 5 percent of that involved in the formation of the lower TST deposits along the western basin margin.

Tectonosedimentary evolution of the Plio-Pleistocene Sant’Arcangelo Basin (Southern Apennines, Italy)

Abstract This paper describes a new tectonosedimentary model for the evolution of the Plio-Quaternary Sant’Arcangelo Basin, located in the Southern Apennines of Italy. To this purpose, we carried out a new field survey of the basin fill, closely integrating stratigraphy, facies analysis, and structural and tectonic analyses. The geological map at 1:50 000 scale of the whole basin is the first result of this work. We present a new stratigraphic framework for the Sant’Arcangelo Basin succession, which has been subdivided into five major stratigraphic groups, classified as synthems, following the recognition of major basin-wide unconformities. The synthems include smaller-scale stratigraphic units, which are classified as depositional sequences or sub-synthems. These sub-units are composed of different lithofacies assemblages recording cyclic activation of fluvial, deltaic, shallow marine and lacustrine environments throughout the evolution of the basin. Integration of facies analysis and tectonic data led to the definition of a series of palaeogeographical sketches, encompassing the Piacenzian and late Pleistocene, which mark the main steps in the evolution of the Sant’Arcangelo Basin. Basin-scale hinterland-verging thrust faults and folds controlled the development of sub-basins and the progressive isolation of the Sant’Arcangelo Basin from the Ionian foredeep. The new model presented here defines the Sant’Arcangelo Basin as a triangular-shaped basin, bounded by oppositely verging thrusts. The hinterland-verging Valsinni thrust anticline limited its eastern margin and exerted a major control on the basin evolution.

The reservoir potential of the Eocene carbonates in the Bolu Basin, West of Turkey

The limestone of Eocene Tokmaklar Formation is approximately 18 km in length, about 5 km in width, and up to 700 m thick in the Bolu Basin. The Eocene Tokmaklar Formation consists mainly of shallow water carbonates and five principal depositional microfacies have been identified: 1) Benthic foraminiferal packstone–grainstone, 2) Oolitic packstone–grainstone 3) Algal–intraclastic packstone–grainstone, 4) Coral–benthic foraminiferal grainstone, 5) Peloidal packstone–grainstone. A depositional model has been proposed based on the fossil and lithofacies assemblages which suggest that tidal flat supplies stromatolites and intraclasts and that lagoon supplies pellets to the reef core and fore reef. The carbonates of the Tokmaklar Formation have been altered by the following diagenetic processes; micritization, dissolution, fracturing and cementation. As a result of these diagenetic processes, reefal limestones of the Tokmaklar Formation have lost most of their primary porosity. Secondary porosity formed through the dissolution of micritic cement skeletal and non-skeletal (oolitic) grains during early meteoric diagenesis. Oolitic packstone–grainstone facies have moldic porosity, but was probably limited in extent due to a lack of diagenetic pathways. Also in most microfacies fractures tend to be completely filled by sparry calcite. Consequently fractures reduce the porosity of the Tokmaklar limestones.

The Neoproterozoic Fiq glaciation and its aftermath, Huqf supergroup of Oman

AbstractThe <1.5‐km thick Fiq Member of the Ghadir Manqil Formation, Huqf Supergroup, Oman, contains a succession of Marinoan‐age glacially and non‐glacially influenced deposits overlain by a transgressive, 13C‐depleted, deep‐water dolostone (Hadash Formation) that deepens up into the marine shales and siltstones of the Masirah Bay Formation. The Fiq Member and Hadash–Masirah Bay Formations are well exposed in the core of the Jebel Akhdar of northern Oman and provide a valuable insight into the processes operating during a Neoproterozoic glacial epoch and its aftermath.The Fiq Member comprises seven stratigraphic units (F1–F7) of proximal and distal glacimarine, non‐glacial sediment gravity flow, and non‐glacial shallow marine facies associations. These units can be correlated over almost the entire Neoproterozoic outcrop belt (ca. 80 km) of the Jebel Akhdar. Four units contain glacimarine rainout diamictites, commonly at the top of cycles beneath strong lithofacies dislocations suggesting flooding. The units are thought to have been generated by combined glacio‐isostatic and glacio‐eustatic forcing caused by changing volumes of terrestrial glacier ice. The lateral persistence and thickness of massive diamictite units increase upwards in the stratigraphy, the youngest (F7) diamictite being abruptly overlain by the Hadash Formation. Correlation of lithofacies associations across the rift basin and palaeocurrents indicate that siliciclastic sediment and glacially entrained debris were derived from both basin margins. Open‐water conditions existed during interglacials, attested to by the presence of wave‐rippled sandstones in the western part of the basin. The Hadash carbonate also exhibits variations between east and west, showing that despite an overall deep‐water depositional setting, rift margin and intrabasinal structure continued to exert a control on facies development during the post‐glacial aftermath. Onlap of basin margins continued through the deposition of the Masirah Bay Formation.The sedimentology and stratigraphy of the Fiq Member and Hadash–Masirah Bay Formations have a number of implications for the Snowball Earth hypothesis. The overall stratigraphic evolution of the Fiq Member suggests a dynamic, temperate/polythermal style of glaciation, perhaps nucleated on uplifted continental or rift margin topography, with marine‐terminating glaciers. Some transgressions coupled to deglaciations within the Fiq glacial epoch were accompanied by minor deposition of carbonate. However, final deglaciation triggered the deposition of a <8‐m thick, deep‐water dolomite contaminated with siliciclastics, with a lithofacies assemblage still reflecting the underlying bathymetric template, followed by relatively deep marine shales and siltstones. The preservation of relatively deep marine Masirah Bay sediments above the Fiq basin margin suggests either tectonic collapse of the rift shoulder or, more likely, rapid eustatic rise accompanying deglaciation.

MESOSCALE HETEROGENEITY OF FLUVIAL‐LACUSTRINE RESERVOIR ANALOGUES: EXAMPLES FROM THE EOCENE GREEN RIVER AND COLTON FORMATIONS, UINTA BASIN, UTAH, USA

The Eocene Uinta Basin of Utah is a dominantly lacustrine basin that affords the opportunity to survey analogue sandstone reservoirs developed within and adjacent to the lacustrine system. From its SW to NE margin, Eocene strata in the Uinta Basin record fluvial, deltaic, profundal lacustrine, and wave‐dominated shallow‐lacustrine environments. Of these depositional systems, analogue sandstone reservoirs are well‐exposed in outcrop in the fluvial‐deltaic and wave‐dominated intervals. Field and petrographic examination of selected fluvial‐lacustrine reservoir analogues are used to document the mesoscale facies architecture and heterogeneity. Complex depositional geometries and heterogeneity exist at a variety of scales, both within single subenvironments and between opposite sides of the basin.Three outcrops in the Uinta Basin were studied. Outcrops One and Two are located in the SW portion of the basin in Nine Mile Canyon, and represent the interface between fluvial rocks of the Colton Formation and dominantly lacustrine strata of the Green River Formation. Outcrop Three is located at Raven Ridge in the NE of the basin, a shallow wave‐dominated lacustrine margin. Photomosaics and multiple vertical measured sections were described for each outcrop, and were utilized to document lithofacies assemblages, bounding surfaces, and sandbody architecture and heterogeneity. Sandstone samples from each outcrop were analyzed petrographically to capture the small‐scale heterogeneity characteristic of the three outcrops.Sedimentary rocks at Outcrops One and Two consist of lenticular, tabular, or undulatory channel, distributary channel, and bar deposits that are partially to entirely compartmentalized, or encased, by mudstone units. These sandstone units, analogous to reservoir intervals in lacustrine basins, show various types of lateral and vertical connectivity which are dependent on the degree of amalgamation and the sand:mud ratio. Within these sandbodies, mud chip lags, large mud clast horizons, discontinuous finer‐grained beds, accretion sets and amalgamation surfaces represent internal heterogeneity which could be expected to affect transmissibility in an actual reservoir. The complex geometry and heterogeneity characteristic of these reservoir analogues confirms the need for detailed reservoir characterization studies on all scales in order to improve production efficiency in such systems.Outcrop Three is dominated by tabular and laterally extensive offshore bar and sandsheet deposits which are separated by thick mudstone units. Large‐scale heterogeneity is minimized within these reservoir analogues, in that sandbodies exhibit excellent lateral continuity and less complex amalgamation. Therefore, documentation of heterogeneity at the bed‐ and petrographic‐scale is necessary to better address production potential in these types of reservoirs.

Fácies e elementos arquiteturais resultantes de mudanças climáticas em um ambiente desértico: Grupo Urucuia (Neocretáceo), Bacia Sanfranciscana

The Urucuia Group (Upper Cretaceous) in the Sao Domingos region, State of Goias, consists of conglomerates, sandstones and siltstones deposited in a desert environment. The studied section is located in the central-east Brazil, west border of the Sanfranciscana Basin. Six architectural elements were characterized according to their lithofacies assemblages, geometry and nature of the lower and upper contacts. These elements are divided in an eolian system (field dune deposits) corresponding to simple dunes (SD) and interdunes (ID); and, in a fluvial-eolian system (sand sheet deposits) including dry sand sheet (DSS), wet sand sheet (WSS), wadis (WD) and flood plain (FP). The lower portion of the section indicates a eolian dry system developed under arid climate. The intercalation of eolian and non-eolian deposits in the upper portion (fluvial-eolian system) suggests a climatic variation with an increase of humidity.

Structural and Sedimentologic Evolution of a Miocene Supradetachment Basin, Silver Peak Range and Adjacent Areas, West-Central Nevada

The Silver Peak region of west-central Nevada provides a unique opportunity to study the history of a supradetachment basin, its deformed basement, and the detachment fault itself. The region experienced Late Cretaceous to Paleogene plutonism and stretching of a Neoproterozoic through Ordovician miogeoclinal section. Upper-crustal thinning above the Mineral Ridge pluton was accommodated by development of gently dipping schistosity in Neoproterozoic strata, and a mosaic of low-angle attenuation faults in overlying Cambrian strata. Middle and Late Miocene detachment faulting accommodated approximately 8-15 km of northwest transport of hanging-wall strata. The Mineral Ridge detachment fault apparently reactivated the basal décollement of the Late Cretaceous to Paleogene attenuation faults. The Esmeralda basin evolved in the hanging wall of the detachmentfault system, and represents subsidence over a significantly broader region than modern extensional basins. The supradetachment basin fill consists of three interfingering lithofacies assemblages: (1) an east-derived, conglomeratic, sedimentaclastic, alluvial-fan assemblage deposited adjacent to the breakaway; (2) mudstone and coal deposited in lacustrine and paludal environments; and (3) a westderived, sandy, volcaniclastic assemblage deposited in braidplain/braiddelta environments. Geometric relations indicate that the detachment fault dipped gently while active, and was the sole fault for a stack of listric-normal growth faults. Late Miocene arc volcanism within the Silver Peak region postdated cessation of detachment faulting. Present physiography is controlled by Pliocene to Holocene normal and strike-slip faulting associated with volumetrically minor basaltic volcanism. This complex history of late Mesozoic and Cenozoic deformation, magmatism and sedimentation in the Silver Peak region may be analogous to other parts of the Basin and Range Province, suggesting broad applicability of the model developed herein.

Origin, genetic interrelationships, and stratigraphy over the continuum of fluvial channel-form bounding surfaces: an illustration from middle Cretaceous strata, southeastern Colorado

Abstract A hierarchy of channel-form bounding surfaces generally partitions fluvial strata, each reflecting river scouring processes at a different scale. Low-order (e.g. channel scours, channel-belt boundaries, etc.) and high-order (i.e. valley-form sequence boundaries) surfaces are discussed extensively in the literature. The intermediate-scale boundaries, however, are largely overlooked. An understanding of the range of processes generating these channel-form surfaces is pivotal for interpreting fluvial architecture and understanding sequence-boundary genesis. This paper examines origin, interrelationships, and significance for the full range of channel-form bounding surfaces (channel-fill to sequence boundary) in middle Cretaceous strata of southeastern Colorado, and assesses the role of such surfaces in sequence and allostratigraphy. Middle Cretaceous strata of the Muddy Sandstone were photographed over the entire length (14 km) of the Huerfano Canyon. Lithofacies were then mapped in detail for all Muddy deposits, and bounding surfaces were identified by architectural-element analysis within Muddy fluvial strata. Two alloformations were established based on recognition of three continuous discontinuities. The Cucharas Canyon Alloformation is floored by one sequence-bounding unconformity that is smooth (surface SB3), and is capped by surface SB4. It is mostly a basal sandstone cliff composed of fluvial lithofacies assemblages, but is characterized commonly by paralic lithofacies assemblages in its upper part. The Huerfano Canyon Alloformation is floored by a locally incised sequence boundary SB4, and is capped by a smooth transgressive surface of erosion. It comprises cliff-forming fluvial lithofacies assemblages. Both alloformations reveal six orders of channel-form bounding surfaces. Each order is bundled by surfaces of the succeedingly higher orders; thus, the surfaces can be considered to fit in a hierarchical or ‘nested’ progression. The surfaces record, in order of ascending rank: nested-channel cuts, channel scours, channel-belt boundaries, nested-valley boundaries, valley-fill boundaries, and sequence-bounding unconformities. Though generated by discrete processes, each of these surfaces is formed as a composite of the lower-order surfaces. These surfaces are thus genetically interrelated into a bounding-surface continuum. This continuum is best constrained by allostratigraphic techniques, with sequence stratigraphy and architectural-element analysis treated as approaches under the auspice of allostratigraphy. Middle-Cretaceous strata reveal a close interrelationship between sequence-boundary morphology and architecture of overlying fluvial deposits. Valley-form sequence boundaries tend to record composite surfaces formed of multiple nested-valley scours. Smooth sequence boundaries tend to reflect composites of multilateral channel-fill elements or valley-fills. These observations promote a set of predictive relationships between sequence boundaries and overlying fluvial sandstone that are here categorized into four sequence architectural styles with valley-form boundaries (simple valley, complex valley, compound valley, and compound-complex valley) and four with smooth boundaries (channel sheet, stacked channel sheet, multivalley, and stacked multivalley). Valley and nested-valley incisional boundaries in middle Cretaceous alloformations most likely result from climatic forcing, and do not necessarily record regional surfaces. Such surfaces are abundant in modern deposits, and should be far more common in ancient strata than previously reported. Because of their potential impact on results, they need to be considered as a factor when estimating ratios of accommodation space versus sediment supply, evaluating regional permeability trends, and assessing up-dip fate of sequence-bounding unconformities.

A arquitetura deposicional da Formação Marizal (Cretáceo Inferior) na Bacia do recôncavo, Bahia

The Early Cretaceous Marizal Formation, which is a product of fluvial and alluvial fan systems, is about 50m thick in The Reconcavo Basin, BA, Brazil. This formation changes gradually from conglomerates into sandstones and mudstones. The presence of good continuous outcrops, was essential to the architectural element analysis. This method was used to subdivide the fluvial deposits into one or more sets of nine basic three dimensional architectural elements. These elements were identified according to their lithofacies assemblage, internai geometry, and the nature of the upper and lower contacts. The study of outcrops in the proximal provided key information to identify regions the SG (sediment gravity flows) and GB (gravei bars and bedforms) elements. In the distai regions, the predominam elements are SB (sandy bedforms), LS (laminated sand sheets), DA (downstream accreted macroforms), and less frequently, CH (channels) and LA (lateral accretion deposits). The FF (floodplain fines) element has been identified in both proximal and distai regions. The distribution of these elements reveals two distinct domains in depositional model of The Marizal Formation. The first domain represents a proximal low sinuosity gravelly rivers associated with sediment gravity flows. The second domain is a result of shallow wide river channel depositional model, with sand bed load and low to intermediate sinuosity. The LS local accumulation are an evidence of flash floods in arid to semi-arid climates during deposition of the sediments.

Tectono-sedimentary evolution of the Gondwanan Satpura Basin of central India: evidence of pre-Trap doming, rifting and pal˦oslope reversal

The Mesozoic Gondwanan Satpura Basin of central India, comprising an approximately 1300 m thick sequence of the Pachmarhi, Denwa and Bagra Formations, was subjected to at least three major tectonic events. These events are manifested by tectonic dislocation, marginal uplifts, basin subsidence and deformation, as well as by stratigraphical disposition, lithofacies assemblage, and palaeoslope and pal˦ocurrent patterns. The first tectonic event is manifested by the onset of Early Triassic Pachmarhi sedimentation, which is marked in the basal part by a sudden increase of conglomeratic, pebbly, gritty to coarsegrained cross-bedded sandstone. This contrasts with the underlying fine elastics of the Late Permian Bijori Formation. The stratigraphical relationship and lithofacies, together with pal˦ocurrent and petrographic data, reflect tectonic uplift in the source area to the southeast of the Satpura Basin during or prior to the deposition of Pachmarhi Formation. The pebbly coarse sandy facies of the Pachmarhi Formation represents a braided river assemblage, overlain by a meandering river facies of the Denwa Formation, with river systems flowing dominantly from southeast to northwest. The progressive change in lithofacies and grain size upward from Pachmarhi to Denwa implies that the source area became peneplained and that the basin stabilised. During the prolonged gap of non-deposition, following the Mid-Triassic break in sedimentation after deposition of the Denwa Formation, a second tectonic event resulted in the widespread faulting and uplift of Permo-Triassic Gondwana sediments and basement rocks, respectively, to the south and north of the Narmada-Son Lineament Zone of Peninsular India. A third tectonic event is manifested by Late Jurassic-Early Cretaceous Bagra conglomerate and sandstone-shale facies in the northern part of the Satpura Basin. This formation, which unconformably overlies the Precambrian, and Permian and Triassic Gondwana formations or abuts against faulted contacts, represents proximal and distal facies of an alluvial fan deposit in a rifted (pull-apart?) basin with uplifted highlands to the north. This tectonism, representing the termination of continental Gondwana sedimentation, preceded the widespread eruption of the Deccan Traps (65 Ma) after the break-up of India from Antarctica. As a consequence, a northward sloping, peninsular craton was tilted southward and small rift basins developed along peripheral parts to the north, west and along the east coast of Peninsular India. To the north of the study area, the doming before the Deccan volcanism and tectonic movement along the Narmada-Son Lineament caused uplift of the Palaeoproterozoic Mahakoshal/Bijawar terrane. This uplift was accompanied by a reversal of palaeoslope. Consequently, north to south pal˦currents followed the deposition of the Pachmarhi and Denwa Formations, as borne out by the alluvial fan-braided complex of the Bagra Formation.

Ichnocoenoses of the Mount Messenger Formation, a Miocene submarine fan system, Taranaki Basin, New Zealand

The late Miocene Mount Messenger Formation along the North Taranaki coast comprises a fining‐upwards succession of interbedded sandstones and mudstones previously interpreted as deposits of a series of submarine fans in bathyal to upper bathyal waters. The sequence was divided into three lithofacies associations: thick‐bedded basin floor fan (BFFTK); thin‐bedded basin floor fan (BFFTN); and proximal to distal channel levee complex (CLC). This study recognises a fourth unit, the thick‐bedded Ophiomorpha sandstone lithofacies association (TBOS), as another depositional environment. Ichnology is an important tool in distinguishing the lithofacies assemblages and interpreting original depositional conditions. Each of the lithofacies associations shows a distinctive relationship between lithologic parameters and ichnofauna and ichnofabric. Four ichnocoenoses are recognised, corresponding well with the four lithofacies assemblages. Ichnocoenose I, dominated by fodinichnia, coincides with BFFTK and falls into the Cruziana ichnofacies. Ichnocoenose II, dominated by fodinichnia, coincides with BFFTN and falls into the Zoophycos ichnofacies. Ichnocoenose HI, dominated by fugichnia, coincides with CLC and falls into the Cruziana ichnofacies. Ichnocoenose IV, dominated by domichnia, coincides with TBOS and falls into the Skolithos ichnofacies. Although ichnocoenoses I and III are classed as Cruziana ichnofacies, they are discrete in trace fossil diversity, density, and ethology. Ichnocoenose IV has a unique, monospecific Ophiomorpha assemblage; together with the well‐sorted sand texture, absence of mud, and thick massive bedding, the TBOS lithofacies appears to reflect a different environmental setting to the Mount Messenger Formation with which it is associated.

Stratigraphic response to saline lake-level fluctuations and the origin of cyclic nonmarine evaporite deposits: The Pleistocene Blanca Lila Formation, northwest Argentina

Research Article| February 01, 1997 Stratigraphic response to saline lake-level fluctuations and the origin of cyclic nonmarine evaporite deposits: The Pleistocene Blanca Lila Formation, northwest Argentina Dirk S. Vandervoort Dirk S. Vandervoort 1Institute for the Study of the Continents and Department of Geological Sciences, Cornell University, Ithaca, New York 14853 Search for other works by this author on: GSW Google Scholar Author and Article Information Dirk S. Vandervoort 1Institute for the Study of the Continents and Department of Geological Sciences, Cornell University, Ithaca, New York 14853 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1997) 109 (2): 210–224. https://doi.org/10.1130/0016-7606(1997)109<0210:SRTSLL>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Dirk S. Vandervoort; Stratigraphic response to saline lake-level fluctuations and the origin of cyclic nonmarine evaporite deposits: The Pleistocene Blanca Lila Formation, northwest Argentina. GSA Bulletin 1997;; 109 (2): 210–224. doi: https://doi.org/10.1130/0016-7606(1997)109<0210:SRTSLL>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Stratigraphic analysis of Pleistocene nonmarine bedded evaporites in northwest Argentina elucidates the effect that episodic saline lake expansion and contraction have on the stratigraphic completeness of units deposited and preserved in a continental saline environment. Stratigraphic successions in these rocks contain features that relate uniquely to fluctuations in saline lake level. Bounding the top of each succession is a surface with evidence for an abrupt increase in water depth. Because sediment accumulation and stratal preservation vary spatially as a function of lake level, the degree of stratigraphic completeness varies among locations. These results have implications for attempts to extract the record of continental climate change from saline lake strata.Bedded evaporites in these strata accumulated in a saline lake characterized by a marginal zone of gypsum and ulexite with clastic interbeds and an accumulation of halite in the saline lake center. Four internally conformable successions of genetically related lithofacies assemblages are recognized. Each succession consists of a basal sandstone that is the initial accumulation of the lake-level rise and lake highstand. Overlying this sandstone are cyclic evaporite and fine-grained clastic deposits of the lake-level fall. These units are modified by desiccation-related processes resulting from lake contraction and desiccation around the lake margins. Subsequent lake-level rise resulted in subaqueous mechanical erosion of clastics and dissolution of interbedded evaporites. In more basinward regions, dissolution of evaporites occurred prior to accumulation of lake highstand units. In the saline lake center, the lake never dried up entirely, and evidence for partial lake desiccation is equivocal. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sequential Stratigraphy of Outcropping Strata Equivalent to Arab-D Reservoir, Wadi Nisah, Saudi Arabia

ABSTRACT Two outcrops in Wadi Nisah of Central Saudi Arabia expose sedimentary successions of the Jubaila and Arab formations which are stratigraphic equivalents of the Arab-D reservoir in Ghawar field. These carbonate exposures consist of lithofacies and stacking patterns similar to the succession found in Arab-D reservoir. Nineteen vertical sedimentary cycles were identified by collectively evaluating disconformable relationships, textural characteristics, and lithofacies assemblages. These, in turn, define 3 depositional cycle types: (1) stromatoporoid, (2) skeletal bank, and (3) thinning-upward. The lateral distribution of lithofacies within the stromatoporoid cycle shows that stromatoporoid grainstones form organic buildups flanked by burrowed mud-dominated carbonates. Stromatoporoid banks locally exhibit thickness increases of about 3 meters (10 feet) over a horizontal distance of 500 meters (1, 700 feet). Conversely, the five foot-thick skeletal grainstone capping the skeletal bank cycle forms a continuous sheet exceeding 2 kilometers (1.2 miles) in width. Thinly bedded carbonate sand units within the thinning-upward cycle exhibit pronounced lateral discontinuity. Beds pinch out against topographic highs formed by stromatoporoid buildups over distances of less than a hundred meters (328 feet). Results of the outcrop stratigraphic analysis enable visualization of lateral and vertical stratigraphic relationships and potential fluid-flow pathways. This study demonstrates that outcropping cycles and their lithofacies components have several important implications for ongoing subsurface reservoir characterization and modeling of the Arab-D. Firstly, cycle definition identifies stratigraphic units whose bounding surfaces describe envelopes that constrain the interwell distribution of lithofacies. Secondly, the lithofacies define geometries for the interwell distribution of petrophysical characteristics. Thirdly, the understanding of lateral relationships of these carbonates aids in reservoir simulation modeling.

Bio-lithofacies and diagenesis in the early-middle oligocene of Abu Dhabi, United Arab Emirates

The Early to Middle Oligocene is missing throughout much of the Arabian Peninsula. Only in the Oman Mountains and related linear NW-SE trending mountains are these sediments found. In the United Arab Emirates shallow water carbonates of the Asmari Formation (Early to Middle Oligocene) range from 435–481 m (1427–1578 ft), cropping out at the Jabal Hafit area near Al Ain. Detailed measured sections, sampling and thin section analysis show these carbonates comprise seven distinct facies: 1) Nummulitic Packstone, 2) Foraminiferal Wackestone/Packstone (non-Nummulitic forams), 3) Echinoderm/Red Algal Packstone, 4) Coral Framestone, 5) Peloidal Packstone, 6) Mudstone/Wackestone, and 7) Dolomite. Diagenetic events which have affected the Oligocene section include early cementation, formation of micrite envelopes, inversion of original aragonite and high Mg-calcite fabrics (i.e., biogenic tests and early marine cements) to low Mg-calcite, leaching of tests, dolomitization, stylolitization and fracturing, late diagenetic coarse calcite spar cementation, emplacement of bitumen within stylolitic seams and finally, hematite and pyrite staining. A depositional model has been proposed based on the fossil and lithofacies assemblages which suggests that a deep, outer shelf, quiet water lagoon supplies peloids to the back-reef, reef and fore-reef facies as well as the shallow open marine facies of the inner shelf. A short-lived sea level low is believed to have occurred, where continental waters manifested their presence in rare chertification and partial to complete dolomitization of some samples.