Heterolithic Sediments Research Articles

Facies model of a mixed clastic–carbonate, wave‐dominated open‐coast tidal flat (Tithonian–Berriasian, north‐east Spain)

AbstractDetailed logging and analysis of the facies architecture of the upper Tithonian to middle Berriasian Aguilar del Alfambra Formation (Galve sub‐basin, north‐east Spain) have made it possible to characterize a wide variety of clastic, mixed clastic–carbonate and carbonate facies, which were deposited in coastal mudflats to shallow subtidal areas of an open‐coast tidal flat. The sedimentary model proposed improves what is known about mixed coastal systems, both concerning facies and sedimentary processes. This sedimentary system was located in an embayed, non‐protected area of a wide C‐shaped coast that was seasonally dominated by wave storms. Clastic and mixed clastic–carbonate muds accumulated in poorly drained to well‐drained, marine‐influenced coastal mudflat areas, with local fluvial sandstones (tide‐influenced fluvial channels and sheet‐flood deposits) and conglomerate tsunami deposits. Carbonate‐dominated tidal flat areas were the loci of deposition of fenestral‐laminated carbonate muds and grainy (peloidal) sediments with hummocky cross‐stratification. Laterally, the tidal flat was clastic‐dominated and characterized by heterolithic sediments with hummocky cross‐stratification and local tidal sandy bars. Peloidal and heterolithic sediments with hummocky cross‐stratification are the key facies for interpreting the wave (storm) dominance in the tidal flat. Subsidence and high rates of sedimentation controlled the rapid burial of the storm features and thus preserved them from reworking by fair‐weather waves and tides.

Pre- and Post-consolidated Sediment Deformations in the Transitional Terrigeneous Series PZt (Zechstein/Lower Buntsandstein)in the Grodziec Syncline, Sudetes: Process Interpretation and Regional Implications

In the Grodziec Syncline (Eastern part of the North-Sudetic Synclinorium) the uppermost Zechstein sediments are represented by mudstones and very fine grained sandstones, which smoothly continue into typical Buntsandstein deposits. These sediments belong to Transitional Terrigeneous Series (PZt), which uppermost part is developed as heterolithic tempestites. A zone abundant in pre- and post-consolidated sediment deformation structures was distinguished within heterolithic sediments. The pre-consolidated sediment deformation structures have numerous features of seismites, on the other hand post-consolidated deformation structures raise more doubts about their origin and require more future research. A zone of pre- and post-consolidated sediment deformation is an important correlation horizon for the Grodziec Syncline. Furthermore, such zone is also observed in the analogous deposits of the Fore-Sudetic Monocline in the Glogow–Rudna area.

Depositional facies and ichnology of a tidally influenced coastal plain deposit: the Ogwashi Formation, Niger Delta Basin

The Ogwashi Formation is re-interpreted as tidally influenced coastal plain deposit based on the detailed outcrop description of exposures and facies analysis. Facies associations comprise strata interpreted to be the deposits of the following environments: fluvio-estuarine channels, tidal channels, tidal flats, coastal plain channels and coastal floodplain/mire. The fluvio-estuarine channels deposits are characterised by high-energy conglomerate and coarse-grained sandstone that are strongly to weakly bioturbated with trace fossils belonging to the Skolithos and the depauperate Cruziana ichnofacies. The tidal channel deposit contains mud chips and mud lenses (at the base) and includes mud draped planar and trough cross-beds. The tidal flat deposit comprises sandy heterolithic sediments that are intensely burrowed. The coastal plain channel deposits are mud-filled channels, with sand sheets interpreted as splay deposits and variegated sandy claystone which has undergone pedogenic alteration. The floodplain and mire deposits are light grey mudstone and dark grey carbonaceous mudstone with plant remains and lignite. These depositional successions show a change from marine to non-marine conditions, interpreted to be a result of relative sea level changes. The architectural elements of the coastal plain succession are grouped into channelised, sandy cross-stratified and floodplain deposits. The channelised elements occur either as isolated or as multistorey channel deposits. Sequence stratigraphic interpretation reveals one depositional sequence with a sequence boundary and an erosive transgressive surface of erosion identified by the occurrence of the Glossifungites ichnofacies with sharp, erosive contacts.

Unusual occurrence and stratigraphic significance of the Glossifungites ichnofacies in a submarine paleo-canyon — Example from a Pliocene shelf-edge delta, Southeast Trinidad

Sedimentary rocks belonging to the upper-slope shelf-margin delta of the Paleo-Orinoco River are present at the southeast coastline of Trinidad in the Columbus Basin. The Pliocene Mayaro Formation, exposed as foreshore cliffs, represents the wave-influenced delta front and mouth bar of this system. These deposits consist of thick to very thick hummocky cross-stratified sandstone beds and thin-bedded to laminated heterolithic sediments. They also contain abundant soft-sediment deformation structures and sparse well-preserved softground burrows (e.g. Ophiomorpha nodosa). Towards the north-central part of the outcrop, the delta front deposits are cut across by a paleo-canyon filled with younger mud-dominated prodeltaic sediments. The rare exposure of the canyon-wall exhibits an unusual occurrence of Glossifungites ichnofacies. Contrastingly distinct from archetypal examples, this monospecific suite contains a low abundance of firmground Thalassinoides filled with mud rather than sand. The tracemakers burrowed into a firm medium-grained sandy substrate of the delta front, and the burrows were subsequently passively filled by the mud from the overlying prodeltaic sediments filling the canyon. The deep-tier firmground Thalassinoides suite crosscuts the pre-existing softground trace fossils. Integration of ichnologic, sedimentologic and sequence-stratigraphic datasets indicates that the older delta front sediments are separated from the prodeltaic deposits by distinct episodes of fluctuating relative sea-level controlled by the basin-bounding growth-fault activities and the development of the canyon. Whereas the entire shelf-margin megasequence might have been deposited through a regional scale sea-level lowstand, the local fluctuations in accommodation space resulting from the growth-fault movements and the incision of the canyon were responsible for the shifting positions of the depositional architectural elements of the shelf-edge delta.

Architecture of coastal and alluvial deposits in an extensional basin: the Carboniferous Joggins Formation of eastern Canada

Abstract The Joggins Formation was deposited in the Cumberland Basin, which experienced rapid mid‐Carboniferous subsidence on bounding faults. A 600 m measured section of coastal and alluvial plain strata comprises cycles tens to hundreds of metres thick. The cycles commence with coal and fossiliferous limestone/siltstone intervals, interpreted as widespread flooding events. These intervals are overlain by coarsening‐upward successions capped by planar‐based sandstone mounds, up to 100 m in width that represent the progradation of small, river‐generated delta lobes into a standing body of open water developed during transgression. The overlying strata contain sand‐rich heterolithic packages, 1–8 m thick, that are associated with channel bodies 2–3 m thick and 10–50 m wide. Drifted plant debris, Calamites groves and erect lycopsid trees are preserved within these predominantly green‐grey heterolithic sediments, which were deposited on a coastal wetland or deltaic plain traversed by channel systems. The cycles conclude with red siltstones, containing calcareous nodules, that are interbedded with thin sandstones and associated with both single‐storey channel bodies (1–1·5 m thick and 2–3 m wide) and larger, multistorey channels (3–6 m thick) with incised margins. Numerous channel bodies at the same level suggest that multiple‐channel, anastomosed river systems were developed on a well‐drained floodplain. Many minor flooding surfaces divide the strata into parasequences with dominantly progradational and aggradational stacking patterns. Multistorey channel bodies are relatively thin, fine grained and modestly incised, and palaeosols are immature and cumulative. The abundance and prominence of flooding surfaces suggests that base‐level rise was enhanced, whereas the lack of evidence for abrupt basinward stepping of facies belts, coupled with the absence of strong fluvial incision and mature palaeosols, suggests that base‐level fall was suppressed. These architectural features are considered to reflect a tectonic architectural signature, in accordance with the high‐subsidence basinal setting. Evidence for restricted marine influence and variation in floral assemblages suggests modulation by eustatic and climatic effects, although their relative importance is uncertain.

Sedimentology of magmatically and structurally controlled outburst valleys along rifted volcanic margins: examples from the Nuussuaq Basin, West Greenland

ABSTRACT After a period of early Palaeocene faulting and uplift of the Nuussuaq Basin, West Greenland, two valley systems were incised into the underlying sediments. Incision of the older Tupaasat valley took place during a single drainage event of large water masses, which resulted in catastrophic deposition. The valley was cut along early Palaeocene NW‐ to SE‐trending normal faults, clearly showing that the trend and the relief of the valley were structurally controlled. The valley fill is up to 120 m thick and consists of a lower part of sandstones and conglomerates deposited from catastrophic flows characterized by very high concentrations of suspended coarse‐grained sediment load. Catastrophic deposition was followed by rapid decrease in flow discharge and the establishment of a lacustrine environment within the valley characterized by the deposition of heterolithic sediments. The younger Paatuutkløften valley system was mainly cut into the Tupaasat valley fill, which was completely or nearly completely eroded away in many places. The younger valley is 1–2 km wide and up to 190 m deep. Incision of the Paatuutkløften valley probably reflected renewed tectonic activity and uplift of the basin. This phase was shortly followed by rapid major subsidence. The valley‐fill deposits comprise a uniform succession of fluvial and estuarine sandstones. The valley fill is topped by shoreface sandstones, which are succeeded abruptly by offshore mudstones deposited shortly before and during the initial extrusion of a thick hyaloclastite succession. The Paatuutkløften valley fill is attributed to a very rapid rise in relative sea level contemporary with extensive volcanism. It is suggested that this sequence of events coincided with the arrival of the North Atlantic mantle plume. In several respects, the early Palaeocene valley‐fill deposits of the Nuussuaq Basin are different from idealized facies models for incised valley systems and represent very special cases of incised valleys. Major differences from published examples include the dominance of catastrophic deposits and indications of large changes in relative sea level of several hundreds of metres taking place rapidly in less than 1 Myr. These changes were governed by the rise of the North Atlantic mantle plume.

Sedimentary and structural evidence of a new early Campanian rift phase in the Nuussuaq Basin, West Greenland

A new early Campanian rift phase related to the opening of the Labrador Sea has been recognised in the Nuussuaq Basin, West Greenland. A major angular and erosional unconformity separates deltaic deposits of the upper Albian-lowermost Campanian Atane Formation from fully marine gravity flow deposits of the lower-middle Campanian Aaffarsuaq member of the Itilli formation. Dating of this unconformity was achieved by new field work in the classic Agatdalen area and neighbouring valleys which placed known ammonite localities in an overall stratigraphic scheme and integrated the ammonite dating with a re-evaluation of old and recently collected palynological samples. On the basis of a sedimentological analysis the sediments of the Atane Formation can be classified as pre-rift with respect to Campanian rifting, and the Aaffarsuaq member can be divided into a rift-initiation and main-rift succession. The pre-rift sediments of the Atane Formation are deltaic. The uppermost preserved Atane cycle is 84m thick and is by far the thickest cycle recognised in this formation, suggesting a relative sea-level rise in late Santonian time that was possibly a result of tensional sagging preceding the rift phase. The rift-initiation phase is marked by the major, in places angular, unconformity, locally succeeded by fluvial deposits of the Itivnera beds. During the time of maximum rate of fault displacement sedimentation was outpaced by subsidence, creating relief in the basin. Sedimentation during the main-rift phase was chaotic. Deposition took place mainly from gravity flows in a channelized footwall fan system. During tectonically quiet periods heterolithic sediments were dominantly deposited from low-density turbidity currents in small shallow channels, whereas sandstones and conglomerates were deposited from high-density turbidity currents and debris flows in major channels following tectonically more active periods. Angular unconformities and major erosional surfaces are frequently present underneath the major coarse-grained turbidite channels and several syn-depositional faults are present in the succession, suggesting that these channels formed in response to continued structural movements in the early Campanian.

Sedimentology and depositional setting of the Dartmouth Group, Bigbury Bay, south Devon

The Lower Devonian Dartmouth Group records some of the earliest stages in the evolution of the Variscan basins of southwest England. This thick, mudstone-dominated group has previously been interpreted as distal fluvial sediments, deposited on a coastal mudplain. The sequence at Bigbury Bay is made up of two large-scale sedimentary cycles. The base of each cycle consists of pebbly mudstones, graded siltstones and sandstones, massive mudstones, and heterolithic sediments with sporadic phosphatic nodules. These facies were deposited in substantial lakes; they were modified by phases of syn-sedimentary deformation which generated subaqueous debris flows and turbidites. The overlying parts of the cycle, making up the bulk of the succession, consist of mudstone and thin, sheet-like, sandstones. These are fluvial and were probably deposited in mud-dominated terminal fans. Each cycle represents a phase of rapid, probably fault-controlled, subsidence followed by relative tectonic quiescence. This behaviour may reflect pulses of rifting or extension in strike-slip basins, followed by thermal relaxation.

The Geological Modeling of Effective Permeabilities in Complex Heterolithic Lithofacies

Heterolithic is a term that can be used to describe the complex suite of ripple-scale sedimentary features ranging from flaser-bedded sandstone to sand-streaked mudstone. These facies can contain significant hydrocarbon saturations (e.g., the Kuparuk River Formation, Alaska), but because heterolithic facies form such complex units, the calculation of effective permeabilities and reservoir behavior is difficult. This paper presents a geologically based procedure for calculating effective permeabilities for such facies. Heterolithic sediments can be classified into a limited number of lithofacies types in which flow is controlled by ripple scale sand unit bottlenecks. Clearly, it is important to quantify these features if larger scale flow characteristics are to be evaluated. This is achieved through the use of digitized photographic lithofacies maps and minipermeametry. Effective permeabilities at a number of scales are then calculated for each lithofacies type from the digitized maps using the renormalization procedure. These effective permeability datasets are then used to define the Representative Elementary Volume (REV) for each lithofacies type. REVs are scale-specific effective permeability values for each lithofacies type that fully honor the smaller scale geology. The spatial distribution of these REVs is then modeled from large scale photomosaics and the resultant data input into a blackmore » oil simulator for reservoir behavior studies.« less

Estuarine Trace Fossil Assemblages in Tournaisian Clashmelcon Formation, Kerry Head, Southwest Ireland: ABSTRACT

The Tournaisian Clashmelcon Formation comprises lateral-accretion deposits which fine upward from large-scale cross-stratified sandstone to current-dominated heterolithic beds interbedded with current- and wave-dominated heterolithic beds and desiccated cryptalgal laminites. Large-scale cross-stratification occurs in bundles with structures indicative of unsteady and reversing currents. Wave-dominated heterolithic beds and hummocky cross-stratified sandstone become more abundant upsection. A transported brachiopod-crinoid-bryozoan assemblage which is locally abundant above erosion surfaces becomes more diverse upsection. The Clashmelcon Formation is interpreted as deposits of laterally migrating and aggrading estuarine channels associated with tidal flats which gave way to estuarine embayments dominated by waves. Trace fossils are best developed in heterolithic bedding and include vertical and horizontal burrows. Low in the Clashmelcon Formation, tops of lateral-accretion deposits are locally very bioturbated by a few types of trace fossils including Skolithos, Arenicolites, Teichichnus, Cylindrichnus and, rarely, Glossifungites. Upsection, a more diverse trace fossil assemblage occurs. Wave-dominated heterolithic sediments display a moderately diverse trace fossil assemblage including Teichichnus, Monocraterion, Diplocraterion, Fucusopsis, Planolites, Paleophycus, Chondrites, Neonereites and, rarely, Curvolithus, Rhizocorallium, Bifungites, and Treptichnus. Rhizocorallium is also locally abundant immediately below the basal erosion surfaces of lateral-accretion deposits. Arenicolites, Teichichnus, Fucusopsis, Planolites, Paleophycus, and Chondrites are found in variable abundance throughout much ofmore » the succession. Chondrites is locally very abundant in wave-dominated heterolithic beds and the lower parts of channel fills.« less