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Ichnology of a subaqueously prograding clastic wedge, late Pliocene Morne L'Enfer Formation, Fullarton, Trinidad: Implications for recognition of autogenic erosional surfaces and delineation of stress factors on irregular echinoids

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Abstract

The Morne L'Enfer Formation outcrops near Fullarton, Trinidad, expose an erosional surface between the shelf deposits below and a prograding clastic wedge of the late Pliocene paleo-Orinoco system above. The surface exhibits similarities as well as dissimilarities with examples of Regressive Surfaces of Marine Erosion (RSMEs) in wave-influenced shelf settings and also with incised valleys inherited from fluvial incision of shelf during a forced regression episode. However, detailed ichnological studies reveal that the surface is a subaqueous, autogenically controlled, erosional surface on a shelf dominated by the hyperpycnal and hypopycnal discharges with transient wave influence. Integration of ichnological and sedimentological characteristics also suggests complicated interrelationships among different stress factors affecting the infauna in different subenvironments, especially the irregular echinoids. The delta prograded subaqueously through autogenically establishing its lobe on the open shelf without stratigraphically significant erosional removal of sediments. In the subaqueously prograding clastic wedge, the fluvial influence pertains high stress conditions not only for the adult infauna, but also for their larvae within the water column, especially in and near the subaqueous distributary channels.

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... Additionally, bioturbation was generalised as being indicative of either brackish or marine palaeoenvironments. Dasgupta et al. (2016) examined the sedimentological and ichnological characteristics of the Lower Morne L'Enfer Formation exposed at Fullarton, southwest of Cedros Bay, and described the deposits as belonging to a "wave-influenced and fluvial discharge dominated delta system", bioturbated by elements of the Cruziana ichnofacies. ...
... The purple box demarcates the study area. Modified after: Rohr (1991); Bowman and Johnson (2014); Dasgupta et al. (2016). ...
... The physical evidence described in FA3 clearly indicates, however, that the occurrence of soft sediment deformation cannot be ignored (cf. Dasgupta et al., 2016). ...
... The Lower Morne L'Enfer Formation is considered to be the third wedge, and the Upper Morne L'Enfer Formation makes up the fourth (Chen et al., 2014). The Moruga Formation is subdivided into: (from oldest to youngest) the Gros Morne Silt, the Gros Morne Sandstone, the St. Hilaire Silt, the Trinity Hill Sandstone, the Las Tablas Silt, and the Table 1 Late Miocene to Pleistocene clastic wedges and lithostratigraphic units of the Southern Basin, onshore Trinidad and the dominant depositional processes (Ali et al., 2020;Chen et al., 2018;Dasgupta et al., 2016b;McLean andWilson, 2016 andOsman et al., 2020). ...
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... Highly compressed specimens of Thalassinoides in sandy hyperpycnites may suggest emplacement in water-saturated sand . Exhumation of firm substrates may result from hyperpycnal flow channel erosion, but the lack of available colonisation windows typically prevent burrowing before channel infill (Dasgupta et al., 2016b). However, crustacean burrows penetrate from a colonisation surface at the top of an event bed in the Hatch Mesa succession, reaching the underlying firmground mudstone ( Fig. 11A to C). ...
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The Tonganoxie Sandstone Member (Stranger Formation) records part of the infill of an estuarine valley system that was incised during a late Missourian (Late Carboniferous) drop in sea level and subsequently infilled during a transgressive episode later in the Virgilian (Late Carboniferous). At Buildex Quarry, in an eastern valley margin position, this unit is represented by planar-bedded-andlaminated siltstone beds (tidal rhythmites) overlying a coplanar surface of lowstand erosion and subsequent transgression. These tidal rhythmites contain a relatively diverse ichnofauna dominated by arthropod trackways, surface grazing trails, fish traces, and tetrapod tracks, including the ichnogenera Circulichnis Vyalov, Dendroidichnites Demathieu, Gand, and Toutin-Morin, Diplichnites Dawson, Diplopodichnus Brady, Gordia Emmons, Helminthoidichnites Fitch, Helminthopsis Heer, Kouphichnium Nopcsa, Mirandaichnium Aceñolaza, Stiaria Smith, Stiallia Smith, Tonganoxichnus Mángano, Buatois, Maples, and Lanier, Treptichnus Miller, and Undichna Anderson. The Buildex ichnofauna represents a mixture of the nonmarine Scoyenia and Mermia ichnofacies and records the activity of a terrestrial and freshwater biota. Ichnologic evidence, coupled with sedimentologic data, suggests that the Buildex succession was deposited on tidal flats in the most proximal zone of the inner estuary, between the landward limit of tidal currents and the salinity limit further towards the sea. This type of trace-fossil assemblage seems to characterize the lower part of transgressive system tracts, immediately overlying the coplanar surface during the late Paleozoic. As transgression proceeded, tide-influenced freshwater facies tended to be replaced by retrogradational brackish-water parasequences, and the mixed Scoyenia and Mermia ichnofacies was replaced by a Skolithos-impoverished Cruziana ichnofacies. The coplanar surface (flooding surface and sequence boundary) that marks the base of the Tonganoxie sequence at Buildex lacks the substrate-controlled, marine Glossifungites ichnofacies. The coals and paleosols with upright plant remains that typify the coplanar surface at Buildex represent erosional truncation and subsequent omission close to the interfluves and may be regarded as the landward equivalent of the Glossifungites ichnofacies. Buildex-type ichnofaunas probably are widespread in Pennsylvanian tidal rhythmites of the U.S. Midcontinent and may be used to identify freshwater inner estuarine facies, to delineate fluvio-estuarine transitions in incised valley systems, and to refine models based exclusively on lithofacies evidence.
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Comparisons between Phycosiphon incertum Fischer-Ooster (1858) and Anconichnus horizontalis Kern (1978) show that these two monotypic ichnogenera do not differ significantly in geometry, size, sediment fill, and environmental occurrence. Therefore, taxonomic priority has to be given to Phycosiphon and Anconichnus becomes a subjective junior synonym. The trace fossil is a small, highly lobed spreite structure produced by a zoned backfill consisting of a pale mantle and dark core. In muddy and homogeneous material the lobes tend to be oriented randomly, including vertically, whereas in laminated sand and silty sediments they tend to lie parallel to bedding. Textural differences between host sediment and spreite or mantle may be subtle and not always evident. Observations in modern sediments are in agreement with the type material of both ichnogenera. -from Authors
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Book
Ichnology is the study of traces created in the substrate by living organisms. This is the first book to systematically cover basic concepts and applications in both paleobiology and sedimentology, bridging the gap between the two main facets of the field. It emphasizes the importance of understanding ecologic controls on benthic fauna distribution and the role of burrowing organisms in changing their environments. A detailed analysis of the ichnology of a range of depositional environments is presented using examples from the Precambrian to the recent, and the use of trace fossils in facies analysis and sequence stratigraphy is discussed. The potential for biogenic structures to provide valuable information and solve problems in a wide range of fields is also highlighted. An invaluable resource for researchers and graduate students in paleontology, sedimentology and sequence stratigraphy, this book will also be of interest to industry professionals working in petroleum geoscience.
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Represents an update and expansion of a set of course notes previously published in 1975. Topics covered include: bed configurations; deposition and stratification; stratification sequences; fluvial deposits and facies models; conglomerates - emphasising fluvial and alluvial fan environments; stratification and sequence in prograding shoreline deposits; shallow marine environments - a comparison of some ancient and modern environments.-C.T.Baldwin
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Fluvial-estuarine channel complexes are significant producing reservoirs both onshore and offshore western Trinidad. These channel complexes are notoriously difficult to correlate in the subsurface. Numerous permeability baffles and barriers create complex reservoir heterogeneities that can result in significant bypassed hydrocarbons if the geometry and architecture of the channel bodies are incorrectly identified and not correlated in a rigorous sequence-stratigraphic framework. Outcrops of tidally influenced nonmarine channel complexes and modern depositional analogs are used to determine architectural elements and bounding surfaces that impact reservoir continuity and heterogeneity, thus, highlighting subsurface correlation pitfalls. These elements and surfaces that are established from the outcrops are used for the examination of cores, well-log, and seismic data of strata deposited in analogous depositional systems. The subsurface and the outcrop geologic models are used in two reservoir-modeling scenarios: first, to refine subsurface reservoir models for horizontal well placement, leading to a more effective depletion strategy for the reservoir, and second, the modeling of a field simulation using outcrop exposures of a channel complex as a producing analog. The result of the simulation runs was a similar recovery from the "field© with far fewer wells, showing that substantial cost reductions are possible in drilling and completions, operations, and future well and field abandonment, including the potential risk and costs for environmental remediation.
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Reveals two types of shelf-to-shoreface sequences: 1) gradational-based sequences that steadily coarsen upward from thin-bedded, wave-rippled sandstone and mudstone through hummocky cross-stratified (HCS) sandstone and mudstone into mud-free, swaley cross-stratified (SCS) sandstone capped by a root bed, and 2) sharp-based sequences that consist of SCS sandstone which, near the base, may contain large mudstone intraclasts, sharply overlying thin-bedded sandstone and mudstone. -from Author
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FULL PDF AVAILABLE ON REQUEST FROM ROGER HIGGS. The tectonic evolution of the Cenozoic mountain ranges fault systems and basins that comprise the roughly east-west Caribbean/South America plate boundary zone from Colombia to Trinidad was controlled principally by highly oblique dextral convergence between the Caribbean and South American Plates. The Caribbean Plate is pinned by the Central American and Lesser Antilles subduction zones and is stationary in a mantle reference frame whereas the South American Plate is moving westwards in that frame. The Caribbean Plate is of Pacific provenance and has since early Cenozoic time progressively invaded at an average rate of 20-25 mmlyr the Proto-Caribbean oceanic gap between North and South America. Thus, the Lesser Antilles are terminated southward by a dextral transpression zone that lengthened progressively throughout Cenozoic time. This zone showed strong partitioning between east-west dextral strike slip faults, such as the Oca and EI Pilar faults, and south-southeastward-directed thrust nappes. The nappes loaded the South American craton to generate a coupled flexural foreland basin and peripheral bulge that migrated eastwards. At any time during this evolution, the zone between the thrust complex and the crest of the peripheral bulge was a zone of potential updip hydrocarbon migration which moved eastwards in tandem with the relatively eastward migrating Caribbean Plate. In several cases, especially in Oligocene and younger Cenozoic times, E-W trending strike slip and normal faults decoupled parts of the thrust load from the South American craton and allowed flexural recovery, the rapid uplift of coast ranges, and thick sedimentation in transtensional basins. All deformation in the Venezuela nappe pile pertaining to arc-continent collision between the Caribbean and South American crusts is of Cenozoic age and youngs from west to east. Our evolutionary tectonic reconstruction of the Caribbean/South American plate boundary zone is critically dependent upon a precise restoration of the geometry of northwest South America immediately before the Caribbean Plate began its relative eastward motion. This involved our determining the amounts of relative motion along the various faults and deformation zones of Colombia and Venezuela that have developed mainly since the late Oligocene. Retro-restoring motion on these faults allows a construction of the Cenozoic nappe front prior to 25 Ma and the shape of northwest South America prior to 60 Ma. Displacements include about 110 km of sinistral motion on the Santa Marta Fault Zone, up to 150 km of dextral slip in the Merida Andes zone, 25 km of shortening across the Sierra de Perija, and at least 65 km and 90 km of dextral motion on the Oca Fault Zone in Colombia and Venezuela, respectively. On a retrodeformed paleogeographic grid which takes into account all of these restorations as well as removal of accreted terranes, the paleogeographic development of Venezuela and Trinidad is traced through Cenozoic time and important tectonic processes and controls on hydrocarbon accumulations are defined and discussed.
Chapter
Early Permian rocks of the Chase Group in north-central Oklahoma consist of repeated couplets of carbonates and clastics. The carbonates and clastics correlate to major transgressive and regressive events, respectively. The sole of the lowest (first) transgressive carbonate bed of each depositional couplet is covered with ubiquitous horizontal boxworks of the trace fossil Thalassinoides isp. Horizontal forms of the trace fossil Rhizocorallium isp. characterize the top bedding-plane surface of the highest (last) carbonate unit of each couplet, and mark the discontinuity surface at the culmination of a major transgression and the initial onset of a major regression. These trace-fossil associations are assigned to the substrate-controlled Glossifungites ichnofacies.
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Trace fossils are abundant and extremely well-preserved in the unconsolidated, siliciclastic sediments of the Late Cretaceous Englishtown Formation exposed along the Chesapeake and Delaware Canal in Delaware. The trace fossil assemblage is characteristic of a nearshore environment and can be divided into two subassemblages. The upper part of the formation is dominated by densely packed Ophiomorpha nodosa shafts and tunnels, Skolithos linearis, and a delicate branching burrow that forms vertical polygonal nets. The subassemblage that characterizes the middle and lower parts of the sequence consists of Macaronichnus segregatis and a Skolithos-like form, both of which created mottled horizons, isolated O. nodosa shafts and tunnels, Schaubcylindrichnus coronus, and probable echinoid burrows. Each trace fossil taxon is described, and modern tracemaker analogs are discussed to enable further interpretation of the trace fossils and their paleoenvironmental significane. The Englishtown Formation is interpreted to have been deposited in a prograding nearshore environment with a low energy, O. nodosa-dominated, upper shoreface - lower foreshore zone similar to parts of the modern shallow-water Sea Isles coast of Georgia. - Author
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Four coarsening upward parasequences, ranging in thickness from 4 to 17m are present in an Upper Mannville (Aptian to early Albian) core from east central Alberta. These parasequences are composed of three main facies; mudstone, mudstone/sandstone, and bioturbated rippled sandstone. Based on sedimentological, ichnological, palynological, and geochemical data these parasequences are interpreted as crevasse splay deposits. A low diversity suite of trace fossils (Arenicolites, Chondrites, Gyrolithes, Monocraterion, Palaeophycus, Planolites, Skolithos, and Teichichnus) characterize these units. The ichnological character of these deposits is unique and represents a powerful tool in the delineation and interpretation of marginal marine environments.
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In Coal Creek Canyon, Utah, the Spring Canyon Member of the Blackhawk Formation is divisible into four regressive hemicycles of deposition, each representing the downdip part of a nearshore-to-offshore sequence. The first and fourth hemicycles are best developed. Individual bedding units span middle-shoreface to lower-offshore lithofacies, the latter corresponding to a thin intertongue of Mancos Shale. Trace fossil assemblages include ~22 ichnospecies and 17 ichnogenera: Ancorichnus, Aulichnites, Chondrites, Cylindrichnus, Ophiomorpha, Palaeophycus, Phoebichnus, Planolites, Rosselia, Schaubcylindrichnus, Scolicia, Skolithos, Taenidium, Teichichnus, Terebellina, Thalassinoides , and Uchirites. Diversity and abundance of ichnospecies are greater in nearshore than in offshore lithofacies. Distal deposits are typified by obscure bioturbate textures: Cylindrichnus concentricus, Palaeophycus heberti , and Rosselia socialis are prevalent through the remainder of the lithofacies suite. Ophiomorpha irregulaire and Schaubcylindrichnus coronus are most common in middle-shoreface beds and Chondrites ichnosp. in upper-offshore beds; Ophiomorpha nodosa and O. annulata also are common in this part of the sequence.
Chapter
A composite ichnofossil is characterized by two or more discrete trace fossils belonging to different ichnotaxa that seem to be parts of a single burrow. Such specimens are recognized as a common mode of trace fossil occurrence. In many cases, composite ichnofossils represent a combination of a primary larger host structure and the subsequently produced smaller sized forms created by an infaunal deposit feeder. A peculiar specimen of a composite ichnofossil, which consists of separate elements assignable to Piscichnus waitemata and Macaronichnus isp., is described and interpreted in this chapter. The fill in the host ichnofossil P. waitemata produced by feeding behavior of rays was completely emplaced by subsequently produced Macaronichnus isp. Producers of Macaronichnus isp. that are discussed in the chapter may have invaded the Piscichnus-fill in a very short period after the production of P. waitemata and may have completely reworked the sediment in the fill. The fill in Piscichnus was utilized by the Macaronichnus-producer as a new but temporary habitat. Such a deep penetration of Macaronichnus isp. has led to an unusually high potential of preservation for this ichnofossil, which typically represents the shallowest tier ichnofossil in the studied interval.
Article
Analyses of deltaic facies successions highlight recurring ichnological patterns that reflect a variety of physicochemical stresses imposed upon infaunal organisms by the interaction of various delta-front processes. Analysis of numerous ancient deltaic deposits in Canada, the United States, Australia, and offshore Norway persistently show reductions in bioturbation intensity and impoverishment in ichnological diversity, compared to those of nondeltaic shorelines. Some facies locally demonstrate sporadic colonization and recolonization of substrates left denuded by episodic depositional conditions. Deltaic ichnological suites also locally display size reductions of ichnogenera and a paucity of suspension-feeding ethologies. Resulting trace-fossil suites are overwhelmingly dominated by deposit-feeding behaviors, even in sandy facies. Such ichnological characteristics largely reflect increased sedimentation rates and heightened fluvial discharge, which serve to impede infaunal colonization. River-derived stresses are profound: salinity changes, hypopycnal-flow-induced water turbidity, distributary flood discharges with accompanying phytodetrital (comminuted plant debris) pulses, hyperpycnal-flow-induced sediment gravity flows, and fluid-mud deposition all conspire to produce the overall depauperate nature of the ichnological assemblage. Freshet-discharge events during river floods, accompanied by hyperpycnal conditions, may lead to the episodic introduction of reduced-salinity waters immediately above the sediment–water interface in delta-front and prodelta depositional settings. Such conditions may facilitate development of synaeresis cracks and promote reductions in infaunal populations. Wave energy generally buffers fluvial effects, by dispersing suspended sediment offshore and encouraging the thorough mixing of waters of contrasting salinity. High mud concentrations near the delta front damp wave energy, however, limiting its effectiveness in remediating the benthic ecosystem, particularly immediately following distributary flood discharges and storm events. In wave-dominated settings, strong alongshore drift also operates to extend river-derived stresses considerable distances downdrift from distributary mouths. Where asymmetric deltas are formed, markedly different ichnological expressions are expressed on either side of distributary-channel mouths. Updrift settings typically retain classic shoreface assemblages, whereas downdrift environments commonly acquire markedly stressed suites. Storm energy may be effective in dispersing mud and mixing waters, but it also results in erosion and episodic sediment deposition. Concomitant precipitation induces river floods, returning river-derived stresses to the delta front. Tidal energy and its effects on the infaunal communities of deltas are poorly documented. Tidal flux may trap mud plumes against the delta front, elevating water turbidity. Pronounced mud flocculation coupled with increased settling velocity associated with tidal mixing also leads to rapid deposition of thick fluid muds, particularly in low-lying areas, hampering or precluding colonization. Tidal energy also leads to marked changes in energy and salinity near the sediment–water interface at several time scales. Deltaic ichnological suites are characterized by structures of opportunistic trophic generalists, though mainly those of facies-crossing deposit feeders. High water turbidity, particularly near the sea floor, precludes most suspension-feeding behavior, and suppresses the development of the Skolithos ichnofacies, even in many proximal delta-front deposits. Ichnological characteristics record the dynamic interplay and relative importance of these different processes, both temporally and spatially. on delta systems.
Article
Terrestrial and marine invertebrate organisms both leave records of their activities in the sediment in the form of trace fossils, at least during certain stages of their ontogeny. In contrast, trace fossils produced by vertebrate organisms are scarce, although terrestrial trace fossils provide exclusive insights into the social behaviour of their producers. In the marine realm, vertebrate trace fossils are relatively rare, difficult to identify and problematic to interpret. However, in certain settings, observations on serendipitously preserved and exposed trace fossils can shed light on the predatory behaviour of marine vertebrates. In Miocene outer shelf to nearshore sandstones of the Taliao Formation in NE Taiwan, large numbers of bowl-shaped trace fossils can be observed. Morphology and size range (diameter typically 10–30 cm, average depth around 10 cm) of these trace fossils agree well with feeding traces of modern stingrays, and the trace fossil Piscichnus waitemata, which has been attributed to bottom feeding rays. Stingrays direct a jet of water from their mouths to excavate a bowl-shaped pit to expose their prey. In the material filling the excavated bowl, broken pieces of two other common trace fossils, Ophiomorpha and Schaubcylindrichnus, are often found, and in a number of cases, vertical shafts of Ophiomorpha surrounded by dispersed pieces of wall material have been observed. In contrast, surrounding sediment rarely contains this kind of broken pieces of wall material. These observations clearly indicate that stingrays specifically targeted the producers of the trace fossils: thalassinoid crustaceans and worms, respectively. The targeted predation of these relatively deep burrowers furthermore suggests that the rays used their electroreceptive organs to locate the prey; as such, direct targeting of buried prey only based on olfactory senses has been shown to be ineffective in experiments with extant myliobatiform rays.