Ichnological analysis: A tool to characterize deep-marine processes and sediments

Earth-Science Reviews, Journal Year: 2022, Volume and Issue: 228, P. 104014 - 104014

Published: March 28, 2022

The deep-marine environment is a complex setting in which numerous processes —settling of pelagic and hemipelagic particles the water column, sediment gravity flows (downslope density currents; turbid flows), bottom currents— determine deposition, hence variety facies including pelagites/hemipelagites, contourites, turbidites hyperpycnites. Characterization differentiation among deep-sea challenge, features may be highlighted to this end: sedimentary structures, geochemical data, micropaleontological information, etc. Ichnological information has become valuable, yet some cases controversial, proxy, being most understudied. This paper gathers existing ichnological regarding frequent —from those analyses are detailed (e.g. pelagites/hemipelagites turbidites), for lacking or imprecise (hyperpycnites contourites). review palaeoenvironmental (i.e., ecological depositional) conditions associated with processes, influence these changes on tracemaker community, properties. A characterization trace fossil assemblages, ichnofabrics ichnofacies presented. Special attention paid variations features, approached through models outcrop/core scale. Similarities differences underlined facilitate differentiation. Pelagic/hemipelagic sediments completely bioturbated, showing biodeformational structures fossils, characterized by composite ichnofabrics. assemblage muddy pelagites hemipelagites mainly assigned Zoophycos ichnofacies, locally distal expression Cruziana ichnofacies. Turbidites colonized mostly from top, determining an uppermost part that entirely spotty layer; below it lies elite layer, deep-tier fossils. Turbidite beds pertain two different groups burrows, either "pre-depositional", graphogliptids, "post-depositional" traces. deposits Nereites three ichnosubfacies according parts turbiditic systems conditions. There no major content hyperpycnite classical post-depositional turbidite, nor pelagic/hemipelagic sediments, except lower ichnodiversity Trace assemblages hyperpycnites while graphogliptids scarce absent. vary within largely related conditions, depositional setting, type contourite. Ichnodiversity abundance can high, especially mud-silty contourites. contourites similar (the tiering structure probably more pelagic/hemipelagic) upper (contourites continuously bioturbated). No single archetypal would characterize

Language: Английский

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Ichnology, sedimentology, and orbital cycles in the hemipelagic Early Jurassic Laurasian Seaway (Pliensbachian, Cardigan Bay Basin, UK)

Global and Planetary Change, Journal Year: 2021, Volume and Issue: 207, P. 103648 - 103648

Published: Sept. 21, 2021

An uncommonly continuous Lower Jurassic (uppermost Sinemurian and Pliensbachian) section (Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, UK) comprises hemipelagic calcareous mudstone, wackestone/siltstone subordinate packstone/sandstone. Some beds show bigradational grading, their sedimentary structures are typical of contourite drift facies. On the basis long-term persistence stability currents that formed these deposits, sedimentation was likely controlled by thermohaline-driven geostrophic contour circulating between Boreal ocean Peri-Tethys through narrow relatively deep Basin (Cardigan Strait). Trace fossils strongly dominated Phycosiphon incertum , which produced opportunistic colonizers. Thalassinoides Schaubcylindrichnus Teichichnus common, accompanied less common Zoophycos Planolites Palaeophycus Trichichnus dwelling such as cf. Polykladichnus Siphonichnus Skolithos . The ichnofabrics usually simple, results from generally high rates deposition, unstable, water-saturated soft-ground substrate, domination well-adapted Phycosiphon, but there also cyclic appearances more complex with structures, reflecting stable bottom conditions. A new detailed analysis core has allowed cycles to be distinguished based on combination ichnological sedimentological features, pointing distinct cyclicity oceanographic mechanisms influenced orbital forcing driving inferred fluctuations in benthic life conditions, mainly variation current intensity oxygenation water reflected trace fossils. four-order hierarchy, can attributed cycles: precession obliquity (4th order), short eccentricity (3rd long (2nd order). longest (~ 2.5 Myr) 1st order is attributable longer ‟grand cycles” (period related Earth–Mars secular resonance), impacts palaeoclimatic oceanic circulation dynamics, recorded large-scale changes ichnodiversity, correlating clay minerals carbonate content. Possibly, ~ 9 Myr cyclicity, expressed observed modulation frequency eccentricity. Harmonic gives confidence signals allows refined estimation duration Pliensbachian (~8.4 jamesoni ( 2.8 Myr), ibex 2.0 davoe i 0.47 margaritatus 2.33 spinatum zones 0.8 an overall rate 4.5–5.1 cm/kyr. Obtained durations improved fit 2nd–4th cycle removes problem anomalously resulting much lower for Zone, previously obtained other methods. higher diversity noticed intervals enriched smectite; most likely, this mineral occluded pore spaces limited competition opportunist makers, allowing development other, specialized forms. continuous, expanded record deep-water hemipelagic/contour sediments sensitive climatic cycles. Strait played important role Early (at least circulation, providing a major link northern southern part Laurasian Seaway (and general domains), funneling flowing north south. • Contourite depositional system Seaway/Cardigan Orbital sea Corrected ammonite Long-term ~2.5 My driven oceanographic/climate changes.

Language: Английский

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Contourite depositional system after the exit of a strait: Case study from the late Miocene South Rifian Corridor, Morocco

Sedimentology, Journal Year: 2021, Volume and Issue: 68(7), P. 2996 - 3032

Published: April 25, 2021

Abstract Idealized facies of bottom current deposits (contourites) have been established for fine‐grained contourite drifts in modern deep‐marine sedimentary environments. Their equivalent the ancient record however are only scarcely recognized due to weathered nature most outcrop. Facies related erosional elements (i.e. channels) depositional systems not yet properly and outcrop appear non‐existent. To better understand sequences contourites, upper Miocene South Rifian Corridor (Morocco) is investigated. This system formed by dense palaeo‐Mediterranean Outflow Water. Foraminifera assemblages were used age‐constraints (7.51 7.35 Ma) determine continental slope domains. Nine based on lithology, grain‐size, structures biogenic structures. These subsequently grouped into five associations main interpreted processes (hemipelagic settling, contour currents gravity flows). The vertical succession records tectonically induced, southward migration intermittent behaviour Water, which mainly driven precession millennial‐scale climate variations. Tides substantially modulated Water a sub‐annual scale. work shows exceptional examples muddy sandy distribution model from proximal slope, channel its adjacent drift, proposed. serves as reference recognition both environments record. Furthermore, establishing hydrodynamics overflow framework provided that improves process‐based interpretation deep‐water deposits.

Language: Английский

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Trace fossil analysis of sandy clastic contouritic deposits in the late Miocene Rifian Corridor (Morocco): Ichnotaxonomical and palaeoenvironmental insights

Journal of African Earth Sciences, Journal Year: 2020, Volume and Issue: 174, P. 104054 - 104054

Published: Oct. 31, 2020

Language: Английский

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ICHNOLOGY OF MUDDY SHALLOW-WATER CONTOURITES FROM THE UPPER JURASSIC–LOWER CRETACEOUS VACA MUERTA FORMATION, ARGENTINA: IMPLICATIONS FOR TRACE-FOSSIL MODELS

Palaios, Journal Year: 2022, Volume and Issue: 37(5), P. 201 - 218

Published: May 31, 2022

ABSTRACT Contourites are increasingly being recognized in ancient fine-grained depositional environments. However, detailed ichnologic analyses focusing on shallow-water examples of these deposits scarce. The Upper Jurassic–Lower Cretaceous Vaca Muerta Formation from Argentina constitutes an important unconventional reservoir that displays dm- to m-thick, laminated, rippled and bioturbated, crinoidal mudstone fine coarse deposited by wind- thermohaline-driven contour currents. Four ichnofabrics were three facies associations. Palaeophycus heberti ichnofabric is dominant association 1, forming highly bioturbated intervals. heberti, Nereites isp., Phycosiphon incertum present 2, displaying highly, moderately sparsely intervals, respectively. This locally characterized m-thick successions comprising upward decrease then increase bioturbation index, which may have a similar origin bigradational sequences. Equilibrichnia-Fugichnia mostly occurs 3 less commonly distinctive intervals within successions. Benthic activity was controlled food distribution, oxygenation, hydrodynamic energy, water turbidity. Food delivered the surface or suspension currents, promoting deposit- suspension-feeding strategies infauna, Oxygen levels increased during current yet remained relatively low (upper dysoxic). Hydrodynamic energy intensity, resulting lower degrees higher events. Suspension-feeding suggest turbidity transport. herein example increases our understanding environmental controls supporting fact high typical contourite providing muddy contourites showing preservation sedimentary structures due oxygen deficiency bottom waters.

Language: Английский

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The Late Miocene Rifian corridor as a natural laboratory to explore a case of ichnofacies distribution in ancient gateways

Scientific Reports, Journal Year: 2021, Volume and Issue: 11(1)

Published: Feb. 18, 2021

Oceanic gateways have modulated ocean circulation and influenced climatic variations throughout the Earth´s history. During late Miocene (7.8-7.35 Ma), Atlantic Ocean Mediterranean Sea were connected through Rifian Corridor (Morocco). This gateway is one of few examples deep ancient seaways with a semi-continuous sedimentary record. Deposits comprise turbidites intercalated between deep-sea mudstone (i.e., hemipelagites drift deposits), channelized sandstone contourite facies, shallow marine sandstone. Herein an ichnological analysis was conducted in these upper sediments to improve characterisation palaeoenvironmental conditions. In addition, ichnofacies analysed elucidate how bottom currents control distribution can modify their attributes. Turbidite deposits are typified by vertical trace fossils Ophiomorpha), conforming Ophiomorpha rudis ichnosubfacies. Contouritic exhibits high density low diversity trace-fossil assemblage, predominant Macaronichnus Scolicia, resembling proximal expression Cruziana ichnofacies. Shallow environments dominated (e.g., Conichnus, Ophiomorpha, Skolithos), allowing assignation Skolithos study reveals for first time variability attributes at Corridor, associated turbidites, sediments. Hydrodynamic energy as major factor controlling maker communities studied seaway. Highly energetic conditions typical shallower settings present deeper-water slope), contributing ichnodiversity impoverishment

Language: Английский

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Deep-sea bottom currents influencing tracemaker community: An ichnological study from the NW Iberian margin

Marine Geology, Journal Year: 2021, Volume and Issue: 437, P. 106503 - 106503

Published: May 8, 2021

Language: Английский

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The complex case of Macaronichnus trace fossil affecting rock porosity

Scientific Reports, Journal Year: 2021, Volume and Issue: 11(1)

Published: Jan. 21, 2021

Abstract Bioturbation is an important factor for reservoir quality due to the modification of host rock petrophysical properties (i.e., porosity, permeability, and connectivity). However, there no predictable relationship between bioturbation its effect on properties, variability involved ichnological features. A detailed analysis necessary determine how affects in a bioturbated reservoir. Traditionally, features such as density, tiering, size, orientation, architecture, fill, have been considered. other undervalued case lining. Here, we present study effects Macaronichnus burrows, ichnotaxon usually related hydrocarbon exploration high concentration notably affecting properties. , subhorizontal cylindrical burrow, characterized by well-defined developed outer rim surrounding tube core. Our data indicates clear zonation porosity according burrow structure, with lowest core higher values associated surrounded rim. This duality determined tracemaker grain selective feeding activity consequent concentrated cementation. The organism concentrates lighter minerals fill during feeding, favoring post-depositional cementation diagenesis this results lower than rock. heavy minerals, mainly glauconite, are located rim, showing porosity. support view that analyses essential reservoirs, evidencing addition those traditionally considered must be evaluated.

Language: Английский

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Sedimentary processes in the Discovery Gap (Central–NE Atlantic): An example of a deep marine gateway

Deep Sea Research Part I Oceanographic Research Papers, Journal Year: 2021, Volume and Issue: 180, P. 103681 - 103681

Published: Nov. 29, 2021

Paleoceanographic studies of abyssal bottom currents are often complicated by low current speeds and sedimentation rates, resulting in sediment condensation or erosion. However, increased rates erosion deposition may occur where velocities change as they pass through deep marine gaps gateways. Despite this, the depositional processes these gateways their paleoceanographic implications remain poorly understood. Based on new sedimentological, hydrological geophysical (high resolution seismic bathymetry) data from Discovery Gap (Azores–Gibraltar Fracture Zone) collected during 43rd cruise R/V Akademik Nikolaj Strakhov 2019, key sedimentary occurring Late Quaternary have been determined. Two depressions with depths exceeding 5300 m centre south identified, latter filled contouritic deposits. These separated a roughly N–S trending central sill at 4860 terrace 4720 water depth. Elongated NE–SW highs sills, present north study area. Their importance controlling flow is determined presence base adjacent sheeted mounded contourite drifts. Pelagic, hemipelagic, reworked pelagic/hemipelagic fine-grained facies identified. The associations point to remarkable variability Antarctic Bottom Water (AABW), linked glacial–interglacial changes, its intermittent influence Quaternary. During glacial intervals (MIS 6, 4 2) terminations there was enhanced activity coeval higher terrigenous content, carbonate dissolution. results this improve our understanding environments highlight value record for interpreting interaction morphology. Future work other modern essential shed more light how form fully reconstruct deep-water paleocirculation within oceanic basins.

Language: Английский

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Evolution of a fluvial-dominated delta during the Oligocene of the Colombian Caribbean: Sedimentological and ichnological signatures in well-cores

Journal of South American Earth Sciences, Journal Year: 2021, Volume and Issue: 111, P. 103440 - 103440

Published: June 26, 2021

Basin analysis from Colombian Caribbean is particularly important given the interest in finding hydrocarbon reservoirs, but their complex geological evolution, and frequent lateral vertical variation of facies difficult a conclusive characterization, highlights need for detailed sedimentological ichnological studies. The study succession corresponds to an interval well core drilled south Sinú-San Jacinto (Colombian Caribbean), with 1069 ft (~326 m) thick Oligocene siliciclastic succession, interpreted general terms, as deposited deltaic system. integrated sedimentological/ichnological allows differentiation dominant facies, predominant lithologies such conglomerates, sandstones, mudrocks, bioclastic sediments, coal beds. assemblage low abundance moderately diverse, composed by Conichnus, Cylindrichnus, Dactyloidites, Macaronichnus, Ophiomorpha, Phycosiphon, Skolithos, Taenidium, Teichichnus, Thalassinoides, rhizoliths. complexity sedimentary system reflected its evolution throughout Oligocene. A type coarsening-upward trend was identified it repeated through studied. It presents sediments (bioclastic sandstones mudrocks) that pass into horizontal lamination massive mudrocks occasionally bioturbated interbedded lenticular bedding, occurrence Teichichnus. Above, muddy rarely planar cross-lamination, Thalassinoides are registered. Transition carbonaceous medium beds, fine-to coarse-grained sometimes Macaronichnus and/or Ophiomorpha observed. Towards top, observed This interrupted bioturbation index generated exclusive Taenidium. Massive erosive bases, asymmetrical ripples, high content organic debris recorded. reflects progradational similar those fluvial-dominated sequences. Detailed revealed even fluvial processes were system; however, local tidal wave influence Moreover, integration information characterizing different sub-environments system, prodelta bay, distal delta front, proximal distributary channels, mouth bars, lower plain, this essential areas economic interest.

Language: Английский

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