Ichnofabric analysis as a tool for characterization and differentiation between calcareous contourites and calciturbidites

2021 ◽  
Vol 91 (11) ◽  
pp. 1151-1165
Author(s):  
Olmo Miguez-Salas ◽  
Francisco J. RodrÍguez-Tovar
Keyword(s):  
Bedding Plane ◽  
High Energy ◽  
Trace Fossil ◽  
Deposit Feeder ◽  
Bottom Currents ◽  
Marine Sedimentation ◽  
Gravity Flows ◽  
Sandy Contourites

ABSTRACT The Eocene–Miocene Cyprus paleoslope system records complex deep-marine sedimentation comprising background vertical settling of autochthonous pelagic–hemipelagic particles (chalks) which were punctuated by calcareous bottom currents (contourites) and gravity flows (calciturbidites). The Eocene Lefkara Formation at the Petra Tou Romiou beach section (Cyprus) shows the incidence of deep-marine bottom currents and distal turbiditic episodes in a context of pelagic–hemipelagic sedimentation. Trace-fossil analysis of this section, using an ichnofabric approach (i.e., ichnodiversity, Bioturbation Index, Bedding Plane Horizontal Index and crosscutting relationships), was conducted to precisely describe the paleoenvironmental conditions of this complex setting. Ichnofabric analysis allow the characterization and differentiation of sporadic turbiditic events that disrupted both pelagic–hemipelagic and contourite deposition. Calciturbidite intervals show ichnofabrics consisting of postdepositional U-shaped traces (i.e., Arenicolites isp., ?Diplocraterion isp.,) and vertical borings typical of consolidated substrates. High-energy sandy contourite deposits are dominated by horizontal deposit-feeder traces and the development of ichnofabrics with Planolites isp., and Thalassinoides isp. The record of ichnofabrics with slightly deformed Planolites in the interbeds of sandy contourites or in the transition between the facies reveals variations in sedimentation in the bi-gradational contourite succession, and can potentially act as an indicator of depositional hiatus.

scholarly journals The Mesoproterozoic Stac Fada Member, NW Scotland: an impact origin confirmed but refined

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-056
Author(s):  
G. R. Osinski ◽  
L. Ferrière ◽  
P. J. A. Hill ◽  
A. R. Prave ◽  
L. J. Preston ◽  
...  
Keyword(s):  
Volcanic Eruptions ◽  
High Energy ◽  
Impact Structure ◽  
Gravity Flows ◽  
Impact Ejecta ◽  
Ejecta Blanket ◽  
Chicxulub Impact ◽  
Melted Material ◽  
Impact Origin ◽  
Primary Impact

The origin of the Stac Fada Member has been debated for decades with several early hypotheses being proposed, but all invoking some connection to volcanic activity. In 2008, the discovery of shocked quartz led to the hypothesis that the Stac Fada Member represents part the continuous ejecta blanket of a meteorite impact crater, the location of which was, and remains, unknown. In this paper, we confirm the presence of shock-metamorphosed and -melted material in the Stac Fada Member; however, we also show that its properties are unlike any other confirmed and well documented proximal impact ejecta deposits on Earth. Instead, the properties of the Stac Fada Member are most similar to the Onaping Formation of the Sudbury impact structure (Canada) and impact melt-bearing breccias from the Chicxulub impact structure (Mexico). We thus propose that, like the Sudbury and Chicxulub deposits, Melt Fuel Coolant Interactions – akin to what occur during phreatomagmatic volcanic eruptions – played a fundamental role in the origin of the Stac Fada Member. We conclude that these rocks are not primary impact ejecta but instead were deposited beyond the extent of the continuous ejecta blanket as high-energy ground-hugging sediment gravity flows.

scholarly journals Hybrid turbidite-drift channel complexes: An integrated multiscale model

Geology ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 562-568 ◽  
Author(s):  
A. Fuhrmann ◽  
I.A. Kane ◽  
M.A. Clare ◽  
R.A. Ferguson ◽  
E. Schomacker ◽  
...  
Keyword(s):  
Sediment Transport ◽  
High Resolution ◽  
Large Scale ◽  
Sediment Accumulation ◽  
Multiscale Model ◽  
Transport Processes ◽  
Bottom Current ◽  
Oceanic Circulation ◽  
Bottom Currents ◽  
Gravity Flows

Abstract The interaction of deep-marine bottom currents with episodic, unsteady sediment gravity flows affects global sediment transport, forms climate archives, and controls the evolution of continental slopes. Despite their importance, contradictory hypotheses for reconstructing past flow regimes have arisen from a paucity of studies and the lack of direct monitoring of such hybrid systems. Here, we address this controversy by analyzing deposits, high-resolution seafloor data, and near-bed current measurements from two sites where eastward-flowing gravity flows interact(ed) with northward-flowing bottom currents. Extensive seismic and core data from offshore Tanzania reveal a 1650-m-thick asymmetric hybrid channel levee-drift system, deposited over a period of ∼20 m.y. (Upper Cretaceous to Paleocene). High-resolution modern seafloor data from offshore Mozambique reveal similar asymmetric channel geometries, which are related to northward-flowing near-bed currents with measured velocities of up to 1.4 m/s. Higher sediment accumulation occurs on the downstream flank of channel margins (with respect to bottom currents), with inhibited deposition or scouring on the upstream flank (where velocities are highest). Toes of the drift deposits, consisting of thick laminated muddy siltstone, which progressively step back into the channel axis over time, result in an interfingering relationship with the sandstone-dominated channel fill. Bottom-current flow directions contrast with those of previous models, which lacked direct current measurements or paleoflow indicators. We finally show how large-scale depositional architecture is built through the temporally variable coupling of these two globally important sediment transport processes. Our findings enable more-robust reconstructions of past oceanic circulation and diagnosis of ancient hybrid turbidite-drift systems.

A new spreite trace fossil from Lower Cretaceous limestone (Western Carpathians, Slovakia)

2009 ◽  
Vol 100 (04) ◽  
pp. 417-427 ◽  
Author(s):  
Jozef Michalík ◽  
Vladimír Šimo
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Linear Form ◽  
Lower Cretaceous ◽  
Trace Fossil ◽  
Deposit Feeder ◽  
Western Carpathians ◽  
Carbonate Sediments ◽  
Intrashelf Basin

ABSTRACTZavitokichnus fusiformisn. igen. et n. isp. occurs in Lower Cretaceous (Valanginian to Hauterivian) limestones of the Fatric Superunit in the Western Carpathians. Typical cross sections of this more or less spiral trace fossil are sometimes U–O–C–S-shaped. In cross-section the trace fossil passes from a simple linear form, and spreads to a wider rolled-up or rolled-out form and then it returns to a linear trace. Spreite-like lamellae are distinguishable on several cross-section examples. The trace fossil was produced by a deposit feeder and it might be classified as a fodinichnion.Z. fusiformisco-occurs with trace fossil associations ofZoophycos,Chondrites,Planolites,HormosiroideaandPalaeophycusin carbonate sediments of a deep-seated ramp along the margin of the Fatric intrashelf basin.

Cannibalism of contourites by gravity flows: explanation of the facies distribution of the Ordovician Pingliang Formation along the southern margin of the Ordos Basin, China

2020 ◽  
Vol 57 (3) ◽  
pp. 331-347
Author(s):  
Hua Li ◽  
A.J. van Loon ◽  
Youbin He
Keyword(s):  
Ordos Basin ◽  
High Energy ◽  
Middle Part ◽  
Turbidity Currents ◽  
Middle Ordovician ◽  
Fine Grained ◽  
Southern Margin ◽  
Gravity Flows ◽  
Facies Associations ◽  
The Ordos Basin

The Late Ordovician Pingliang Formation accumulated along the southern margin of the Ordos Basin in China. The convergence of the Yangtze Plate and Sino-Korean Plate led to a trench–arc–basin system during the Middle Ordovician, with a platform- and slope-dominated setting in the east where a graben complicated the overall simple paleogeographical picture, relatively parallel zones of a platform and a slope setting in the middle, and a change from platform to slope to deep marine to a trench setting in the west. This configuration resulted in various types of gravity flow deposits and contourites with different compositions and pathways. The present study focuses on the typical characteristics of contourites in the geological record and the relationships between contour currents and gravity flows. The Pingliang Formation contains eleven lithofacies grouped into five facies associations. These facies associations represent deep sea autochthonous deposits, several types of debrites, turbidites, and contourites, as well as turbidites within which the fine-grained top portion was reworked by a contour current. The various lithofacies are concentrated in different parts of the study area: micritic contourites and debrites are concentrated in the eastern part; debrites, and sandstone and siltstone turbidites are concentrated in the middle part; and calcarenitic turbidites, contourites, and reworked turbidites occur in the western part. The main contour current ran parallel to the contour lines from east to west. Although most of the contour current continually moved westward in the eastern part of the study area, a minor part split off and followed a semicircular pathway through the Fuping Graben; its velocity became reduced here so that micritic contourites were deposited. The velocity of the contour current was increased locally when it entered a confined trough in the western part of the study area. The relatively high energy of the contour current here resulted in calcarenitic contourites. The velocity of the contour current was low where it ran through an open environment, resulting in fine-grained, thin contourites in the middle part of the study area. Large turbidity currents and debris flows occurred here, and their high energy destroyed almost all earlier deposited contourites. This explains why traces of contour currents in the middle part of the study are very scarce, although the east–west-running contour current must have passed through this area.

Holocene environmental change in a marine-estuarine-lacustrine sediment sequence, King George Island, South Shetland Islands

1996 ◽  
Vol 8 (4) ◽  
pp. 313-322 ◽  
Author(s):  
J.C. Martinez-Macchiavello ◽  
A. Tatur ◽  
S. Servant-Vildary ◽  
R. Del Valle
Keyword(s):  
Late Holocene ◽  
Volcanic Ash ◽  
Lacustrine Sediments ◽  
High Energy ◽  
South Shetland Islands ◽  
Shetland Islands ◽  
Marine Sand ◽  
Gravity Flows ◽  
And Cluster Analysis ◽  
Freshwater Diatom

Sedimentological features and cluster analysis of diatom assemblages were used to investigate a local Holocene prograding sequence of marine-estuarine-lacustrine sediments. It consists of upward finning and thinning sediment cycles formed at the mouth of a meltwater stream during regional isostatic uplift, which followed early Holocene deglaciation and marine inundation events. The sequence begins in the lower Holocene sublittoral sand (marine diatoms and abundant molluscs) overlying, with a transgressive base, the deltic (?) clastic sediment marking probably one of the pre-Holocene interglacial periods (index diatom Actinocyclus ingens suggests an age >0.62 Ma). The lower Holocene marine sand was truncated by middle Holocene gravity flows, bearing volcanic ash. They were deposited in a high energy estuarine environment (brackish diatoms). The beach subsequently formed separated the estuary from the sea and changed it into a freshwater lake. Accumulation of moss and gyttja, containing a freshwater diatom assemblage, marks the final late Holocene stage of this coastal sedimentary sequence, which can be considered as typical for deglaciation periods in the maritime Antarctic.

scholarly journals The turbidite-contourite-tidalite-baroclinite-hybridite problem: orthodoxy vs. empirical evidence behind the “Bouma Sequence”

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
G. Shanmugam
Keyword(s):  
Deep Water ◽  
General Term ◽  
Bottom Current ◽  
Turbidity Currents ◽  
Facies Model ◽  
Bottom Currents ◽  
Gravity Flows ◽  
Slope Flow ◽  
Baroclinic Currents ◽  
Facies Models

AbstractThe underpinning problems of deep-water facies still remain unresolved. (1) The Tb, Tc, and Td divisions of the turbidite facies model, with traction structures, are an integral part of the “Bouma Sequence” (Ta, Tb, Tc, Td, Te). However, deposits of thermohaline contour currents, wind-driven bottom currents, deep-marine tidal currents, and baroclinic currents (internal waves and tides) also develop discrete rippled units, mimicking Tc. (2) The application of “cut-out” logic of sequences, which was originally introduced for the “Bouma Sequence”, with sharp basal contacts and sandy divisions containing well-developed traction structures, to muddy contorts with gradational basal contacts and an absence of well-developed traction structures is incongruent. (3) The presence of five internal divisions and hiatus in the muddy contoured facies model is in dispute. (4) Intersection of along slope contour currents with down slope sediment-gravity flows, triggering hybrid flows, also develops traction structures. (5) The comparison of genuine hybrid flows with down slope flow transformation of gravity flows is inconsistent with etymology of the term “hybrid”. (6) A reexamination of the Annot Sandstone at the Peira Cava type locality in SE France fails to validate either the orthodoxy of five internal divisions of the “Bouma Sequence” or their origin by turbidity currents. For example, the “Ta” division is composed of amalgamated units with inverse grading and floating mudstone clasts, suggesting a mass-transport deposit (MTD). The “Tb” and “Tc” divisions are composed of double mud layers and sigmoidal cross bedding, respectively, which suggest a tidalite origin. (7) Although it was reasonable to introduce a simplistic “Bouma Sequence” in 1962, at a time of limited knowledge on deep-water processes, it is obsolete now in 2021 to apply this model to the rock record amid a wealth of new knowledge. (8) The disconnect between 12 observed, but questionable, modern turbidity currents and over 10,000 interpreted ancient turbidites defies the doctrine of uniformitarianism. This disconnect is attributed to routine application of genetic facies models, without a pragmatic interpretation of empirical data. (9) A suggested solution to these problems is to interpret traction structures in the sedimentary record pragmatically on the basis of empirical field and experimental evidence, without any built-in bias using facies models, such as the “Bouma Sequence”. (10) Until reliable criteria are developed to distinguish traction structures of each type of bottom currents based on uniformitarianism, a general term “BCRS” (i.e., bottom-current reworked sands) is appropriate for deposits of all four kinds of bottom currents.

Ophiomorpha irregulaire(Trace Fossil): Redescription from the Cretaceous of the Book Cliffs and Wasatch Plateau, Utah

1998 ◽  
Vol 72 (4) ◽  
pp. 773-778 ◽  
Author(s):  
Richard G. Bromley ◽  
A. A. Ekdale
Keyword(s):  
Upper Cretaceous ◽  
Trace Fossil ◽  
Deposit Feeder ◽  
Type Locality ◽  
Type Specimens ◽  
Delta Front ◽  
Book Cliffs ◽  
Fine Grained ◽  
Wasatch Plateau ◽  
Emended Diagnosis

The trace fossilOphiomorpha irregulaireFrey, Howard and Pryor, 1978, has been described chiefly from the Campanian (Upper Cretaceous) of the Book Cliffs of Carbon County, central Utah, U.S.A. Owing to the lack of type specimens and a well-defined type locality, a neotype and new paratypes are designated. Abundant material in the Spring Canyon Member of the Blackhawk Formation at Coal Creek Canyon, Book Cliffs, serves to supply a type locality and allows a more detailed description of the trace fossil than has been available hitherto, leading to an emended diagnosis. At the type locality,O. irregulaireis a shallow-tier trace fossil occurring in marine, delta-front or back-barrier, muddy, fine-grained sandstone. It probably represents the work of a crustacean deposit feeder.

Trace Fossils with Spreiten from the Late Ediacaran Nama Group, Namibia: Complex Feeding Patterns Five Million Years Before the Precambrian–Cambrian Boundary

2014 ◽  
Vol 88 (2) ◽  
pp. 299-308 ◽  
Author(s):  
Francis A. Macdonald ◽  
Sara B. Pruss ◽  
Justin V. Strauss
Keyword(s):  
Shallow Water ◽  
Feeding Habits ◽  
Bedding Plane ◽  
Trace Fossils ◽  
Trace Fossil ◽  
Outer Tube ◽  
Feeding Patterns ◽  
Large Complex

Here we describe large, complex trace fossils in the late Ediacaran Omkyk Member of the Zaris Formation, Nama Group, southern Namibia. The horizontal trace fossils are preserved on a number of talus blocks from a bedding plane of a cm-thick sandstone lens from a single stratigraphic horizon less than 100 m below an ash bed dated at 547.3 ± 0.7 Ma. The forms consist of overlapping U-shaped spreiten elements with parallel limbs surrounded by an outer tube. Individual U-shaped elements are 0.2 to 1 cm in diameter, the outer tube is less than 3 mm in diameter, and the forms as a whole range from 5 to 30 cm long and 3 to 10 cm wide. The specimens commonly show a change in direction and change in diameter. The morphology of these trace fossils is comparable to backfill structures, particularly specimens of Paleozoic Zoophycos from shallow water environments. Here we interpret these horizontal spreiten-burrows to record the grazing of the trace-maker on or below a textured organic surface. The identification of large late Ediacaran trace fossils is consistent with recent reports of backfilled horizontal burrows below the Precambrian–Cambrian boundary and is suggestive of the appearance of complex feeding habits prior to the Cambrian trace fossil explosion.

scholarly journals A possible archaeopriapulid trace fossil from the Middle Cambrian Stephen Formation, British Columbia

1992 ◽  
Vol 6 ◽  
pp. 255-255 ◽  
Author(s):  
David M. Rudkin
Keyword(s):  
British Columbia ◽  
Short Distance ◽  
Bedding Plane ◽  
Trace Fossil ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Burrowing Behaviour ◽  
Body Fossil

It is generally accepted that the extraordinary preservation of fossils in the Burgess Shale is at least partly due to the exclusion of large metazoan scavengers through rapid burial in an inimical environment. Disruption of individual organisms appears to have been largely the result of mechanical processes and/or microbial decay. The absence of bioturbation through much of the classic section, including Walcott's Phyllopod Bed, supports these arguments. However, macroscopic traces are known from other horizons within the Burgess Shale section and from lateral equivalents in the Stephen Formation a short distance south of the main locality.The sparse ichnoassemblage includes bedding-plane exposures of portions of compacted, parallel-sided burrows containing skeletal debris comprising fragmented and disarticulated hyoliths, small trilobites, and bracniopods. Walcott originally figured one such trace as Planolites sp. ? and noted, but offered no evidence for, an association with the archaeopriapulid Ottoia prolifica. This notion was subsequently rejected by Conway Morris.A recently collected specimen, from talus south of the main locality, contains a poorly preserved but recognizable body fossil of Ottoia within the outline of a “Planolites”. Although this juxtaposition may be accidental, a number of features of the association, and a consideration of the burrowing behaviour of modern priapulids, suggest that Ottoia could have been the generator of “Planolites”-like traces.

Polycylindrichnus: possible Silurian tunicate burrows from southern Ontario

1980 ◽  
Vol 17 (6) ◽  
pp. 738-743 ◽  
Author(s):  
Judith A. Fournier ◽  
S. George Pemberton ◽  
Michael J. Risk
Keyword(s):  
Bedding Plane ◽  
Trace Fossil ◽  
Common Source ◽  
Southern Ontario

Several specimens of a new trace fossil, Polycylindrichnus prolifer, n. gen., n. sp., have been collected from the Middle Silurian Thorold Formation in Hamilton, Ontario. Traces are multiple burrows, originating from a common source at depth, budding into several cylindrical to conical, subhorizontal burrows. Burrow openings lie on a common bedding plane. Traces are tentatively attributed to the activities of infaunal tunicates.

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