Temporal and spatial changes in style of accretion at the bend of a sinuous turbidite slope channel (channel–levee Complex 5, Tachrift System of NE Morocco)

Journal of Sedimentary Research, Journal Year: 2025, Volume and Issue: 95(2), P. 286 - 313

Published: March 24, 2025

Abstract This outcrop study describes variously accreted deposits constituting the fill of a sinuous channel from Tachrift System (upper Miocene Taza–Guercif Basin, NE Morocco). Detailed correlation fifty-nine logs three outcrops spanning left-turning bend allow recognition four stratigraphic units recording establishment and levee development, aggradation translation expansion, switching parent channel. Results show that lateral-accretion packages (LAPs) formed at inner bank represent main intra-channel depositional element, co-occurring with equally sandstone-rich coarse-grained outer bank. The best-exposed larger example LAPs occurs in two correlated exposures c. 500 meters apart along-stream, which most likely straddle apex. In upstream outcrop, cut-and-fill features sandstone amalgamation make it difficult to recognize lateral accretion. Here, consist bedsets amalgamated sandstones bounded by thalweg-dipping erosional surfaces are lined up mud-clast breccias deeper part fill. downstream become lithologically more layered along their profile. Moving accretion dip, LAP top, they comprise finer-grained, structured alternating mudstones. transition into mud-rich heterolithic deposit characterized trough-cross inclined stratification, dips high angle mean paleocurrent. extends over distance few hundred meters, straddling inner- outer-bank transition, is interpreted as expression bank-attached bars (here termed turbidite counter-bars) forming flow separation zone. provides insights longitudinal heterogeneity lithological composition counter never before observed outcrop.

Language: Английский

---

A tale of a changing basin - a transient model of the 7.17 event leading to the Messinian Salinity Crisis

Marine Geology, Journal Year: 2024, Volume and Issue: 470, P. 107270 - 107270

Published: March 16, 2024

Before the Messinian Salinity Crisis (MSC) left its imprint on sediment record of Mediterranean Sea in form evaporites, basin had already undergone significant changes. At 7.17 Ma, a drop δ13C values, as well basin-wide shift abundance benthic foraminifers, attest to sudden change conditions. This event coincides with an increase amplitude insolation curve. It thus stands question whether freshwater budget or connection between and Atlantic was driver for this event. Answering would not only help understand itself, but might also decipher early dynamics MSC. With computational box model, we investigate response varying wide range restriction. The results then let us define scenarios which analyse how gradually changing restriction express itself dynamics. We find that alone cannot explain changes are attributed 7.2 event, coupled most differences can be accounted for. Our show gradual provoke non-linear behaviour basin, appear abrupt when happening short enough timescale. Such enhance influence said budget. tells processes likely triggered started much earlier incrementally increased Sea.

Language: Английский

---

Grain size from source to sink – modern and ancient fining rates

Earth-Science Reviews, Journal Year: 2024, Volume and Issue: 250, P. 104699 - 104699

Published: Feb. 2, 2024

A unique synthesis of grain size-distance data is presented, comparing, for the first time, size and fining trends in a wide range modern ancient axial sediment dispersal systems, tracking grain-size from source to sink across several sedimentary basins. In general, decreases exponentially with distance down system, examples fine at broadly comparable rates similar depositional settings. Linear vary by eight orders magnitude, being higher coarser-grained Very few sets have median between 1 5 mm diameter, supporting idea that material this calibre rare. Alluvial fans highest rates, up 450 cm/km (216%/km) 115 (427%/km) examples, but more typically around 12 mm/km (87 1%/km), whereas fluvial gravels 0.8 4 (0.4 5%/km). Sand-prone systems slowly, tens microns per kilometre or less: 23 μm/km (0.25 2.5%/km) distributive ~1 8 (~1 6%/km) fluvio-deltaic channels, 0.2 44 (0.08 14%/km) ergs, 0.45 29 (0.18 7%/km) basin-plain turbidites. At basin scale, increase where pinch out down-system gravel-sand transition, sands toe shoreface. Modern transitions are relatively well characterised, ranging 71 (483 2%/km), lower wider wider, longer rivers, insights appear applicable rock record. Downstream predominantly reflects selective deposition coarser preferential transport finer grains, subsidence increasing as grains preferentially extracted up-dip form stratigraphy. Across short segments, can system result winnowing, bypass, lateral input. Comminution largely considered secondary factor important input overwhelm downstream effects, sorting dunes may obscure downwind trends. deep water, when slope bypassed, basin-floor contemporaneous 30 (5%/km), if deposited on slope, (225 75%/km) distances shorter. Axial flow lines turbidites diverse grain-size, dimension, be closely mass-balance plots, suggesting properties one bed could inform predictions those another. As yet there no studies conglomeratic deep-water transition conglomerate sand-dominated particular interest, given its importance systems. The dataset has potential constrain computer simulation models calibre, subsurface address, example, aquifer flow, petroleum migration.

Language: Английский

---

Recognizing key sedimentary facies and their distribution in mixed turbidite–contourite depositional systems: The case of the Pacific margin of the Antarctic Peninsula

Sedimentology, Journal Year: 2022, Volume and Issue: 69(4), P. 1953 - 1991

Published: Feb. 1, 2022

Abstract Interplay of deep‐water sedimentary processes is responsible for building a myriad features and deposits across mixed turbidite–contourite systems, from <5 cm beds to >200 km long drifts. Investigations the spatial temporal variability their facies associations crucial reveal dynamics between along‐slope bottom currents down‐slope turbidity currents, as well impact on drift construction channel erosion. This study focuses extensive modern (turbidite–contourite) developed continental rise Pacific margin Antarctic Peninsula. Nine sediment cores were sampled analysed, through grain size geochemical methods, at high‐resolution ( ca 1 20 cm). Three main have been identified distinct morphological (i.e. mounded drifts trunk channels), comprising intercalations hemipelagites, current reworked sands (which include fine coarse‐grained contourites) gravitational (turbidites mass‐transport deposits). These reflect fluctuations background sedimentation, oscillations bottom‐current velocity frequency gravity‐driven currents. The record cyclic alternations during Late Quaternary (>99 kyr), suggesting that variations are strongly linked glacial–interglacial cycles Marine Isotope Stages 6. Sedimentary records affected by polar margins, such those Peninsula, essential decipher sequences deposits, low degree bioturbation throughout most sediments allows us observe original structures, which poorly preserved in similar other margins.

Language: Английский

---

Bioclastic bottom‐current deposits of a Devonian contourite terrace: Facies variability and depositional architecture (Tafilalt Platform, Morocco)

Sedimentology, Journal Year: 2023, Volume and Issue: 70(5), P. 1413 - 1471

Published: Feb. 2, 2023

ABSTRACT The study examines bioclastic carbonate contourites that arise from the broad spectrum of bottom‐current related sedimentary processes ranging deposition to erosion. result intermittent accumulation sediment are thin and condensed successions with abundant hiatuses. Such deposits poorly known, since broadly accepted contourite‐facies model, bi‐gradational sequence, characterizes environments contourite depositional systems as a continuous accretion fine‐grained siliciclastic sediments. To increase current understanding facies within hiatal records, Eifelian–Frasnian Tafilalt Platform in Morocco was investigated. succession is divided into five associations interpreted reflect pelagic sedimentation bottom currents on terrace, gently inclined section upper slope Gondwana shaped by water‐mass interface. Contourite mainly controlled oxic clear‐water (documented moderately completely bioturbated limestones hydrogenetic ferromanganese nodules, low organic‐carbon contents), at times also an anoxic water mass (featured organic‐rich coquinas absent sparse bioturbation predominantly syngenetic framboidal pyrites). Biostratigraphic data overall architecture display palaeoceanographic hydrodynamic associated shifting inner terrace characterized alongslope channel small mounded drift its downslope margin. Energetic furthermore caused abraded surfaces, i.e. plain areas non‐deposition localized erosion, sandy condensation layers. microfacies reflects repeated alternation between suspension deposition, winnowing fines, bedload traction, dynamic bypassing reworking, together concomitant seafloor cementation. Coquinas planktonic nektonic organisms identified integral parts sequences showing inverse normal grading. Hiatal lag concentrations intraclasts, nodules conodonts often drape hardgrounds erosional surfaces midpoint these frequently incomplete sequences. This Devonian case provides opportunity investigate spatial temporal variability bed‐scale regard drift‐scale architecture. In addition, high‐resolution record starting point for unravelling pattern oceanic circulation greenhouse world.

Language: Английский

---

Plate convergence controls long-term full-depth circulation of the South China Sea

Marine Geology, Journal Year: 2023, Volume and Issue: 459, P. 107050 - 107050

Published: April 15, 2023

Language: Английский

---

Eocene to middle Miocene contourite deposits in Cyprus: A record of Indian Gateway evolution

Global and Planetary Change, Journal Year: 2022, Volume and Issue: 219, P. 103983 - 103983

Published: Nov. 10, 2022

Language: Английский

---

Expedition 401 Preliminary Report: Mediterranean–Atlantic Gateway Exchange

Preliminary report, Journal Year: 2024, Volume and Issue: unknown

Published: April 30, 2024

Marine gateways play a critical role in the exchange of water, heat, salt, and nutrients between oceans seas.Changes gateway geometry can significantly alter both pattern global ocean circulation climate.Today, volume dense water supplied by Atlantic-Mediterranean through Gibraltar Strait is among largest ocean.For past 5 My, this overflow has generated saline plume at intermediate depths Atlantic that deposits distinctive contouritic sediments contributes to formation North Deep Water.This single configuration only developed Early Pliocene.During Miocene, two narrow corridors linked Mediterranean Atlantic: one northern Morocco other southern Spain.Formation these followed progressive restriction closure resulted extreme salinity fluctuations Mediterranean, leading precipitation Messinian Salinity Crisis salt giant.International Ocean Discovery Program (IODP) Expedition 401 offshore drilling component Land-2-Sea proposal, Investigating Miocene Mediterranean-Atlantic Gateway Exchange (IMMAGE).Its aim recover complete record from its Late inception current targeting on either side Strait.Miocene cores precursor connections now exposed land will be obtained future International Continental Scientific Drilling (ICDP) campaigns. Plain language summaryToday, seawater takes place exclusively Strait.Around 8 million years ago, however, there were another gateways: Spain.Both have subsequently closed been tectonically uplifted preserved land.Extreme narrowing pre-Gibraltar raised substantially, more than 1 km Mediterranean's seafloor.This process may contributed major episode cooling.The chemical physical properties are key understanding quantifying cooling.International (IMMAGE).The expedition recovered records off shore Mediterranean.Future target fossil land.

Language: Английский

---

Taiwan Strait: An ocean‐current‐dominated shallow‐water setting with a river‐fed detached muddy contourite deposit

Sedimentology, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 17, 2024

ABSTRACT Contourites (contour‐current deposits) are commonly associated with deep‐water environments, but this study documents a shallow‐water, muddy contourite drift in the centre of Taiwan Strait. The body (water depths 30 to 70 m, 220 km long, 50 wide, 0 m thick), its long axis approximately colinear Strait Current, is flanked on both sides by moats. Compositional data show that composed sediment carried northward Current from Choshui River draining Taiwan. coast‐normal Changyun Ridge directly offshore splits into two branches occupy Oblique cross‐drift flow west east contributes growth. dispersal system shows down‐current fining sands ( ca 100 25 45 wide) fine‐grained elongate drift; these together represent asymmetrical subaqueous portion delta. Cores <8 kyr old, sedimentation rates up 7.8 m/ka. It coarsens upward during initial phase growth, perhaps due an increase current strength, smaller‐scale textural bedding attributed fluctuating strengths or variations wave energy depending location. Seismic southern end migrating westward, elongation Ridge, whereas middle and distal eastward because flow. Erosion eastern branch detached coeval coastal mud belt. influence tidal currents small destructive interference waves entering ends, creating weak rotary over drift. Wave within larger arriving East China Sea thought be responsible for coarsening more exposed northern end. serves as starting point developing facies model ocean‐current‐dominated straits seaways.

Language: Английский

---

Structural control and tectono-sedimentary evolution of the Gulf of Cadiz, SW Iberia since the late Miocene: Implications for contourite depositional system

Marine Geology, Journal Year: 2022, Volume and Issue: 449, P. 106818 - 106818

Published: May 16, 2022

The Gulf of Cadiz Contourite Depositional System (GCCS) developed due to the interaction Mediterranean Outflow Water (MOW) with middle continental slope SW Iberian margin. GCCS evolved in a complex tectonic setting within foreland Betic Orogeny and near Nubia-Eurasia plate boundary. This study used tectonostratigraphic analysis an extensive 2D multichannel seismic reflection dataset investigate how inherited basin configuration activity controlled sedimentary stacking pattern evolution GCCS. Three regional units (U1-U3) were recognised younger unit U3 corresponds Miocene-Quaternary system where contourite is generated. Seismic also detected dextral strike-slip Gil Eanes Fault Zone (described herein for first time), Fault, Albufeira-Guadalquivir-Doñana Basement High several diapiric structures. Integrated profiles showing these structures thickness earthquake distribution maps suggest four tectono-sedimentary domains. distinct characteristics shown by features different domains, depends at broad-scale on tectonic-control accommodation space (i.e., subsidence or uplift) local-scale presence structural highs fault-related depressions. Both influence bottom-current circulation thus deposits through late Miocene Quaternary. main stages have been evolution: 1) region was western continuation Corridor until final re-opening Strait Gibraltar (8–5.3 Ma). In this stage there predominance turbidites hemipelagic deposits, dependant activity; 2) Mediterranean-Atlantic connection onset Pliocene- Quaternary depositional (5.3–2.0 Short-term changes sedimentation during stage, from turbidite indicate periods increased 3) after transpressive regime area (from 2.0 Ma), became more homogeneous suggesting stable conditions (decrease activity) dominant deposition. work highlights remarkable events controlling seafloor relief turn influenced local oceanic processes that morphology systems.

Language: Английский

---