Environmental Conditions in the Pre-jenkyns Event Times (Late Pliensbachian – Early Toarcian) in the Southiberian Palaeomargin (Betic External Zones, Southern Spain)

Research Square (Research Square), Journal Year: 2024, Volume and Issue: unknown

Published: April 8, 2024

Three stratigraphic sections of the Betic External Zones have been studied, two from Median Subbetic (PEL and PR) one (CE). The upper Pliensbachian materials transition to lower Toarcian dated with calcareous nannofossils in PEL PR this paper, while CE section, previous ammonite nannofossil biostratigraphies considered. dominant facies are alternance marly limestone - marl, although is represented by marls, where Jenkyns Event has recorded. In terms ichnofossils, section Macaronichnus predominates. sections, ichnoassemblages dominated Planolites, Thalassinoides Chondrites. Therefore, ichnofacies observed were generated pelagic or hemipelagic marine environments. Analysis correlation between δ¹³C δ¹⁸O each them Sr Fe/Ca Sr/Ca, as well Z-factor, indicate that geochemical signal not modified diagenesis. ratios do allow clearly identify isotopic events, except was proxies used study detritism (Zr/Rb, Sr/Cu, CIA C-value) show trends opposite those detected other Tethys even them. These peculiarities data interpreted result opening Hispanic Corridor, mixing Panthalassa seawaters extensional tectonics, which favoured development half grabens significant differential subsidence, especially during NJT5b Subzone (latest Pliensbachian). could be affected contourite currents according assemblage some these sections.

Language: Английский

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Ichnological record in gateways and other high-energy deepwater environments: a palaeo- and neoichnological approach

Geological Society London Special Publications, Journal Year: 2024, Volume and Issue: 553(1)

Published: Aug. 22, 2024

The evolution of gateways determines variations in palaeoenvironmental (ecological and depositional) conditions affecting tracemaker communities, hence biogenic structures. With respect to palaeogateways, bottom currents associated deposits (i.e. contourites) may be approached through trace-fossil studies. Ichnological analysis – individual ichnotaxa changes ichnofacies Late Miocene contourites facies from the Rifian Corridor palaeogateway (Morocco) reveals a major impact food supply, flow velocity, seafloor heterogeneity hydrodynamic energy. fact that Eocene middle deep-marine deposits, mainly contourites, nearby Indian (Cyprus) show replacement is evidence increased bottom-current velocity with sea-level variations. Moreover, ichnofabric reflect pelagic, gravitational processes simultaneously influence sedimentation. Changes composition both areas, shape burrows, intermittent governed contourite deposition. Neoichnological studies complement validate record high-energy deep-sea environments can occur palaeogateways. Modern traces ( lebensspuren ) observed on variable features (e.g. diversity, density, morphology) depending type disturbance exert trace-making benthic fauna. Parameters such as substrate consistency, nutrient availability/distribution duration intensity energetic events play role determining features. We conclude an integrative palaeo- neoichnological approach powerful tool when used improve our knowledge ecosystems gateways.

Language: Английский

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Environmental conditions in the pre-Jenkyns event times (late Pliensbachian—early Toarcian) in the South Iberian Palaeomargin (Betic External Zones, Southern Spain)

Journal of Iberian Geology, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 18, 2024

Abstract Three stratigraphic sections of the Betic External Zones were studied, two from Median Subbetic (PEL and PR) one (CE). The upper Pliensbachian materials transition to lower Toarcian dated with calcareous nannofossils in PEL PR this paper, while CE section, previous ammonite nannofossil biostratigraphies considered. dominant facies are alternance marly limestone—marl, although is represented by marls, where Jenkyns Event has been recorded. In terms ichnofossils, section Macaronichnus predominates. sections, ichnoassemblages dominated Planolites , Thalassinoides Chondrites . ichnofacies distinguished formed pelagic or hemipelagic marine environments. Analysis correlation between δ 13 C 18 O each them Sr Fe/Ca Sr/Ca, as well Z-factor, indicate that geochemical signal not modified diagenesis. ratios do allow clearly identify isotopic events, except was proxies used study detritism (Zr/Rb, Sr/Cu, Chemical Index Alteration, CIA, C-value) show trends opposite those detected other Tethys even them. These peculiarities data interpreted result opening Hispanic Corridor, mixing Panthalassa seawaters extensional tectonics, which favoured development half grabens significant differential subsidence, especially during NJT5b Subzone (latest Pliensbachian). could be affected contourite currents according assemblage some these sections.

Language: Английский

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

Journal of Sedimentary Research, Journal Year: 2021, Volume and Issue: 91(11), P. 1151 - 1165

Published: Nov. 12, 2021

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). Eocene Lefkara Formation at the Petra Tou Romiou beach section (Cyprus) shows incidence distal turbiditic episodes in a context sedimentation. Trace-fossil analysis this section, using an ichnofabric approach (i.e., ichnodiversity, Bioturbation Index, Bedding Plane Horizontal Index crosscutting relationships), was conducted to precisely describe paleoenvironmental conditions setting. Ichnofabric allow characterization differentiation sporadic events that disrupted both contourite deposition. Calciturbidite intervals show ichnofabrics consisting postdepositional U-shaped traces Arenicolites isp., ?Diplocraterion isp.,) borings typical consolidated substrates. High-energy sandy deposits are dominated horizontal deposit-feeder development with Planolites Thalassinoides isp. record slightly deformed interbeds contourites or transition between facies reveals variations bi-gradational succession, can potentially act as indicator depositional hiatus.

Language: Английский

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Exploring Ichnofacies Distribution in Ancient Seaways: The Late Miocene Rifian Corridor as a Natural Laboratory

Research Square (Research Square), Journal Year: 2020, Volume and Issue: unknown

Published: Dec. 9, 2020

Abstract 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 fine grain sediments (i.e., hemipelagites drift deposits), channelized sandstone contourite facies, shallow marine sandstones. Herein an ichnological analysis was conducted in these upper to improve characterisation palaeoenvironmental conditions. In addition, ichnofacies analysed elucidate how bottom currents control distribution can modified their attributes. Turbidite deposits are typified by vertical trace fossils Ophiomorpha ), conforming rudis ichnosubfacies. Contouritic sandstones exhibit high density low diverse fossil assemblage, predominant Macaronichnus Scolicia , resembling proximal expression Cruziana ichnofacies. Shallow environments dominated (e.g., Conichnus Skolithos allowing assignation study reveals energy be major controlling factor determining attributes seaways. Within seaways, highly energetic conditions typical shallower settings present deeper slope), contributing ichnodiversity impoverishment

Language: Английский

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