Sedimentary and Diagenetic Controls across the Cretaceous—Paleogene Transition: New Paleoenvironmental Insights of the External Ionian Zone from the Pelagic Carbonates of the Gardiki Section (Epirus, Western Greece)

Journal of Marine Science and Engineering, Journal Year: 2022, Volume and Issue: 10(12), P. 1948 - 1948

Published: Dec. 8, 2022

Field investigation, biostratigraphic, paleoecological, and sedimentary microfacies analyses, as well diagenetic processes characterization, were carried out in the Epirus region (Western Ionian Basin) to define depositional environments further decipher history of Late Cretaceous–Early Paleocene carbonate succession western continental Greece. Planktonic foraminiferal biostratigraphy studied carbonates revealed that investigated part Gardiki section covers Cretaceous–Paleogene (K-Pg) transition, partly reflecting Senonian limestone calciturbidites formations zone stratigraphy. Litho-and bio-facies analyses allowed for recognition three distinct facies: (a) latest Maastrichtian pelagic biomicrite mudstone with situ planktonic foraminifera, radiolarians, filaments, (b) a packstone abundant foraminifera at K-Pg boundary, (c) an early wackestone veins, micritized mixed fauna terms reworked (aberrant or broken) foraminifera. The documented facies characterize relatively low medium energy deep environment, representing transition from basin shelf toe slope crossing boundary. Micropaleontological paleoecological samples demonstrate primary productivity collapse is key proximate cause this extinction event. Additional petrographic showed petrophysical behavior reservoir characteristics study deposits are controlled by environment (marine, meteoric, burial diagenetic) influenced such micritization, compaction, cementation, dissolution, fracturing.

Language: Английский

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Stratigraphic paleobiology

Paleobiology, Journal Year: 2024, Volume and Issue: unknown, P. 1 - 18

Published: March 7, 2024

Abstract Stratigraphic paleobiology uses a modern understanding of the construction stratigraphic record—from beds to depositional sequences sedimentary basins—to interpret patterns and guide sampling strategies in fossil record. Over past 25 years, its principles have been established primarily through forward numerical modeling, originally shallow-marine systems more recently nonmarine systems. Predictions these models tested outcrop-scale basin-scale field studies, which also revealed new insights. At multi-basin global scales, joint development biotic records has come largely from macrostratigraphy, analysis gap-bound packages rock. Here, we present recent advances six major areas paleobiology, including critical tests Po Plain Italy, mass extinctions recoveries, contrasts systems, interrelationships habitats architecture, large-scale assembly regional ecosystems. We highlight potential for future research that applies paleobiological concepts studies climate change, geochemistry, phylogenetics, structure conclude with need thinking paleobiology.

Language: Английский

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Bioturbation increases time averaging despite promoting shell disintegration: a test using anthropogenic gradients in sediment accumulation and burrowing on the southern California shelf

Paleobiology, Journal Year: 2024, Volume and Issue: unknown, P. 1 - 28

Published: Nov. 7, 2024

Abstract Bioturbation can increase time averaging by downward and upward movements of young old shells within the entire mixed layer accelerating burial into a sequestration zone (SZ), allowing them to bypass uppermost taphonomically active (TAZ). However, bioturbation shell disintegration concurrently, neutralizing positive effects mixing on averaging. Bioirrigation oxygenated pore-water promotes carbonate dissolution in TAZ, biomixing itself mill weakened or microbial maceration, and/or expose damage at sediment–water interface. Here, we fit transition rate matrices bivalve age–frequency distributions from four sediment cores southern California middle shelf (50–75 m) assess competing averaging, exploiting strong gradient rates accumulation created historic wastewater pollution. We find that covaries positively with all sites, accord scenario where ultimately fuels disintegration. Both decline abruptly base 20- 40-cm-thick, age-homogenized surface three well-bioturbated despite different accumulation. In contrast, are very low upper 25 cm an effluent site legacy toxicity, recolonization bioirrigating lucinid bivalves. Assemblages formed during maximum emissions vary strongly millennial scales low-sediment non-effluent centennial scale was high but recovered quickly, decadal second high-sedimentation remained for decades. Thus, even though covary rates, reducing postmortem survival, has net effect increasing skeletal remains this warm-temperate siliciclastic shelf.

Language: Английский

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Middle Devonian brachiopod-hosted sclerobiont assemblage from the northern shelf of Gondwana (Mader Basin, Morocco): Diversity, colonization patterns and relation to coeval palaeocommunities

Palaeogeography Palaeoclimatology Palaeoecology, Journal Year: 2022, Volume and Issue: 594, P. 110947 - 110947

Published: March 24, 2022

Middle Devonian (Eifelian/Givetian transition) brachiopod-hosted sclerobiont assemblage from Gondwana (Morocco, eastern Anti-Atlas, Mader Basin) has been studied for the first time. The analysis of hundreds brachiopod shells revealed at least 26 taxa, making palaeoecommunity one most diverse reported to date. palaeocommunity is dominated by encrusting organisms, in particular bryozoans, foraminifers, ascodictyids and microconchids, whereas bioeroders are represented Clionolithes Oichnus ichnospecies. As supported microfacies, fossil preservation presence Rothpletzella algae, sclerobionts developed a calm, euphotic, offshore marine environment situated below normal wave base. Prevalence articulated without signs either extensive mineral staining, or taphonomic alteration resulting hydrodynamic processes, as well some delicate encrusters (Vinella, Rothpletzella), indicate that did not undergo time-averaging. hosts were colonized syn vivo, evidenced epibiont growth near commissure margin, shell malformations even embedded auloporid corals cornulitid tubeworms. Competition space among was apparently limited, suggested very low number overgrowth interactions, indicating shelly substrate available colonization abundant. same dominant groups on different host taxa indicates lack species-selectivity these colonizing sclerobionts. It also suggests species pool generally similar throughout deposition sampled rock interval. testified bryozoan species, this locality northern had strong affinities with those southern margin Laurussia, likely reflecting connectivity between regions provided South Equatorial – North current system during late Eifelian Kačák transgressive episode.

Language: Английский

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A downcore increase in time averaging is the null expectation from the transit of death assemblages through a mixed layer

Paleobiology, Journal Year: 2023, Volume and Issue: 49(3), P. 527 - 562

Published: Jan. 19, 2023

Abstract Understanding how time averaging changes during burial is essential for using Holocene and Anthropocene cores to analyze ecosystem change, given the many ways in which affects biodiversity measures. Here, we use transition-rate matrices explore extent of downcore as shells transit through a taphonomically complex mixed layer into permanently buried historical layers: this null model, without any temporal rates sedimentation or bioturbation, contrast with patterns that might be produced by human activity. Assuming stochastic exhumation movements between increments within disintegration increments, find almost all combinations net sedimentation, mixing, produce increase (interquartile range [IQR] shell ages), trend typically associated decrease kurtosis skewness shift from right-skewed symmetrical age distributions. A thus expectation wherever bioturbation generates an internally structured (i.e., surface, well-mixed underlain incompletely layer): under these conditions, are throughout entire at slower rate than they below it sedimentation. This created mixing further amplified decline rate. We accurately reproduce IQR, skewness, observed bivalve assemblages southern California shelf. The age-frequency distributions typical surface death assemblages—the focus most actualistic research—might fossilized exceptional conditions episodic anoxia sudden burial. However, such will not survive subsurface geologically transient. deep-time fossil record dominated instead more time-averaged weakly skewed form lower parts layer.

Language: Английский

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Taphonomic damage of molluscan shells in the Nile Delta under natural and anthropogenic sources of environmental variability

Journal of African Earth Sciences, Journal Year: 2023, Volume and Issue: 210, P. 105159 - 105159

Published: Dec. 17, 2023

Language: Английский

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VERTEBRATE FOSSIL PERMINERALIZATION IN A SEQUENCE STRATIGRAPHIC CONTEXT: CAPSULES OF EARLY DIAGENESIS FROM SHALLOW-MARINE SILICICLASTICS (EOCENE, EGYPT)

Palaios, Journal Year: 2024, Volume and Issue: 39(8), P. 243 - 263

Published: Aug. 17, 2024

Abstract Understanding the drivers of vertebrate fossil preservation is important for paleontologists who rely on well-preserved fossils to study biological or ecological context fauna they represent. Differences in limit ability compare change across time. Bones, however, can contain clues their preservational history: natural voids skeletal remains are potential sites mineral precipitation during early and late diagenesis, reactive bioapatite provides chemical physical signals post-mortem environment. The sensitivity both infilling minerals taphonomic alteration environment has yet be tested record. Bones associated with discontinuity surfaces such as hiatal flooding erosional sequence boundaries should face prolonged exposure at sediment-water interface and/or within surface mixed layer, increasing opportunity modification by processes geochemically disparate (redox) conditions, compared bones from facies aggradational intervals, where burial most likely rapid immediately permanent. µXRF thin-section-based petrographic analysis marine mammal famously fossiliferous Eocene siliciclastics Wadi al-Hitan, Egypt, reveal strong variation stratigraphic position: found along boundary show Fe-oxide linings evidence desiccation subaerial exposure, distinct other settings; a bone maximum uniquely lacks calcite but brecciated cancellous bone; systems tracts variable extent infill microfacies consistent exclusively subaqueous specifically shallow deposition. Early diagenetic signatures were preserved despite many specimens being strongly fractured infilled gypsum precipitated weathering. abundant pore space thus acted time-capsules retaining authigenic microtaphonomic features linked original (Eocene) depositional context.

Language: Английский

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Pyrite-lined shells as indicators of inefficient bioirrigation in the Holocene–Anthropocene stratigraphic record

Biogeosciences, Journal Year: 2021, Volume and Issue: 18(22), P. 5929 - 5965

Published: Nov. 22, 2021

Abstract. Although the depth of bioturbation can be estimated on basis ichnofabric, timescale sediment mixing (reworking) and irrigation (ventilation) by burrowers that affects carbonate preservation biogeochemical cycles is difficult to estimate in stratigraphic record. However, pyrite linings interior shells a signature slow shallow irrigation. They indicate molluscs initially inhabiting oxic pockets were immediately permanently sequestered reduced, iron-rich microenvironments within mixed layer. Molluscan biomass-stimulated sulfate reduction precipitation was confined location decay under such conditions. A high abundance pyrite-lined record thus diagnostic limited exposure organic tissues O2 even when seafloor inhabited abundant infauna disrupting age-homogenizing sedimentary fabric as present-day northern Adriatic Sea. Here, we reconstruct this sequestration pathway characterized (1) assessing postmortem ages shallow-infaunal hypoxia-tolerant bivalve Varicorbula gibba cores (2) evaluating whether an independently documented decline mixing, driven frequency seasonal hypoxia during 20th century, affected First, at prodelta sites with sedimentation rate, framboids form rapidly upper 5–10 cm they already appear interiors younger than 10 years occur preferentially well-preserved articulated periostracum. Second, increments deposited early century contain < 20 % lined Po 30 %–40 Isonzo prodelta, whereas late possess 50 %–80 both locations. At low (< %–20 %). Surface sediments remained well deposit detritus feeders maintaining suboxic zone dissolved iron. The upcore increase indicates oxycline reduced bioirrigation rates declined century. We hypothesize permanent V. subsurface enabled recovery infaunal communities from hypoxic events, leading dominance surficial modifiers potential. presence very young valves uppermost zones layer rapid obrution episodic deposition not needed for transient background are (here, exceeding ∼ 0.1 yr−1) organisms die their living position sediment. Abundance per assemblage apparently well-mixed deep-time indicator inefficient bioirrigation. Fine-grained Sea since mid-20th potential formed layer, represent taphonomic diagenetic analogues skeletal assemblages linings.

Language: Английский

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Mediterranean onshore–offshore gradient in the composition and temporal turnover of benthic molluscs across the middle Piacenzian Warm Period

Geological Society London Special Publications, Journal Year: 2022, Volume and Issue: 529(1), P. 365 - 394

Published: Oct. 20, 2022

Abstract The mid-Piacenzian Warm Period (mPWP: 3.3–3.0 Ma) is the most recent geological analogue of ongoing climate change and has been subject considerable interest for numerical models system. To verify effect mPWP on diversity temporal turnover marine benthic communities, we evaluated changes in species-level abundance composition Mediterranean Pliocene molluscs prior, during after mPWP. onshore–offshore gradient species did not (and continued basically unchanged up to present day Sea), with dominant occupying same rank a given environment. During mPWP, evenness generally increased towards offshore environments. Within three time intervals, similarity greater environments, except when communities also exhibited dissimilarity. decreased again depth as global temperatures structure suggests that warming sea-level rise contributed expansion vegetated bottoms (onshore) shelly coralligenous (offshore). Although effects long term, its disproportionately affected deeper contrast colder regimes.

Language: Английский

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STRONTIUM ISOTOPE STRATIGRAPHY REVEALS 100 KY-SCALE CONDENSATION, BEVELING, AND INTERNAL SHINGLING OF TRANSGRESSIVE SHELL BEDS IN THE MARYLAND MIOCENE

Palaios, Journal Year: 2022, Volume and Issue: 37(10), P. 553 - 573

Published: Oct. 20, 2022

Abstract Condensed transgressive shell beds, rich in paleobiological information, are common the Phanerozoic stratigraphic record, but their interpretation is complicated by uncertain amount of time that each deposit represents. Miocene strata exposed Calvert Cliffs (Maryland, USA) known for a series regionally extensive, densely packed, meters-thick beds serve as global exemplars shallow-water condensation during marine transgression and onlap. Applying Sr isotope stratigraphy to calcitic scallops from base top oldest these (Shattuck Zone 10), we demonstrate its most fossiliferous part accumulated over interval 16.60–15.95 Ma, reflecting approximately 0.65 ±0.20 Myr skeletal accumulation within Climatic Optimum, with likely 0.15 Myr-scale averaging per firmground-bounded subunit. Both estimates an order magnitude longer than previous best based on radiocarbon-dated Holocene analogs. isotopes confirm subtle low-angle erosional beveling main body 10, truncating 0.3-Myr record updip sections, down-dip wedge less shelly sand entirely younger (by ∼ 0.5 Myr) interleaved body. This condensation, beveling, inter-shingling 10 quantified here sets precedent lateral vertical temporal variability condensed deposits, relevant paleobiologic other geohistorical analysis, justifies comparably complex fabrics upon similar physical features found elsewhere this very thin records.

Language: Английский

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