Strontium, .DELTA.18O and .DELTA.13C as palaeo-indicators of unconformities: Case of the Aleg and Abiod formations (Upper Cretaceous) in the Miskar Field, Southeastern Tunisia

Mabrouk, Amina; Belayouni, Habib; Jarvis, Ian; Moody, Richard

doi:10.2343/geochemj.40.405

Cited by 20 publications

(3 citation statements)

References 54 publications

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“…Nevertheless, Late Cretaceous marine carbonates are abundant in the wider region of the Gafsa Basin (e.g., Abdallah et al 1995Abdallah et al , 2000Mabrouk et al 2006;Lazzez et al 2008), and these sediments are known to have low Sr isotope ratios (McArthur et al 2001). Clear paleontological evidence for active re-working of such rocks is documented by the presence of large amount of upper Cretaceous, calcareous nannofossils that occur in many intercalated marl beds of the Chouabine Formation (e.g., Bolle et al 1999).…”

Section: Strontium Isotope Ratio As Paleoenvironmental Proxymentioning

confidence: 99%

Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils

Kocsis

Ounis

Chaabani

et al. 2012

Int J Earth Sci (Geol Rundsch)

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Fossil shark teeth and coprolites from three major phosphorite occurrences in the Gafsa Basin (southwestern Tunisia) were investigated for their geochemical compositions to improve local stratigraphy and to better assess paleoenvironmental conditions. 87 Sr/ 86 Sr isotope ratios of shark teeth from the Early Maastrichtian El Haria Formation and from the Early Eocene Métlaoui s.s. Formation yielded Sr isotope ages of 68 ± 1 and 47.9 ± 1.3 Ma, respectively, which accord with the expected stratigraphic positions of these sediments. Conversely, shark teeth from the Paleocene-Eocene Chouabine Formation have large variation in Sr isotope ratios even within individual layers. After statistical treatment and then elimination of certain outlier samples, three age-models are proposed and discussed. The most reasonable solution includes three subsequent Sr ages of 61.8 ± 2.2 Ma, 57.2 ± 1.8 and 54.6 ± 1.6 for layer IX, layers VIII-V and layers IV-0, respectively. Three scenarios are discussed for explanation of the presence of the outliers: (1) diagenesis, (2) re-working and (3) locally controlled seawater Sr isotope ratio. The most plausible account for the higher 87 Sr/ 86 Sr ratios relative to the global ocean in some fossils is enhanced intrabasinal re-working due to low sea level. Conversely, the sample with lower 87 Sr/ 86 Sr than the global seawater may link to diagenesis or to seawater influenced by weathering of Late Cretaceous marine carbonates, which latter is supported by model calculation as well. The e Nd values of these fossils are very similar to those reported for Paleogene and Late Cretaceous Tethyan seawater and are compatible with the above interpretations. The relatively low oxygen isotope values in shark teeth from the topmost phosphate bed of the Chouabine Formation, together with the Sr isotope results, point toward recovering better connections with the open sea. These d 18 O data reflect elevated ambient temperature, which may link to the Early Eocene Climatic Optimum.

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Section: Strontium Isotope Ratio As Paleoenvironmental Proxymentioning

confidence: 99%

Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils

Kocsis

Ounis

Chaabani

et al. 2012

Int J Earth Sci (Geol Rundsch)

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“…A sea‐level fluctuation in chemostratigraphy is noted in this tract, where an observed increase Mn content and associated with decrease in Sr/Ba ratio. Towards the top, a depletion in most elements has been documented elsewhere as being a consequence of burial diagenesis (Mabrouk et al, ).…”

Section: Discussionmentioning

confidence: 88%

“…TST1 (samples 1–5): It consists of lower phosphorites beds of the Sultani Phosphorite Member, which is being intercalated with bioclastic siliceous limestone/mudstone and displays a relatively high TOC contents. A marked global marine transgression produced frequent reworked granular phosphorite deposits with Thalassinoides burrows, which contain high amount of Sr, Ba, and B that accumulated in transgressive lag deposits during low sea level (Mabrouk, Belayouni, Jarvis, & Moody, ). An observed decrease in Sr, Ba, and B towards the upper part of the TST1 in the siliceous limestone is associated with a relative increase of TOC, Mo, Pb, Cu, Zn, Ag.…”

Section: Discussionmentioning

confidence: 99%

Geochemistry and stable isotopes of the upper Campanian–lower Maastrichtian phosphorite‐bearing sequence, Central Jordan: Implications for their age, origin, and diagenesis

et al. 2019

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Three major lithofacies have been described in Lajjun area, central Jordan, including the phosphorite and intercalated limestone of the Al-Hisa Phosphorite Formation, as well as the Muwaqqar Chalk Marl Formation. 87 Sr/ 86 Sr isotopic data indicate a late Campanian age for the Al-Hisa Phosphorite Formation, whereas the overlying chalk of the Muwaqqar Formation contains the lowest Maastrichtian planktic foraminiferal zone of Rugoglobigerina hexacamerata (CF8b). The phosphorites are of reworked origin as inferred from the homogeneous texture with lack of any concentric structure in the phosphatic pellets and the presence of bone fragments inside the phosphatic pellets, which are filled with phosphatic mud similar to the matrix of phosphatic pellet. They still reflect the original seawater rare-earth pattern, as indicated from the similarity in their rare-earth element (REE) concentration and patterns with seawater. Positive correlations between P 2 O 5 and Fe 2 O 3 , TiO 2 and K 2 O, relatively high rare-earth contents, and similarity in (Nd/Yb) SN ratio to the modern shallow seawater suggest a continental marginal depositional environment for the limestone and chalk facies. δ 13 C values are lower and more variable compared with the estimated global range of upper Campanian-lowerMaastrichtian δ 13 C values in shelf and oceanic basins. This indicates a diagenetic effect on the δ 13 C isotopes and suggests that a significant proportion of carbonate ions could have been resulted from the organic carbon oxidation. Three third-order depositional sequences matching with the global and regional sea-level patterns are identified in the studied section based on vertical facies changes. The basal transgressive surface of each sequence is constantly characterized by a phosphatic horizon.

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Late Cretaceous–Paleocene Depsits

Shaltami

Fares

Errishi

et al. 2020

Isotope Geochronology of the Exposed Rocks in the Cyrenaica Basin, NE Libya

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Strontium, .DELTA.18O and .DELTA.13C as palaeo-indicators of unconformities: Case of the Aleg and Abiod formations (Upper Cretaceous) in the Miskar Field, Southeastern Tunisia

Cited by 20 publications

References 54 publications

Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils

Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils

Geochemistry and stable isotopes of the upper Campanian–lower Maastrichtian phosphorite‐bearing sequence, Central Jordan: Implications for their age, origin, and diagenesis

Late Cretaceous–Paleocene Depsits

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