Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils (original) (raw)
Related papers
2013
Fossil shark remains occur in both marine and nonmarine Late Palaeozoic deposits, therefore their palaeoecology is controversial. The oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth, scales and spines predominantly of hybodontid (Lissodus) and xenacanthiform (Orthacanthus, Xenacanthus, Bohemiacanthus, Triodus) sharks from various Late Carboniferous (Moscovian) to Early Permian (Artinskian) basins of Europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa. The δ 18 O P values of the different shark teeth range from 11.7 to 20.2‰ within the different basins with mean values of 16.9 ± 0.5‰ for the Bohemian Massif, 16.2 ± 0.8‰ for eastern Germany, 18.2 ± 1.0‰ for southwestern Germany, 18.5 ± 0.7‰ for southern-central Spain, 17.6 ± 0.4‰ for Sardinia, and 16.6 ± 0.5‰ VSMOW for the French Massif Central. The tooth δ 18 O P values from the basins are mostly depleted by 1-5‰ relative to those of shark teeth from contemporaneous marine settings. Oxygen isotope signatures of co-occurring taxa do not show systematic differences excluding habitat effects for different shark groups. However, distinctly higher δ 18 O P values from Puertollano and Saar-Nahe can be attributed to significant evaporative enrichment in 18 O of the ambient water in the ancient lacustrine environments due to a warm and dry climate and sufficient residence time in the basins. The strontium isotopic composition of the teeth varies between 0.70824 and 0.71216 with a mean value of 0.71031. These 87 Sr/ 86 Sr ratios are always more radiogenic in comparison to the 87 Sr/ 86 Sr record of seawater of their stratigraphic age. Overall, the investigated tooth samples yield low δ 18 O P and high 87 Sr/ 86 Sr values deviating from bioapatite values expected for contemporaneous marine vertebrates and typical for freshwater settings. This indicates a fully freshwater adapted lifestyle for a variety of fossil shark taxa in Late Palaeozoic European basins.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2012
Fossil shark remains occur in both marine and nonmarine Late Palaeozoic deposits, therefore their palaeoecology is controversial. The oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth, scales and spines predominantly of hybodontid (Lissodus) and xenacanthiform (Orthacanthus, Xenacanthus, Bohemiacanthus, Triodus) sharks from various Late Carboniferous (Moscovian) to Early Permian (Artinskian) basins of Europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa. The δ 18 O P values of the different shark teeth range from 11.7 to 20.2‰ within the different basins with mean values of 16.9 ± 0.5‰ for the Bohemian Massif, 16.2 ± 0.8‰ for eastern Germany, 18.2 ± 1.0‰ for southwestern Germany, 18.5 ± 0.7‰ for southern-central Spain, 17.6 ± 0.4‰ for Sardinia, and 16.6 ± 0.5‰ VSMOW for the French Massif Central. The tooth δ 18 O P values from the basins are mostly depleted by 1-5‰ relative to those of shark teeth from contemporaneous marine settings. Oxygen isotope signatures of co-occurring taxa do not show systematic differences excluding habitat effects for different shark groups. However, distinctly higher δ 18 O P values from Puertollano and Saar-Nahe can be attributed to significant evaporative enrichment in 18 O of the ambient water in the ancient lacustrine environments due to a warm and dry climate and sufficient residence time in the basins. The strontium isotopic composition of the teeth varies between 0.70824 and 0.71216 with a mean value of 0.71031. These 87 Sr/ 86 Sr ratios are always more radiogenic in comparison to the 87 Sr/ 86 Sr record of seawater of their stratigraphic age. Overall, the investigated tooth samples yield low δ 18 O P and high 87 Sr/ 86 Sr values deviating from bioapatite values expected for contemporaneous marine vertebrates and typical for freshwater settings. This indicates a fully freshwater adapted lifestyle for a variety of fossil shark taxa in Late Palaeozoic European basins.
Palaeogeography Palaeoclimatology Palaeoecology, 1998
The Upper Marine Molasse sediments of southern Germany were deposited during the Early to Middle Miocene, a period of significant change for the global Miocene palaeoceanography, palaeoclimate, and the regional palaeogeography because of the ongoing Alpine–Himalayan orogeny. To address the influence of the Alpine uplift on climate and oceanography of the northern Alpine molasse basin, a combined O-, Sr-, and Nd-isotope study was undertaken on fossil teeth from sharks (Synodontaspis sp., Galeocerdo cf. aduncus, Chaenogaleus sp.), and button-like teeth from the bony fish of the Upper Marine Molasse (Chrysophrys molassica). Average δ18O values for hydroxyapatite of teeth from two sites are 20.3‰ (1σ=0.6) and 21.2‰ (1σ=0.5), while their average 87Sr/86Sr and 143Nd/144Nd ratios are 0.70850 (±0.00001, 2σ) and 0.70882 (±0.00003, 2σ), and 0.51220, and 0.51223 (both at ±0.00001, 2σ), respectively. By comparison to the Sr-evolution curve for the global ocean, the Sr-isotope compositions suggest ages of about 22 and 17 Ma for the teeth. These ages are in good agreement with the depositional ages, which suggests open marine conditions. Open marine conditions are also compatible with (1) lower average δ18O values and 87Sr/86Sr ratios for the one site compared to higher δ18O values and higher 87Sr/86Sr ratios for the other site, (2) estimates for seawater temperatures which are similar to other estimates from deposits of similar latitude and age, (3) a comparison of seawater temperatures with average ambient air temperature estimates deduced from continental palaeoclimate indicators. Nd-isotope compositions are compatible with an influence of the North Atlantic on the Paratethys. Assuming constant salinity and seawater oxygen isotope composition, a 4°C cooling can be inferred from average δ18O values of the teeth between 22 and 17 Ma. This is similar to trends observed for foraminiferal records from the Mediterranean Tethys, but different from foraminiferal and molluscan records of the North Atlantic and the North Sea during this period, and allows for the possibility that the Alpine orogeny had an influence on the regional, circum-Alpine climate.
Paleoceanography, 1988
We improved upper Eocene to Oligocene deepsea chronostratigraphic control by integrating isotope (87Sr/StSr, •80, •3C) stratigraphy and magnetostratigraphy. Most previous attempts to establish the timing of isotope fluctuations have relied upon biostratigraphic age estimates which have uncertainties of 0.5 to over 4.0 m.y. Deep Sea Drilling Project (DSDP) Site 522 contains the best available upper Eocene to Oligocene magnetostratigraphic record which allows first-order correlations of isotope records (87Sr/86Sr, 8•O, 193C) to the Geomagnetic Polarity Time Scale (GPTS). Empirical calibrations between the 87Sr/86Sr of foraminifera and magnetochronology at Site 522 allow more precise correlation of "unknown" samples with the GPTS. For example, shallow water and high-latitude sections may be tied into the deep-sea record. Sr-isotope stratigraphic resolution for the latest Eocene to Oligocene is approximately 2 m.y. BACKGROUND The advent of the Deep Sea Drilling Project and its successor the Ocean Drilling Program (ODP) provided recovery of relatively complete deep-sea sedimentary sequences. Since the pioneering work of Shackleton and Kennett [1975] and Savin et al. [ 1975], oxygen and carbon isotope measurements on these deep-sea sections have become routine for paleoceanographic and stratigraphic studies (see Miller et al., [1987] for a synthesis of Tertiary oxygen isotopes). Stratigraphic correlations using •980 and •93C records rely upon matching patterns of change, and therefore are usually not unique. More recently, studies by Burke etal. [1982], DePaolo and Ingram [1985], and Hess et al. [1986] have shown the potential for using the record of 87Sr/86Sr preserved in marine carbonates as a stratigraphic tool. The Sr-isotope ratio in seawater is believed to be uniform at a given time, since the residence time is much longer than oceanic mixing times [Broecker and Peng, 1982]. A large increase in the 87Sr/StSr record (-0.001300) measured in marine carbonates occurred from the late Eocene to Recent [Burke etal., 1982;
Strontium isotopic variations in Jurassic and Cretaceous seawater
… et Cosmochimica Acta, 1994
A high-resolution seawater strontium isotope curve has been generated through the analysis of well-dated and well-preserved belemnites and oysters from the Middle and Upper Jurassic and the Lower Cretaceous of Great Britain. Analysis of Fe and Mn concentrations in these fossils has yielded criteria for eliminating samples that are diagenetically altered. The strontium isotope curve remains relatively flat through the Aalenian and early Bajocian, rapidly descends through the late Bajocian and Bathonian, and reaches a minimum in the Callovian and Oxfordian. It then begins a rapid increase in the Kimmeridgian and Portlandian that continues through much of the early Cretaceous. The curve levels off in the Barremian, suddenly dips downwards in the Aptian, and recovers gradually through the Albian. The strontium isotopic variations are sufficiently large and the data are presented with sufficient stratigraphic detail to allow precise correlation to the classic ammonite zones and lithologic sections of Great Britain using the techniques of strontium isotope stratigraphy.
d18OP values and 87Sr/86Sr ratios were determined on disarticulated xenacanthiform, hybodontid and ctenacanthid shark tooth material from several Early Permian (Sakmarian–Kungurian) continental bone beds of northern Texas and southern Oklahoma as well as from the marine Middle Permian (Roadian) of northern Arizona. The d18OP values derived from the teeth of bone beds are in the range of 17.6–23.5‰ VSMOW, and are mostly depleted in 18O by 0.5–5‰relative to proposed coeval marine d18OP values. This indicates an adaptation to freshwater habitats on the Early Permian coastal plain by several sharks. Distinctly higher d18OP values from two bone beds are attributed to significant evaporative enrichment in 18O in flood plain ponds. 87Sr/86Sr ratios of around 0.71077 are notably more radiogenic than 87Sr/86Sr of contemporaneous seawater. In contrast, the isotopic composition of teeth from the marine Kaibab Formation is characterised by low d18OP values in the range of 13.4–15.6‰ VSMOW while 87Sr/86Sr ratios of around 0.70821 are closer to the Roadian seawater value. The distinctly depleted d18OP values cannot be readily explained by fluvially affected freshening in a nearshore marine environment, so a diagenetic alteration of the Kaibab material seems to be more likely, excluding it from further interpretation.
2016
Marine vertebrate fossils from late Cretaceous–early Paleogene shallow marine phosphorites of Morocco were investigated for their trace element compositions and neodymium isotopic ratios in order to constrain marine and depositional conditions. The various analyzed fossils are separated into two groups with different geochemical compositions: (1) shark tooth enameloid with generally lower Cu, Ba, rare earth elements (REEs) and U, and higher Na, Zn and Sr concentrations than (2) dentine, bone, and coprolites. These differences are related to the originally different structures of these fossils. All the fossils revealed very similar shale-normalized REE patterns, with negative Ce anomaly and heavy REE enrichment mimicking the REE pattern of modern oxic-seawater. The results therefore suggest REE uptake by the fossils from an early diagenetic pore fluid that was dominated by seawater. Importantly, the Ce anomaly does not vary among the different types of fossil remains and the values are very similar in a given layer. Moreover, a step-wise shift towards lower Ce/Ce* values from older to younger beds is apparent. Nd isotope analyses across the phosphorite succession yielded minor variation with an average εNd(t) value of−6.2±0.4 (n=12) indicating no major changes in the REE source during the studied interval. The relatively radiogenic values reflect Tethyan connection and/or important contribution of a mafic Nd source from weathering in the region. The age-related trend in the Ce anomaly is interpreted to be due to changes in redox and/or pH conditions of the upwelling seawater on the shallow shelf areas. The driving force of these changes was probably an extended global oceanic circulation, especially enhanced connection and water exchange between the North and South Atlantic.
Mineralogia, 2011
We report the results of high-precision (±0.05‰) oxygen isotope analysis of phosphates in 6 teeth of fossil sharks from the Mangyshlak peninsula. This precision was achieved by the offline preparation of CO2 which was then analyzed on a dual-inlet and triple-collector IRMS. The teeth samples were separated from Middle-and Late Bartonian sediments cropping out in two locations, Usak and Kuilus. Seawater temperatures calculated from the 18 O data vary from 23-41 o C. However, these temperatures are probably overestimated due to freshwater inflow. The data point at higher temperature in the Late Bartonian than in the Middle Bartonian and suggest differences in the depth habitats of the shark species studied.
Frontiers in Ecology and Evolution, 2020
Skeletal remains in archaeological strata are often assumed to be of similar ages. Here we show that combined Sr and O isotope analyses can serve as a powerful tool for assessing fish provenance and even for identifying fossil fish teeth in archaeological contexts. For this purpose, we established a reference Sr and O isotope dataset of extant fish teeth from major water bodies in the Southern Levant. Fossil shark teeth were identified within Iron Age cultural layers dating to 8–9th century BCE in the City of David, Jerusalem, although the reason for their presence remains unclear. Their enameloid 87Sr/86Sr and δ18OPO4 values [0.7075 ± 0.0001 (1 SD, n = 7) and 19.6 ± 0.9‰ (1 SD, n = 6), respectively], are both much lower than values typical for modern marine sharks from the Mediterranean Sea [0.7092 and 22.5–24.6‰ (n = 2), respectively]. The sharks’ 87Sr/86Sr are also lower than those of rain- and groundwater as well as the main soil types in central Israel (≥0.7079). This indicates...