Stable Isotopic Investigation of Carbonate Samples Related to the Messinian Salinity Crisis from DSDP Leg 42A, Mediterranean Sea

McKenzie, Judith; Ricchiuto, T.

doi:10.2973/dsdp.proc.42-1.126-2.1978

Cited by 7 publications

(6 citation statements)

References 11 publications

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“…The occurrence of Lago-Mare biofacies at the eastern end-member of the Mediterranean transect south of Cyprus and the strongly negative isotopic signature of the ostracode shells confirm the nonmarine nature of the latest Messinian sediments laid down after the evaporitic episodes, as previously pointed out by Cita et al (1978) and McKenzie and Ricchiuto (1978). In the Eastern Mediterranean, the deep-sea nature of the earliest Zanclean sediments is also confirmed, as is the progressive repopulation by the benthic communities with deep bathyal Atlantic taxa first appearing ~200,000 years after the initial flooding (Wright, 1980;.…”

Section: Discussionsupporting

confidence: 56%

The Miocene/Pliocene boundary in the Eastern Mediterranean: results from Sites 967 and 969

Spezzaferri¹,

Cita²,

McKenzie³

1998

Proceedings of the Ocean Drilling Program

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Continuous sequences developed across the Miocene/Pliocene boundary were cored during Ocean Drilling Project (ODP) Leg 160 at Hole 967A, located on the base of the northern slope of the Eratosthenes Seamount, and at Hole 969B, some 700 km to the west of the previous location, on the inner plateau of the Mediterranean Ridge south of Crete. Multidisciplinary investigations, including quantitative and/or qualitative study of planktonic and benthic foraminifers and ostracodes and oxygen and carbon isotope analyses of these microfossils, provide new information on the paleoceanographic conditions during the latest Miocene (Messinian) and the re-establishment of deep marine conditions after the Messinian Salinity Crisis with the re-colonization of the Eastern Mediterranean Sea in the earliest Pliocene (Zanclean).At Hole 967A, Zanclean pelagic oozes and/or hemipelagic marls overlie an upper Messinian brecciated carbonate sequence. At this site, the identification of the Miocene/Pliocene boundary between 119.1 and 119.4 mbsf, coincides with the lower boundary of the lithostratigraphic Unit II, where there is a shift from a high content of inorganic and non-marine calcite to a high content of biogenic calcite typical of a marine pelagic ooze. The presence of Cyprideis pannonica associated upward with Paratethyan ostracodes reveals that the upper Messinian sequence is complete. The stable isotope composition of C. pannonica indicates that this crustacean lived in a Lago Mare environment characterized by brackish water, distinctly different from the marine environment. At Hole 969B, the identification of the Miocene/Pliocene boundary coincides with a marked lithologic change between 97.1 and 97.2 mbsf. The marine sediments directly overlie latest Messinian Lago Mare facies deposits comprising dark gray clay. The presence of planktonic foraminifers associated with brackish water ostracodes in Hole 967A, and with the gray clay in Hole 969B, may indicate temporary incursions of Atlantic water into a fully Lago Mare environment. This interpretation is also supported by the trends in the isotopic composition of the ostracodes and planktonic foraminifers.After the Messinian Salinity Crisis, benthic foraminifers slowly repopulated the Eastern Mediterranean seafloor during the Sphaeroidinellopsis acme event (Biozone MPl1). The gradual ingression of typical deep Atlantic benthic foraminifers, Parrelloides bradyi and P. robertsonianus, and the presence of Globorotalia menardii (planktonic foraminifer) coincident with the boundary between the biozones MPl1 and MPl2 indicate that an efficient connection between the Atlantic Ocean and the Eastern Mediterranean Sea was re-established in this interval.

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Section: Discussionsupporting

confidence: 56%

The Miocene/Pliocene boundary in the Eastern Mediterranean: results from Sites 967 and 969

Spezzaferri¹,

Cita²,

McKenzie³

1998

Proceedings of the Ocean Drilling Program

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“…, 1978a). Stable isotopes confirmed the importance of rain, river and groundwater in diluting residual brines (McKenzie & Ricchiuto, 1978; Pierre & Fontes, 1978; Ricchiuto & McKenzie, 1978).…”

Section: The Next Drilling Expedition In 1975mentioning

confidence: 88%

Decoding the Mediterranean salinity crisis

2008

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This historical narrative traces the steps to unravel, over a span of 40 years, an extraordinary event in which 5% of the dissolved salt of the oceans of the world was extracted in a fraction of a million years to form a deposit more than 1 million km 3 in volume. A buried abyssal salt layer was identified with reflection profiling and sampled during the Deep Sea Drilling Project, Leg 13. The dolomite, gypsum, anhydrite and halite in the drill cores paint a surprising picture of a Mediterranean desert lying more than 3 km below the Atlantic Ocean with brine pools that shrank and expanded by the evaporative power of the sun. The desert drowned suddenly when the Gibraltar barrier gave way. The explanation of 'deep-basin, shallow-water' desiccation and the notion of a catastrophic Zanclean flood had a mixed reception. However, the hypothesis became broadly accepted following subsequent drilling expeditions. Nevertheless, as experts examined the evaporate facies and sequences of equivalent age in the terrestrial outcrops, weaknesses appeared in the concept of repeated flooding and drying to account for the magnitude of the deposits. The 'Rosetta Stone', used to decipher conflicting interpretations, turns out not to be the deposits but the erosion surfaces that enclose them. These surfaces and their detritus -formed in response to the drop in base level during evaporative drawdown -extend to the basin floor. Evaporative drawdown began halfway through the salinity crisis when influx from the Atlantic no longer kept up with evaporation. Prior to that time, a million years passed as a sea of brine concentrated towards halite precipitation. During the later part of this interval, more than 14 cyclic beds of gypsum accumulated along shallow margins, modulated by orbital forcing. The thick salt on the deep seabed precipitated in just the next few cycles when drawdown commenced and the brine volume shrank. Upon closure of the Atlantic spillway, the remnants of the briny sea transformed into salt pans and endorheic lakes fed from watersheds of Eurasia and Africa. The revised model of evaporative concentration now has shallow-margin, shallow-water and deep-basin, deep-water precursors to desiccation.

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“…In this case, fresh water with enriched isotopic composition coming from destabilization of ''ancient'' gas-hydrates (Figs. 7, 8;Maekawa and Imai 2000;Conti et al 2007) For the Salsomaggiore brines, in order to check their possible provenance from the Late Triassic formation, or its origin by mixing with waters coming from this formation, oxygen and sulfur isotope of sulfate molecula were compared with Messinian sulfate from the Mediterrranean area (Longinelli 1979;Ricchiuto and McKenzie 1978;Pierre and Rouchy 1990;Lu and Meyers 2003), dissolved sulfate of Po Basin groundwaters interacting with Messinian sulfate (Olivero et al 1987) and Triassic sulfate from Italian Eastern Alps (Longinelli and Flora 2007) and Northern Apennines (Boschetti et al 2010;Fig. 9).…”

Section: Oxygen and Hydrogen Isotope Composition Of Watermentioning

confidence: 99%

Salt Waters of the Northern Apennine Foredeep Basin (Italy): Origin and Evolution

et al. 2010

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The salt waters from the Emilia-Romagna sector of the Northern Apennine Foredeep have been investigated using major and trace element and stable isotope (d 2 H, d 18 O, d 37 Cl, d 81 Br and 87 Sr/ 86 Sr ratio). Ca, Mg, Na, K, Sr, Li, B, I, Br and SO 4 vs. Cl diagrams suggest the subaerial evaporation of seawater beyond gypsum and before halite precipitation as primary process to explain the brine's salinity, whereas saline to brackish waters were formed by mixing of evaporated seawater and water of meteoric origin. A diagenetic end-member may be a third component for mud volcanoes and some brackish waters. Salinization by dissolution of (Triassic) evaporites has been detected only in samples from the Tuscan side of the Apennines and/or interacting with the Tuscan Nappe. In comparison with the seawater evaporation path, Ca-Sr enrichment and Na-K-Mg depletion of the foredeep waters reveal the presence of secondary processes such as dolomitization-chloritization, zeolitization-albitization and illitization. Sulfate concentration, formerly buffered by gypsum-anhydrite deposition, is heavily lowered by bacterial and locally by thermochemical reduction during burial diagenesis. From an isotopic point of view, data of the water molecule confirm mixing between seawater and meteoric endmembers. Local 18 O-shift up to ?11% at Salsomaggiore is related to water-rock interaction at high temperature (&150°C) as confirmed by chemical (Mg, Li, Ca distribution) and isotopic (SO 4 -H 2 O) geothermometers. 37 Cl/ 35 Cl and 81 Br/ 79 Br ratios corroborate the Electronic supplementary material The online version of this article (marine origin of the brines and evidence the diffusion of halogens from the deepest and most saline aquifers toward the surface. The 87 Sr/ 86 Sr ratio suggests a Miocene origin of Sr and rule out the hypothesis of a Triassic provenance of the dissolved components for the analyzed waters issuing from the Emilia-Romagna sector of the foredeep. Waters issuing from the Tuscan side of the Apennines and from the Marche sector of the foredeep show higher 87 Sr/ 86 Sr ratios because of the interaction with siliciclastic rocks.

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Stable Isotopic Investigation of Carbonate Samples Related to the Messinian Salinity Crisis from DSDP Leg 42A, Mediterranean Sea

Cited by 7 publications

References 11 publications

The Miocene/Pliocene boundary in the Eastern Mediterranean: results from Sites 967 and 969

The Miocene/Pliocene boundary in the Eastern Mediterranean: results from Sites 967 and 969

Decoding the Mediterranean salinity crisis

Salt Waters of the Northern Apennine Foredeep Basin (Italy): Origin and Evolution

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