Marine carbonates

Illing, L. V.

doi:10.1016/0031-0182(76)90043-2

Cited by 44 publications

(80 citation statements)

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“…–Steuber & Veizer, 2002) and also generally lower than those of modern marine calcites (including biota and cements – e.g. Milliman, 1974), thus suggesting some mineral stabilization during burial. High‐resolution sampling of core segment S1‐101 reveals rather stable Sr values of c .…”

Section: Discussionmentioning

confidence: 95%

The aftermath of the Carnian carbonate platform demise: a basinal perspective (Dolomites, Southern Alps)

Keim¹,

Spötl²,

Brandner³

2006

Sedimentology

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In the Dolomites of northernmost Italy the carbonate-platform growth came to a standstill late in the Early Carnian (Late Triassic). The response to this shutdown of shallow-water carbonate production in the interplatform basins is largely unknown because erosion has removed most of the soft basinal sediments, giving rise to today's scenic landscape of the Dolomites. Mapping in the central part of the Dolomites and newly available core material has recently revealed a wellpreserved succession of basinal rocks within the Heiligkreuz Hospiz Basin (ital. Ospizio di Santa Croce Basin). In this paper, the regional depositional nature of arrested carbonate platform production is reconstructed by tracing its sedimentological record across the slope and into the basin. The uppermost St. Cassian Formation, the time-equivalent basinal rocks to the prograding carbonate platforms, is overlain by the Heiligkreuz Formation, whose basal succession was deposited in a restricted and oxygen-depleted environment immediately post-dating the platform demise. The succession consists mainly of mudrocks, marlstones, and peloidal packstones, with abundant low-diversity ostracod and pelecypod fauna and early diagenetic dolomite. C and O isotope values of the basal Heiligkreuz Formation, post-dating platform demise, average + 2AE4 and ) 2AE4&, respectively, and largely overlap the isotopic composition of St. Cassian carbonates. A shift toward slightly lower d 13 C values in the Heiligkreuz Formation may reflect incorporation of isotopically depleted C released during bacterial sulphate reduction in the Heiligkreuz sediments. Sedimentological, palaeobiological and geochemical indices suggest that nearnormal marine conditions persisted long after the shutdown of shallow water carbonate-platform growth, although there are clear indications of severely reduced oxygen levels in the restricted Heiligkreuz Hospiz interplatform basin. The Early Carnian platform demise induced a distinct switch in the locus of carbonate production from the shallow-water platform and slope to the basin floor and a decrease in the availability of dissolved oxygen in the basinal waters. It is inferred that anoxia extended at least temporarily to the top of the carbonate slope, as indicated by the onlap of normal-marine mounds by dark marlstones of the basal Heiligkreuz Formation.

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Section: Discussionmentioning

confidence: 95%

The aftermath of the Carnian carbonate platform demise: a basinal perspective (Dolomites, Southern Alps)

Keim¹,

Spötl²,

Brandner³

2006

Sedimentology

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“…3 is that of marine crustaceans. As a group, crustaceans which include barnacles ( 1 .O to 1.6 mol% MgC03; PILKEY and HARRIS, 1966) ostracodes (0.8 to 10.8 mol% MgC03; CADOT et al, 1972; BURKE and BISCHOEE, 1989) and decapods (2.0 to 13.2 mol% MgC03; MILLIMAN, 1974), have si~ifi~ntly higher Sr contents than other biotic marine calcite. LMC barnacles contain from 2300 to 2600 ppm Sr ( P~LKEY and HARRIS& 1966).…”

Section: Marine Crustaceans: An Exception To the Rule?mentioning

confidence: 99%

ratios of modern marine calcite: Empirical indicators of ocean chemistry and precipitation rate

Carpenter

Lohmann

1992

Geochimica et Cosmochimica Acta

220

121

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Holocene biotic and abiotic marine calcite have a similar range of Mg contents (0 to 22 and 4 to 2 1 mol% MgC03, respectively), yet biotic calcite has Sr*+ concentrations that are consistently 1250 ppm higher than those of abiotic calcite. As in laboratory experiments, a positive linear relation is observed between Dsr and calcite Mg content. This produces two distinct linear trends on a plot of Sr2+ vs. Mg2+ concentrations. Principal axes of variation for both trends have similar slopes, yet distinctly different Sr'+ concentration intercepts. (Biotic: y = 0.024x + 1298, r2 = 0.70; Abiotic: y = 0.027x + 47, r2 = 0.77). The similar slopes of these trends reflect the constancy of Mg/Ca and Sr/Ca ratios of modem seawater. Equations describing the dependence of Ds* on calcite Mg content are derived from both trends (Biotic: Ds,,, = 3.16 X lo-@' (ppm Mg) + 0.169; Abiotic: Ds* = 3.52 X 10e6 (ppm Mg) + 0.0062). Characterization of Sr-Mg trends for Holocene materials allows comparison with analogous trends from ancient samples to estimate relative changes in seawater Mg/Ca and Sr/Ca ratios. The relatively high Sr contents of biotic calcite result from rapid p~~pi~tion rates associated with shell accretion in marine organisms. Calcites precipitated from seawater in laboratory experiments have Dsr values that are similar to those of biotic marine calcite, suggesting that both precipitate at approximately the same rate. Our estimates of surface area-normalized precipitation rates in planktonic and benthonic foraminifera are comparable to those of seeded, pH-stat experiments. We conclude that the Dsl values for biotic and experimental marine calcite are kinetically controlled, whereas the lower precipitation rates of abiotic marine calcite yield Dsl values that approximate equilibrium conditions. Experimentally derived equations describing the relation between Dsr and calcite precipitation rate indicate that the offset in Sr content between biotic and abiotic calcite is the result of abiotic precipitation rates that are two to five orders of magnitude lower than those of biotic precipitates. However, observations of naturally occurring marine cements suggest that the five-order-of-magnitude offset best represents natural system processes.

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“…Each sample of fine sediment was dried at 60°C, ground for < 1 min by hand in an agate mortar, sieved to obtain an agglomerate of <63-/an particles, and packed with a spatula into an aluminum sample holder. The effects of particle size on the semiquantitative XRD estimate and the effects of mineralogy change by grinding are minimized through these procedures (Milliman, 1974). Each sample was analyzed with a Phillips-Norelco Model 12045 (60 cycles) diffractometer with Dapple Systems Controller Thetaplus® Software.…”

Section: Carbonate Mineralogy Of the Fine Fractionmentioning

confidence: 99%

Pliocene-Pleistocene Aragonite Cyclic Variations in Holes 714A and 716B (the Maldives) Compared with Hole 633A (the Bahamas): Records of Climate-Induced CaCO3 Preservation at Intermediate Water Depths

Droxler¹,

Haddad²,

Mucciarone³

et al. 1990

Proceedings of the Ocean Drilling Program, 115 Scientific Results

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Ocean Drilling Program (ODP) Leg 115 post-cruise research was focused on two Maldives sites, more precisely on the top 108 m of Hole 716B (water depth, 540 m), equivalent to the past 3.5 m.y., and the top 19.5 m of Hole 714A (water depth, 2195 m), equivalent to the past 0.55 m.y. These sediments consist of mostly unaltered and undisturbed, turbidite-free, periplatform ooze. Results of our research are compared with existing data on Hole 633A (water depth, 1681 m), drilled in the Bahamas during ODP Leg 101, using age/depth models built on the basis of oxygen isotope, nannofossil, and magnetic stratigraphies. Climate-induced, long-term (roughly 0.5 m.y.) aragonite cycles, superposed on short-term (roughly 0.04 and 0.1 m.y.) aragonite cycles, have been established at least during the past 2.0 m.y., in the Maldives and the Bahamas. Our most interesting result is the clear correlation among the aragonite long-term cycles in the Maldives and the Bahamas and the carbonate-preservation, long-term cycles from the open Pacific, Indian, and North Atlantic oceans. The mid-Brunhes dissolution interval, corresponding to the youngest preservation minima of the carbonate-preservation, longterm cycles, is clearly defined by fine aragonite minimum values in the deep periplatform sites, and by maximum fragmentation of pteropod tests in the shallow sites. Aragonite and planktonic 5 18 O records, usually in phase during the late Pleistocene, display, further back in time, discreet intervals where the two records do not match with one another. Major mismatches between both records occur synchronously in the Maldives and Bahamas periplatform sites and seem to correspond to extreme events of either carbonate-preservation or dissolution in the deep pelagic carbonate sites of the equatorial Pacific Ocean. Based on our findings, short-and long-term aragonite cycles can no longer be explained only by variations of aragonite input from the nearby shallow carbonate banks, in response to their alternate flooding and exposure through cyclic sea-level fluctuations. The aragonite long-term cycles in the periplatform environments are interpreted as carbonatepreservation cycles at intermediate-water depths. Their occurrence shows, therefore, that the carbonate chemistry of the entire water column has been influenced by long-term (0.5 m.y.) cyclic variations during the past 2.0 m.y. These major changes of the water-column carbonate chemistry are linked to the climate-induced carbon cycling among the different atmospheric, oceanic, and sedimentary carbon reservoirs.

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Marine carbonates

Cited by 44 publications

References 0 publications

The aftermath of the Carnian carbonate platform demise: a basinal perspective (Dolomites, Southern Alps)

The aftermath of the Carnian carbonate platform demise: a basinal perspective (Dolomites, Southern Alps)

ratios of modern marine calcite: Empirical indicators of ocean chemistry and precipitation rate

Pliocene-Pleistocene Aragonite Cyclic Variations in Holes 714A and 716B (the Maldives) Compared with Hole 633A (the Bahamas): Records of Climate-Induced CaCO3 Preservation at Intermediate Water Depths

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