Criteria for the retention of original seawater 87Sr86Sr in ancient shelf limestones

Denison, Rodger E.; Koepnick, Richard B.; Fletcher, Andrew; Howell, Michael L.; Callaway, W.S.

doi:10.1016/0009-2541(94)90110-4

Cited by 101 publications

(57 citation statements)

References 9 publications

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“…Denison et al, 1994;Baker et al, 1982;Veizer et al, 1983) and Precambrian Veizer, 1980, 1981;Veizer et al, 1983;Derry et al, 1989Derry et al, , 1992Asmerom et al, 1991;Kaufman et al, 1993 To further minimize contamination by foreign Sr associated with non-carbonate phases, processing of whole-rock samples ideally targets weak acid dissolution of less than 100% of the carbonate phase (Bailey et al, 2000). Accordingly, samples were leached using a volume of 1 N acetic acid sufficient to dissolve 90% of the total sample carbonate.…”

Section: Methodsmentioning

confidence: 99%

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

Miller

Alene

Sacchi

et al. 2003

Precambrian Research

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Juvenile continental crust of the Arabian-Nubian Shield (ANS) formed within a Neoproterozoic supercontinent cycle. Subsequent late Neoproterozoic deposition overlapped a series of dramatic climatic events that are unparalleled in subsequent Phanerozoic time, as proposed by the "Snowball Earth" hypothesis. In particular, extreme negative δ 13 C excursions coincident with glacial diamictite and cap carbonate sequences imply that profound carbon flux changes accompanied widespread glacial transitions (Snowball Events). Such a succession appears to be partially preserved in metasediments of the diamictite-bearing Tambien Group of northern Ethiopia (Negash syncline). Here, a pronounced negative carbon excursion from values of +7 to −2 per mil accompanies the transition to diamictite deposition. New zircon evaporation dates from granites intruding the base of the sequence but post-dating early deformation of the entire sequence suggest that the Tambien Group is older than 613 Ma, and therefore diamictite genesis is incompatible with younger Marinoan, Varanger, or "Ediacaran" glacial intervals. Syn-tectonic granites elsewhere within the region date between 750 and 800 Ma and provide an older age constraint for the Tambien Group. The limestone sequence underlying the diamictite has an average 87 Sr/ 86 Sr composition of 0.7066, which supports either a middle (ca. 750-740 Ma) or late (ca. 725-720 Ma) Sturtian age. Combined Sr and C isotopic compositions of the limestones and the upper age constraint from the granite ages provide a compelling argument that the Tambien Group sediments are ∼720-750 Ma or a little older and strongly support the prospect that the Negash diamictite is the product of Sturtian glaciation. If so, these are the first Sturtian Snowball Earth sequences identified in the ANS.

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Section: Methodsmentioning

confidence: 99%

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

Miller

Alene

Sacchi

et al. 2003

Precambrian Research

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“…Denison et al (1994a) measured isotope ratios of lime mudstones and wackestones from the USA whereas Martin & McDougall (1995) analysed conodonts from the USA and Pakistan. Denison et al (1994a, b) considered that as limemud-supported rocks excluded foreign pore fluids more effectively, they were more likely to retain the original seawater isotope composition. They adopted a rejection criterion of Sr/Mn>2 and Mn<300 ppm; however McArthur & Howarth (2004) used only some of the data from this suite of samples.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Lower Permian brachiopods from Oman: their potential as climatic proxies

Angiolini¹,

Darbyshire

Stephenson

et al. 2007

Earth and Environmental Science Transactions of the Royal Socie

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The Lower Permian of the Haushi basin, Interior Oman (Al Khlata Formation to Saiwan Formation/lower Gharif member) records climate change from glaciation, through marine sedimentation in the Haushi sea, to subtropical desert. To investigate the palaeoclimatic evolution of the Haushi Sea we used O, C, and Sr isotopes from 31 brachiopod shells of eight species collected bed by bed within the type-section of the Saiwan Formation. We assessed diagenesis by scanning electron microscopy of ultrastructure, cathodoluminescence, and geochemistry, and rejected fifteen shells not meeting specific preservation criteria. Spiriferids and spiriferinids show better preservation of the fibrous secondary layer than do orthotetids and productids and are therefore more suitable for isotopic analysis. 18 O of 3·7 to 3·1‰ from brachiopods at the base of the Saiwan Formation are probably related to glacial meltwater. Above this, an increase in 18 O may indicate ice accumulation elsewhere in Gondwana or more probably that the Haushi sea was an evaporating embayment of the Neotethys Ocean. 13 C varies little and is within the range of published data: its trend towards heavier values is consistent with increasing aridity and oligotrophy. Saiwan Sr isotope signatures are less radiogenic than those of the Sakmarian LOWESS seawater curve, which is based on extrapolation between few data points. In the scenario of evaporation in a restricted Haushi basin, the variation in Sr isotope composition may reflect a fluvial component.

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“…Once this is done, only samples identified as preserved may be used as proxy of original seawater chemistry (e.g., Brand and Veizer, 1980;Grossman, 1994;Brand, 2004). Some authors prefer to evaluate their complete sample collection as one using a fixed-chemistry approach of high Sr, low Mn and Fe contents (e.g., Joachimski et al, 2004), whereas others use Mn/Sr or some other ratios (e.g., Denison et al, 1994;Jacobsen and Kaufman, 1999), while others use similarities in isotopic trends after screening for anomalous elemental and isotopic…”

Section: Methodsmentioning

confidence: 99%

“…2). The northern Denison et al, 1994;Veizer et al, 1999). facies (Kane Springs Wash East, 543 ft thick [165.5 m]) contains more arenaceous sediments, but the carbonates are predominantly wacke-to packstones with a diverse fauna with many of the same taxa preserved in a similar manner as in the southern facies (Fig. 2).…”

Section: Paleoecologymentioning

confidence: 99%

Bathymetry and productivity of the southern Great Basin seaway, Nevada, USA: An evaluation of isotope and trace element chemistry in mid-Carboniferous and modern brachiopods

Brand

Webster

Azmy

et al. 2007

Palaeogeography, Palaeoclimatology, Palaeoecology

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The stable isotope and trace element chemistry of brachiopods from stratigraphically, paleontologically, and geochemically three coeval intervals about the mid-Carboniferous boundary in the Bird Spring Formation were evaluated for their potential of serving as proxies of bathymetry and productivity of the southern Great Basin seaway, an eastern arm of the Panthalassa Ocean. Oxygen isotopes delineate both spatial and temporal differences in values of brachiopods from the three coeval mid-Carboniferous sections. Based on pristine brachiopod δ 18 O values and supported by paleoecological information, water depth increased from Apex to Kane Springs Wash East to Arrow Canyon. In addition, there is also an increase in values from the latest Mississippian to the earliest Pennsylvanian suggesting a water temperature (cooling), a water depth (increase), and/or change in both of the habitat of the penecontemporaneous brachiopods.Analogous to values and trends observed in modern brachiopods, the Fe/Mn ratio of fossil counterparts may be a potential proxy of seawater productivity related to the micronutrient iron. Overall, the high ratios of Fe/Mn suggest highly productive waters for the southern Great Basin seaway, with somewhat reduced productivity during the earliest Pennsylvanian. In contrast, the carbon isotope values of the coeval material are relatively invariant with respect to productivity; trends similar to observations on modern carbonate allochems. Based on habitat and paleogeography, the Antler Orogenic Highlands west of the foreland basin are considered a potential source for the micronutrient iron enrichment of the carbonate platform shelf-edge environment. It is further postulated that upwelling currents, in part, which weakened from the latest Mississippian through to the earliest Pennsylvanian, may have transported the micronutrient iron onto the shelf/basin environments of the Bird Spring Formation of the southern Great Basin.

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Criteria for the retention of original seawater 87Sr86Sr in ancient shelf limestones

Cited by 101 publications

References 9 publications

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

Lower Permian brachiopods from Oman: their potential as climatic proxies

Bathymetry and productivity of the southern Great Basin seaway, Nevada, USA: An evaluation of isotope and trace element chemistry in mid-Carboniferous and modern brachiopods

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