Ordovician meteoric carbon and oxygen isotopic values: implications for the latitudinal variations of ancient stable isotopic values

Tobin, Kenneth J.; Steinhauff, D. Mark; Walker, Kenneth R.

doi:10.1016/s0031-0182(98)00221-1

Cited by 13 publications

(12 citation statements)

References 26 publications

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“…Specific patterns in carbon and oxygen isotope data (Allan & Matthews, 1982; Joachimski, 1994; Wagner et al. , 1995; Tobin et al. , 1999; Immenhauser et al.…”

Section: Characteristics Of the Top Shu’aiba Discontinuity Surface Inmentioning

confidence: 99%

“…Whereas much of this pore space is probably late in origin, pores infilled by meteoric cements are considered to be: (i) Aptian in age; and (ii) related to a phase of Aptian subaerial exposure. Specific patterns in carbon and oxygen isotope data (Allan & Matthews, 1982;Joachimski, 1994;Wagner et al, 1995;Tobin et al, 1999;Immenhauser et al, 2008), as well as in trace element abundances (Wagner et al, 1995;Immenhauser et al, 2000b), are considered to be indicative of subaerial exposure of former carbonate sea floors. The depletion in 13 C beneath a discontinuity surface commonly results from emergence, carbonate dissolution and re-precipitation of meteoric cements that comprise isotopically light soil CO 2 .…”

Section: Features Related To a Subaerial Exposure Stagementioning

confidence: 99%

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Surfaces with a long history: the Aptian top Shu’aiba Formation unconformity, Sultanate of Oman

et al. 2011

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Discontinuity surfaces in shallow‐marine carbonate successions may represent significant time gaps in the geological record of ancient epeiric‐neritic seas. Understanding the hidden geological information contained in major discontinuities is thus of key significance in palaeo‐environmental analysis, sequence stratigraphy, reconstructions of sea‐level change and basin evolution. In the present paper, the Aptian top Lower Shu’aiba Formation discontinuity in the Sultanate of Oman is taken as a prominent example of a regionally extensive (>100 000 km2) surface with a long (up to 10 Myr) and complex geological history. The top Shu’aiba discontinuity formed on the topographically elevated domain of the Oman platform and represents in essence the Late Aptian time interval. Coeval carbonates in the intrashelf Bab Basin and oceanic rim indicate forced regression and sequence‐wise, gradual down‐stepping. Available regional, sedimentological, sequence‐stratigraphic, petrographic, palaeontological and geochemical evidence from outcrops and cored wells in Oman is summarized, in part complemented by new data, and reviewed in a process‐oriented context. In the field, the discontinuity is expressed as a low relief, stained surface with evidence for a marine hardground stage being dominant. Indistinct features that indicate a transient meteoric precursor stage (isotope shifts, meteoric cements, circumgranular cracks, etc.) are present but their interpretation requires careful and detailed work. This feature is remarkable, as a series of relative sea‐level falls with amplitudes of up to several tens of metres from the Early to Late Aptian boundary to the end of the Aptian are reported from the Middle East and elsewhere. Despite the palaeogeographic position of the study area in the tropical climate zone, evidence of deep‐cutting karst features, characteristic for many long‐term exposure surfaces worldwide is scarce. Acknowledging the fact that the modern world offers no genuine analogues for the Lower Aptian carbonate system in Oman, morphological similarities between actualistic, wave‐eroded coastal terraces and the top Shu’aiba discontinuity are discussed critically. This discussion may imply that, during an exposure time of several million years, the top Shu’aiba discontinuity experienced repeated stages of shallow flooding and emergence, with each transgression removing portions of the underlying rock record. The data shown here exemplify the complexity of hiatal surfaces in epeiric‐neritic carbonates and may serve as a case example for other major discontinuities.

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“…Specific patterns in carbon and oxygen isotope data (Allan & Matthews, 1982; Joachimski, 1994; Wagner et al. , 1995; Tobin et al. , 1999; Immenhauser et al.…”

Section: Characteristics Of the Top Shu’aiba Discontinuity Surface Inmentioning

confidence: 99%

Section: Features Related To a Subaerial Exposure Stagementioning

confidence: 99%

Surfaces with a long history: the Aptian top Shu’aiba Formation unconformity, Sultanate of Oman

et al. 2011

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“…Depending on substrates, this calcite precipitated in two distinctive but contemporaneous forms: (1) syntaxial cements on echinoderm debris, and (2) thin isopachous cements (smaller than 30 mm) formed by small crystals scattered on the surface of the grains. This cement now consists of non-ferroan low magnesian calcite (LMC) which exhibits a mottled luminescence typical of replacement of high magnesian calcite (HMC) by LMC (Grover and Read, 1983;Braithwaite and Heath, 1992;Tobin et al, 1999).…”

Section: Diagenetic Stratigraphymentioning

confidence: 99%

Burial dissolution of micrite in Middle East carbonate reservoirs (Jurassic–Cretaceous): keys for recognition and timing

Lambert

Durlet

Loreau

et al. 2006

Marine and Petroleum Geology

168

114

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“…These d 18 Ov-SMOW values differ from the d 18 O composition of contemporary CambrianeOrdovician seawater (À5 to À7&; cf. Veizer et al, 1997) and meteoric water, which was slightly lighter than seawater (between À8 and À9&; Tobin et al, 1999). This indicates that the carbonate cement did not precipitate from eogenetic depositional waters (CambrianeOrdovician seawater and meteoric water), or from mesogenetic evolved CambrianeOrdovician formation water.…”

Section: Mesogenetic and Telogenetic Alterationsmentioning

confidence: 93%

Linking diagenesis to sequence stratigraphy in fluvial and shallow marine sandstones: Evidence from the Cambrian–Ordovician lower sandstone unit in southwestern Sinai, Egypt

Kordi

Turner

Salem

2011

Marine and Petroleum Geology

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Ordovician meteoric carbon and oxygen isotopic values: implications for the latitudinal variations of ancient stable isotopic values

Cited by 13 publications

References 26 publications

Surfaces with a long history: the Aptian top Shu’aiba Formation unconformity, Sultanate of Oman

Surfaces with a long history: the Aptian top Shu’aiba Formation unconformity, Sultanate of Oman

Burial dissolution of micrite in Middle East carbonate reservoirs (Jurassic–Cretaceous): keys for recognition and timing

Linking diagenesis to sequence stratigraphy in fluvial and shallow marine sandstones: Evidence from the Cambrian–Ordovician lower sandstone unit in southwestern Sinai, Egypt

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