Ancient subaerial exposure and freshwater leaching in sandstones

Emery, D.; Myers, Keith; Young, Reginald H.F.

doi:10.1130/0091-7613(1990)018<1178:aseafl>2.3.co;2

Cited by 71 publications

(44 citation statements)

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“…Petro graphic evidences suggest an origin for young kaolinite associated with telodiagenesis by the infl ux of meteoric waters during uplift (i.e. Emery et aL 1990;Ketzer et aL 2003;Worden and Morad 2003). At this stage of kaol inite generation, replacements of micas (already de fonned by mechanical compaction), occurred.…”

Section: T-ii T-i T-i T-ii T-i T-ii T-i T-i T-ii T-ii T-ii T-ii T-ii mentioning

confidence: 99%

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain

Ochoa

Arribas

2005

Int J Earth Sci (Geol Rundsch)

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Buntsandstein deposits generated in a slowly subsiding basin on the western margin of the Iberian Chain are represented by a stratigraphic succession of fluvial deposits less than 100 m thick (conglomerates, sandstones, and shales). Diagenetic processes in sand stones can be grouped as eodiagenetic, mesodiagenetic, and telodiagenetic. Eodiagenesis can be associated with Muschelkalk, Keuper, and probably early Juras sic times. Mesodiagenesis is probably related to Jurassic times. Diagenetic chemical reactions suggest a maximum burial less than 1.5 km and low tempera tures « 120°C). Patterns of porosity reduction by compaction and cementation suggest four diagenetic stages: (1) Loss of primary porosity by early mechanical compaction; (2) early cementation (K feldspar and dolomite); (3) dissolution of cements; and (4) framework collapse by re-compaction. These stages are manifested by the presence of two types of sand stone. Type I sandstones present high intergranular volume (mean, 30%). Type II sandstones are charac terized by high compactional porosity loss and exhibit low values of intergranular volume (mean, 16.9%). Type 11 sandstones are associated with the dissolution of cement and later re-compaction of type I sand stones. An intermediate telodiagenetic phase is de duced and related to the sharp unconformity between Lower Cretaceous sediments and the underlying sedi ments. This suggests that a mechanically unstable framework collapsed during the Cretaceous, generating type II sandstones. The analyzed diagenetic paths have a wide applicability on similar marginal areas of rift basins.

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Section: T-ii T-i T-i T-ii T-i T-ii T-i T-i T-ii T-ii T-ii T-ii T-ii mentioning

confidence: 99%

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain

Ochoa

Arribas

2005

Int J Earth Sci (Geol Rundsch)

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“…The general Copyright 9 1993, The Clay Minerals Society diagenetic sequence and pore fluid hydrologic regime have been discussed by Macaulay et al (1992a) and the carbonates treated in detail by Macaulay et al (1993). Of particular relevance to the present paper are the illitic clay study by McHardy et al (1982), and the discussion by Emery et al (1990a)--following De'Ath and Schuyleman (1981)--of potassium feldspar dissolution and kaolinite precipitation. Relationships between variations in kaolinite morphology and stable isotopic ratios (5180, ~D) are presented in Macaulay et al (1992b).…”

Section: Introduction and Geological Settingmentioning

confidence: 99%

“…The oil source rocks for the reservoir are the organic-rich Kimmeridge Clay Formation mudstones. During the early Cretaceous, there was tectonic uplift, tilting, and resultant erosion of the crest of the Magnus structure, with meteoric water penetrating the sandstones (De'Ath and Schuyleman, 1981;Emery et aL, 1990a;Macaulay et aL, 1992a). Subsequently, a seal was formed by a one kilometer or so thickness of Upper Cretaceous muds and marls.…”

Section: Introduction and Geological Settingmentioning

confidence: 99%

Implications of Linearly Correlated Oxygen and Hydrogen Isotopic Compositions for Kaolinite and Illite in the Magnus Sandstone, North Sea

Fallick

Macaulay

Haszeldine

1993

Clays and clay miner.

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Abstraet--Authigenic kaolinite and illite are important diagenetic minerals in the Magnus Sandstone, a giant oil reservoir in the northern North Sea. These clay minerals, separated from three wells, show considerable ranges in their oxygen isotopic composition (618OsMow = + 9 to + l 6%o) and hydrogen isotopic composition (fiDsMow = --55 to --105%). The variations in 618 O and 6D are positively linearly correlated with a high degree of statistical significance for both kaolinite and illite:Kaolinite: n = 12; 6D = 6.1 ~180 -169; r = 0.66(>95%) Illite: n = 11; riD = 5.96~80 -159; r = 0.78(>99%).Formation of the clays in a pore fluid of uniform isotopic composition over a range of temperatures appears unlikely. It is suggested that the observed relationships between clay mineral 6~sO and 6D are perhaps best explained by a model of precipitation at more or less constant temperature from pore fluids which varied isotopicaUy across the oilfield. The isotopic composition of the formation waters would then lie along the line: fiDw = 6.2 b'8Ow -50. This is most plausibly interpreted as a mixing line with suggested minimal endmembers at (btsO, ~D) values of (+4, -24) and (-4, -76). The first of these represents reasonable isotopic values for Magnus Sandstone formation waters. Although fi~80 of the second is compatible with an evolved Cretaceous meteoric water, its 6D value is difficult to understand in the context of the model.

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“…Position of the sequence boundary at the studied section Feldspar leaching and the associated production of abundant kaolinite can be used to infer the past interaction of meteoric water with sandstone and, more generally, that kaolinite is indicative of unconformities (Tardy, 1971;Emery et al, 1990). In this context, the relative abundance of authigenic kaolinite/dickite may be used as an indicator of an unconformity.…”

Section: Discussionmentioning

confidence: 99%

“…The influx of meteoric acidic water into the sandstones below the sequence boundary may result in an increase in intergranular porosity and permeability of the sandstones by the dissolution of feldspar; at the same time, this process may also result in the formation of authigenic minerals such as kaolinite and silica cement (BjØrlykke, 1984;Emery et al, 1990). The development of authigenic pore-filling kaolinite modifies the amounts of available porosity and permeability.…”

Section: Evolution Of Reservoir Quality In the Sandstonesmentioning

confidence: 99%

Predictive diagenetic clay-mineral distribution in siliciclastic rocks as a tool for identifying sequence boundaries in non-marine successions: the Coalspur Formation, west-central Alberta

Khidir¹,

Catuneanu²

2009

Geologos

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The study of upper Cretaceous -lower Tertiary fluvial deposits of the Coalspur Formation in the Foothills region of west-central Alberta reveals that the distribution of early authigenic kaolinite has a well-defined relation to the sequence stratigraphic framework. In this context, it has been observed that the kaolin mineral content increases in sandstones lying below subaerial unconformities, which mark the most significant stratigraphic hiatuses and hence the sequence boundaries in fully fluvial successions. The increased abundance of authigenic kaolinite immediately below sequence boundaries may have been caused by the infiltration of meteoric water during times of subaerial erosion, resulting in the dissolution of unstable minerals (e.g., micas and feldspar) and the formation of kaolinite and secondary porosity. It is therefore suggested that the change in clay mineral assemblages in the stratigraphic section depends in part on the position of the analyzed sandstone samples relative to the sequence boundaries. In a larger context, the method of using authigenic clays to delineate depositional sequences in non-marine successions needs to be evaluated on a caseby-case basis, as the diagnostic early diagenetic minerals underlying the sequence boundary may change as a function of palaeoclimate and also as a function of late diagenetic processes.

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Ancient subaerial exposure and freshwater leaching in sandstones

Cited by 71 publications

References 0 publications

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain

Diagenetic paths in the margin of a Triassic Basin: NW zone of the Iberian Chain, Spain

Implications of Linearly Correlated Oxygen and Hydrogen Isotopic Compositions for Kaolinite and Illite in the Magnus Sandstone, North Sea

Predictive diagenetic clay-mineral distribution in siliciclastic rocks as a tool for identifying sequence boundaries in non-marine successions: the Coalspur Formation, west-central Alberta

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