Dolomitization of the late Cretaceous–Paleocene platform carbonates, Gölköy (Ordu), eastern Pontides, NE Turkey

Kırmacı, M. Ziya

doi:10.1016/j.sedgeo.2007.12.009

Cited by 31 publications

(16 citation statements)

References 51 publications

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“…3d), suggesting a change in the redox conditions and chemistry of the parent dolomitizing fluid during the course of crystallization (e.g. Rameil, 2008;Kırmacı, 2008). The same features have been also documented for the D2 phase of the Isthmus Bay section (Azmy et al, 2009;Conliffe et al, 2009), although the D2 crystals of the Isthmus Bay section were relatively smaller compared to those in the investigated core and do not exhibit sweeping extinction.…”

Section: Dolomite Petrography and Fluid Inclusionssupporting

confidence: 61%

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Dolomitization of the lower St. George Group on the Northern Peninsula in western Newfoundland: implications for lateral distribution of porosity

Azmy

Conliffe

2010

Bulletin of Canadian Petroleum Geology

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The Watts Bight Formation constitutes the lowermost part of the St. George Group in western Newfoundland. On the Northern Peninsula, it consists of Tremadocian (lower Ordovician) shallow marine platform carbonates (approximately 50 m thick). Dolomitization is extensive throughout the formation except for its topmost part. Petrographic examinations suggest that the succession was affected by at least three successive phases of dolomitization, which influenced secondary porosity. These phases have crystal-size ranges of approximately 4 to 50 µm (earliest sub-to euhedral dolomite D1), 50 to 200 µm (eu-to subhedral D2), and 300 µm to 3mm (anhedral saddle dolomite D3), respectively. They occur as replacement and/or pore-filling cements and exhibit dull (D1 and D3) to zoned (D2) luminescence under the cold cathodoluminoscope. The D2 phase is the dominant dolomite while the other two phases are rare.Microthermometric measurements of the primary two-phase fluid inclusions in D2 (homogenization temperatures up to 157 o C and salinity estimates up to 24.3 eq. wt% NaCl) suggest that it formed under relatively deep burial conditions. This is supported by the petrographic character (eu-to subhedral relatively big crystals) and geochemical composition (depleted δ 18 O mean value of -8.7±1.2‰ VPDB and low Sr contents of 68±30ppm) of the D2 phase. Thin-section examination suggests that porosity is dominantly intercrystalline and associated with the D2 phase. Visual estimates suggest that porosity varies from <1% in most of the formation to approximately 10% in two horizons, each approximately 2m thick, at approximately 10 m and 20 m from formation base. Correlations with the equivalent Watts Bight Formation section in the Isthmus Bay (300 km to South) reveal porous intervals at comparable stratigraphic levels. Also the geochemical results and microthermometric measurements suggest that D2 in the Northern Peninsula section was formed from hotter fluids under relatively more reducing conditions relative to their Isthmus Bay counterparts. The porous zones seem to be associated with fluctuations in sea-level marked by negative shifts in the δ 13 C profile. RÉSUMÉLa Formation de Watts Bight constitue l'unité la plus basse du Groupe de St.George dans l'ouest de Terre-Neuve. Dans la péninsule Great Northern, elle est composée de carbonates de plateaux marins (d'environ 50 m d'épaisseur) peu profonds du Trémadocien (Ordovicien inférieur). La dolomitisation est considérable dans toute la formation, à l'exception de sa partie la plus élevée. Les analyses pétrographiques donnent à penser qu'au moins trois épisodes de dolomitisation ont affecté la succession, ce qui a influencé la porosité secondaire. La taille des cristaux de ces épisodes de dolomitisation varie de 4 µm à 50 µm (dolomite D1 précoce de subautomorphe à automorphe), de 50 µm à 200 µm (D2 automorphe à subautomorphe) et de 300 µm à 3 mm (dolomite D3 en selle anédrique), respectivement. Ils se présentent sous forme de remplacement et/ou de cimentation d'espaces intergra...

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Section: Dolomite Petrography and Fluid Inclusionssupporting

confidence: 61%

“…The crystals vary in size between about 50 and 250 µm and exhibit cloudy cores with clear rims (e.g. Azmy et al, 2008Azmy et al, , 2009Kırmacı, 2008;Rameil, 2008;Conliffe et al, 2009) under plane polarized light ( Fig. 3b-d) and concentric zoned luminescence under CL (Fig.…”

Section: Figmentioning

confidence: 99%

Dolomitization of the lower St. George Group on the Northern Peninsula in western Newfoundland: implications for lateral distribution of porosity

Azmy

Conliffe

2010

Bulletin of Canadian Petroleum Geology

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“…The cloudy core with clear rims of D2 crystals indicate replacement of a precursor carbonate (cloudy core) and cementation (clear rim) whereas zoned CL images reflect chemical variations within the crystal (Warren, 2000). Undulose extinction in dolomites is caused by distorted crystal lattice that results from crystal growth at high temperatures (e.g., Warren, 2000;Rameil, 2008;Kırmacı, 2008). This is consistent with the mean Th (126.6 ± 12.8 o C, n ¼ 97) value of D2 and suggests crystallization at higher temperatures and deeper burial conditions relative to D1.…”

Section: Fluid-inclusion Gas Analysismentioning

confidence: 99%

Origin of Lower Ordovician dolomites in eastern Laurentia: Controls on porosity and implications from geochemistry

Azomani

Azmy

Blamey

et al. 2013

Marine and Petroleum Geology

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a b s t r a c tThe Catoche Formation of the St. George Group in eastern Laurentia (western Newfoundland) consists of early Ordovician (Arenigian) shallow marine platform carbonates (w160 m thick), which were extensively dolomitized during the course of their diagenetic history. The dolomites occur as both replacement and pore-filling cements and are a major control on porosity distribution in the formation. The origin and diagenetic history of the Catoche dolomites at Daniel's Harbour (western Newfoundland) were analysed in comparison to equivalent successions at Port au Choix (PaC) and Port au Port Peninsula (PaP) to assay the reservoir potential of these dolomites in eastern Laurentia. Petrographic examination identified at least three generations of dolomites in the Catoche Formation, which are: (1) an early replacement sub-to eu-hedral micritic dolomite (<4 mme30 mm, D1), (2) eu-to sub-hedral dolomite (70 mme1 mm) often with cloudy cores and clear rims (D2), and (3) subhedral to anhedral saddle dolomite cement (200 mme3 mm, D3). The micritic dolomite (D1) exhibits a dull cathodoluminescence (CL) under cathodoluminoscope, whereas dolomite D2 exhibits consistent concentric CL zonation. Some subhedral crystals of D3 appear zoned both in plane polarized light and cathodoluminoscope, otherwise D3 exhibits a dull CL. Stoichiometric dolomite occurs in all three generations with D2 as the dominant dolomite by abundance.The low strontium (47 ± 25 ppm) content coupled with depleted d 18 O value of dolomitizing fluids (-10 to -11.2& VSMOW) and near-micritic grain size, suggests an early precipitation of dolomite D1 at low temperatures of near-surface conditions from solutions likely formed by mixing of early Ordovician sea and meteoric waters. In contrast, microthermometric measurements of primary two-phase fluid inclusions in dolomite D2 (homogenization temperatures of 102e168 o C with a salinity range of 19.8e25 eq wt% NaCl) and dolomite D3 (homogenization temperatures of 158e190 o C with a salinity range of 20.2e22.2 eq wt% NaCl), suggest that both dolomite generations were generated in mid to deep burial settings from high salinity, low temperature (<200 o C) hydrothermal fluids likely under suboxic conditions. This is consistent with the low Sr concentrations for D2 (36.4 ± 8 ppm) and D3 (38.7 ± 9 ppm), d 18 O values of dolomitizing fluids for D2 (þ2.1 to þ8.1&, VSMOW) and D3 (þ6 to þ8.1& VSMOW), coupled with Fe contents of D2 (1684 ± 1096 ppm) and D3 (1783.7 ± 618 ppm) as well as the respective Mn (D2 ¼ 131.2 ± 50 and D3 ¼ 197.5 ± 55 ppm) concentrations.SREE and shale normalized (REESN) values of Catoche carbonates indicate enrichment in rare earth element (REE) composition of the earliest calcite (C1) relative to those of Arenig seawater, whereas the REESN profiles of the dolomite generations mimic that of calcite C1. The Ce (Ce/Ce*)SN and La (La/La* ¼ Pr/Pr*)SN anomalies of the Catoche dolomites are consistent with precipitation in equilibrium with source fluids in slightly oxic to suboxic conditions whereas Eu...

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“…This doiostone deposited in the initial phase of transgression (Wendte & Uyeno 2005), as shown by considerable depletion of S'^C signatures (Fig. 14), indicating precipitation in the conditions of mixing marine and meteoric waters (Immenhauser et al 2003;Kirmaci 2008;Kozlowski & Munnecke 2010). Type 1 dolomite was obviously formed in shallow-marine periphery of marine basins during early diagenesis.…”

Section: Discussionmentioning

confidence: 97%

Temporal evolution, petrography and composition of dolostones in the Upper Devonian Plavinas Regional Stage, southern Estonia and northern Latvia

Kleesment¹,

Urtson²,

Kiipli³

et al. 2013

Estonian J. Earth Sci.

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The Upper Devonian Plavinas Regional Stage in southern Estonia and northern Latvia is represented by dolostones containing interlayers of dolomitic marlstones and limestones. Petrographic, cathodoluminescence, electron microprobe and isotope techniques were used to investigate diagenetic evolution of dolostones. The rock succession has been affected by multiple diagenetic events. Based on petrographic and geochemical data, six dolomite textures were identified. The crystal size (5–1200 μm) and morphology of dolomites are variable. Commonly, dolomites are close to the stoichiometric composition, with low iron and manganese content. Their stable isotope composition (δ13C, δ18O) differs greatly from that of dolomite precipitated from Frasnian seawater. Dolomitization is more pronounced in the lower part of the studied sequence, in the Snetnaya Gora Formation and Lower Pskov unit where carbonates are completely dolomitized, whereas upwards in the section the dolomite content decreases. Voids and pores of the Lower Pskov unit are mainly open, but partly or completely occluded in the Upper Pskov unit. Void-filling dolomite has slightly and void-filling calcite notably depleted stable isotope signatures. Major dedolomitization and calcite-filling processes took place during the final uplift and emergence of the northern part of the Baltic basin, connected with the migration of karst-related meteoric waters into previously dolomitized horizons within carbonate rocks

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Dolomitization of the late Cretaceous–Paleocene platform carbonates, Gölköy (Ordu), eastern Pontides, NE Turkey

Cited by 31 publications

References 51 publications

Dolomitization of the lower St. George Group on the Northern Peninsula in western Newfoundland: implications for lateral distribution of porosity

Dolomitization of the lower St. George Group on the Northern Peninsula in western Newfoundland: implications for lateral distribution of porosity

Origin of Lower Ordovician dolomites in eastern Laurentia: Controls on porosity and implications from geochemistry

Temporal evolution, petrography and composition of dolostones in the Upper Devonian Plavinas Regional Stage, southern Estonia and northern Latvia

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