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| Titel |
Petrographic and geochemical characteristics of dolomitization in the Late Jurassic-Early Cretaceous platform carbonates, Başoba Yayla (Eastern Pontides, NE Turkey) |
| VerfasserIn |
Merve Yıldız, M. Ziya Kırmacı, Raif Kandemir, Tuğba Eroğlu |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101442
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| Publikation (Nr.) |
 EGU/EGU2015-1478.pdf |
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| Zusammenfassung |
| The Late Jurassic-Early Cretaceous Berdiga Formation with a wide distribution in E-W
direction in the eastern Pontides (NE Turkey) is composed of platform carbonates. The
formation with distinct lithofacies properties in both lateral and vertical directions was
deposited on carbonate shelf changing from supratidal to platform margin reef and was buried
until the end of Late Cretaceous. One of the typical exposures of formation is found around
the Başoba Yayla area (Trabzon, NE Turkey) in northern zone of the eastern Pontides where
the formation has a limited distribution. In this area, platform carbonates are 250 m in
thickness and from bottom to top composed of dolomite, grainstone-packstone and
skeleton wackestone. The 120-m thickened dolomite facies which comprises the
lower part of formation contains four dolomite phases as replacement (Rd) and
cement (Cd) types. Replacement dolomites (Rd) that are cut by low-amplitude
stylolites are developed as 1) thin crystalline planar-s dolomite (Rd1), 2) thin-medium
crystalline, texture-protective planar-s dolomite (Rd2) dolomite and 3) medium-coarse
crystalline planar-s dolomite (Rd3). Coarse-very coarse crystalline dolomite cement
(Cd) filling dissolution spaces and fractures in Rd1 dolomites are cogenetic with
low-amplitude stylolites. Replacement dolomites are Ca-rich and non-stoichiometric
(Ca56-60Mg40-44) and geochemically have two-population distribution and uniform dull
red/non-luminescence appearance. The δ18O compositions of replacement dolomites are
from -15.3 to -4.2 oVPDB, δ13C values are 1.5–3.7 oVPDB and 87Sr/86Sr ratios are
0.70675 to 0.70731. Sr, Na, Mn and Fe contents of these dolomites are 74–163 ppm,
bdl–200 ppm, 94–553 ppm and 1400–3800 ppm, respectively. Petrographic and
geochemical date yield that replacement dolomites (Rd) are formed before the chemical
compression at shallow-moderate burial depths from Jurassic-Early Cretaceous seawater
and/or seawater partly modified by rock-water interaction and recrystallized by
hydrothermal waters of marine origin at enhanced temperatures and progressing
burial depths. Like replacement dolomites, dolomite cement (Cd) are Ca-rich and
non-stoichiometric (Ca58-60Mg40-42) and are represented by Sr (106-201), Na ( |
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