The Jurassic Lower Carbonate Group in the Aïn Ouarka area of Western Saharan Atlas, Algeria, is represented by six formations, from base to top: Hettangian Chemarikh Dolostone, Early Sinemurian–Pliensbachian Aïn Ouarka Limestone, Toarcian Aïn Rhezala Limestone, Aalenian–Late Bajocian Raknet El Kahla Limestone Breccia, Late Bajocian Theniet El Klakh, and Late Bajocian–Bathonian Tifkirt Limestone formations. From the microfacies analysis, six microfacies types (MF1–MF6) have been recognized and grouped into three associations developed during a transgressive–regressive cycle: (a) inner ramp facies association; (b) middle ramp facies association; and (c) outer ramp facies association. The mineralogical analysis of the carbonate rocks reveals that they contain mostly low-Mg calcite associated with ankerite, pyrite, and other detrital minerals such as quartz, chlorite, illite, feldspar (albite), and a few clay minerals. These minerals could be related to the deep fluid and hydrocarbon circulations during deposition. The isotopic data display a variation of δ¹³C isotopic values between −5.14‰ and +2.21‰ (VPDB) and between −8.12‰ and −4.95‰ for δ¹⁸O values (VPDB). The set of δ¹³C values is similar to the signature of marine dissolved inorganic carbon. First of all, the positive values of δ¹³C show that the origin of carbon is not from the organic-rich zone (microbial zone), but probably derived from pore-water and/or biogenic carbonate precursors. On the other hand, the negative values of δ¹³C indicate that the carbon may result from organic sources linked to the sulphate reduction bacteria activity, or by a heightened volcanic and/or hydrothermal activities releasing light carbon (¹²C). The negative δ¹⁸O values are not consistent with marine water ambient temperature, but with a possible influence of diagenesis or increasing of temperature by hydrothermal water. This hydrothermal activity is controlled by synsedimentary faults during the Early Jurassic and related to a late pulse of the Central Atlantic Magmatic Province (CAMP) volcanism and by regional volcanism during the Middle Jurassic (Bajocian–Bathonian).

中文翻译：

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西撒哈拉阿特拉斯（阿尔及利亚艾因瓦尔卡地区）下-中侏罗统碳酸盐岩的微相和稳定同位素特征

阿尔及利亚西撒哈拉阿特拉斯阿因瓦尔卡地区侏罗纪下碳酸盐岩群由六个地层代表，从底部到顶部：赫唐阶 Chemarikh Dolostone、早辛尼穆阶-普连斯巴阶 Aïn Ouarka 石灰岩、Toarcian Aïn Rhezala 石灰岩、Aalenian-Late El Kahla 石灰岩角砾岩、晚 Bajocian Theniet El Klakh 和晚 Bajocian-Bathonian Tifkirt 石灰岩地层。从微相分析中，已识别出六种微相类型（MF1-MF6），并将其分为三个在海进-回归循环中形成的关联：(a) 内斜坡相关联；(b) 中斜坡相协会；(c) 外斜坡相组合。碳酸盐岩的矿物学分析表明，它们主要含有低镁方解石，伴生铁橄榄石、黄铁矿、和其他碎屑矿物，如石英、绿泥石、伊利石、长石（钠长石）和一些粘土矿物。这些矿物可能与沉积过程中的深层流体和碳氢化合物循环有关。同位素数据显示了δ ¹³ C 同位素值介于− 5.14‰ 和 +2.21‰ (VPDB) 之间，δ ¹⁸ O 值介于− 8.12‰ 和− 4.95‰之间(VPDB)。一组δ ¹³ C 值类似于海洋溶解无机碳的特征。首先，δ ¹³ C的正值表明碳的来源不是来自富含有机物的区域（微生物区），而可能来自孔隙水和/或生物碳酸盐前体。另一方面，δ ¹³的负值C 表明碳可能来自与硫酸盐还原细菌活动相关的有机源，或由释放轻碳 ( ¹² C) 的火山和/或热液活动加剧所致。负的δ ¹⁸ O 值与海水环境温度不一致，但可能受成岩作用或热液温度升高的影响。这种热液活动受早侏罗世的同沉积断层控制，与中大西洋岩浆区 (CAMP) 火山活动的晚期脉冲和中侏罗世（巴约阶-巴松阶）的区域火山活动有关。