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首页> 外文期刊>Facies >The mid-Cretaceous Debarsu Formation (Upper Albian-Middle Turonian) of Central Iran: depositional environment, palaeogeography, and sequence stratigraphic significance
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The mid-Cretaceous Debarsu Formation (Upper Albian-Middle Turonian) of Central Iran: depositional environment, palaeogeography, and sequence stratigraphic significance

机译:伊朗中部中间白垩纪的黛尔斯组(上部奥尔代尼亚 - 中间涡轮):沉积环境,古地理和序列地层意义

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The Upper Albian-Turonian Debarsu Formation in its type area around Haftoman, south of Khur (Central Iran) has been investigated using an integrated approach of high-resolution logging, bio- and sequence stratigraphic dating, and facies analysis based on field observations and detailed microfacies studies. The up to 500-m-thick Debarsu Formation consists of stacked, several 10- to similar to 100-m-thick, essentially asymmetric shallowing-upward cycles from grey offshore marl via skeletal and intraclastic limestone with large-scale clinoformed foresets to thick-bedded bioclastic, locally rudist-bearing shallow-marine topset strata capped by palaeokarst surfaces. The diverse (micro)facies inventory (29 facies types) is dominated by skeletal carbonates (bioclastic pack-, grain-, float- and rudstone) that reflect deposition on a carbonate ramp with a lagoonal shoreline that was attached to an elevated area in the west and southwest. The outer ramp facies association of the Debarsu ramp contains predominantly microbioclastic marl with open-marine microfossils (planktic foraminifera) and fine-grained bioturbated packstone. The transition into the mid-ramp facies association, dominated by bioclastic pack- and grainstone (foreset strata), is commonly gradational. The inner-ramp facies association is very diverse, mainly consisting of high-energy (well-washed and cross-bedded) grainstone as well as back-ramp or inter-shoal bioclastic float- and rudist bafflestone. The Debarsu Formation occurs in an area of more than 2500 km(2) to the west, southwest, and south of Khur but had its depocenter with maximum thicknesses and thick offshore marl intervals in the type area. The large-scale shallowing-upward cycles correspond to third-order depositional sequences. The chronostratigraphic positions of the sequence-bounding unconformities in the Upper Albian to Lower Cenomanian match equivalent surfaces known from other Cretaceous basins on different tectonic plates. However, a large-s
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