Carbonate Platform-Margin Architecture and Its Influence On

Marine and Petroleum Geology 68 (2015) 291e306

Contents lists available at ScienceDirect

Marine and Petroleum Geology

journal homepage: www.elsevier.com/locate/marpetgeo

Research paper Carbonate platform-margin architecture and its inﬂuence on Cambrian-Ordovician reef-shoal development, Tarim Basin, NW China

* Zhiqian Gao , Tailiang Fan

Key Laboratory for Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, Ministry of Education of China, China University of Geosciences, Beijing 100083, China article info abstract

Article history: Six types of carbonate platform marginal slope have been identiﬁed in the Cambrian-Ordovician of Received 10 February 2015 Tarim Basin. These include a progradational carbonate ramp platform, a progradational carbonate Received in revised form rimmed platform, an aggradational rimmed carbonate platform, a retrogradational rimmed carbonate 9 June 2015 platform, an aggradational margin on an isolated carbonate platform and a retrogradational margin on Accepted 26 August 2015 a submerged carbonate platform. Various platform margin architectures and reef-shoal characteristics Available online 28 August 2015 occur in different areas of the Tarim basin. A progradational carbonate ramp platform margin began in the Early Cambrian in the Tarim basin. A progradational rimmed platform margin developed in the Keywords: Carbonate platform Middle Cambrian time in the northern Tarim basin, whereas contemporaneously a progradational ramp Cambrian-Ordovician platform margin developed in the southwestern and central Tarim basin. A retrogradational rimmed Tarim basin carbonate platform developed in the northern Tarim basin, whereas an aggradational rimmed car- Platform architecture bonate platform occupied the central Tarim basin in the Early Ordovician time. An aggradational Platform evolution margin on an isolated platform and a retrogradational margin on a submerged platform developed mainly during the Late Ordovician in the central Tarim basin. Platform margin-slopes migrated continually throughout the Cambro-Ordovician. The broad platform area (western Tarim Platform) that occupied most of the northwestern and central Tarim Basin in the Early Cambrian time was split by an east-west oriented shelf seaway that began to develop along the eastern and western margins of the platform in the Early Ordovician time and completely transected the platform by Late Ordovician time. The resultant central Tarim Basin platform area was much reduced, elongate east-west around the Central Tarim paleo-uplift, and terminated eastward towards region of the Late Ordovician basinal deposition across the eastern Tarim Basin. Affected by platform margin structure, Climate and paleo- depth, algal reefs and shoals developed mainly in the Cambrian, and intraclastic shoals developed mainly in the Early Ordovician, followed by reef-building of framestone or bafﬂestone in the Late Ordovician. © 2015 Elsevier Ltd. All rights reserved.

1. Introduction control the overall geometry and internal stratal anatomy of carbonate platform margins is of paramount importance for sequence Carbonate platform margins are sensitive to changes in sea level, stratigraphy, seismic interpretation, hydrocarbon exploration, and climate, productivity, tectonic activity and sediment input (Scott, reservoir characterization (Schlager and Camber, 1986; Eberli and 1993; Pomar et al., 2005; Heldt et al., 2010; Phelps et al., 2014). Ginsburg, 1989; Kenter, 1990; Schlager et al., 1994; Kenter et al., The successions deposited on platform margins are particularly 2005; Santantonio et al., 2013). Oil and gas field controlled by interesting because they record the changes of carbonate platforms reef-shoal reservoirs in platform margin is an important compo- and their relation to adjacent basins (Graziano, 2000; Castro et al., nent of carbonate oil and gas fields. As of 2012, 99 of the 179 giant 2008; Santantonio et al., 2013). Understanding the processes that carbonate oil and gas fields globally are oil and gas fields controlled by reef-shoal reservoirs (Halbouty, 2003; Jiang et al., 2008; Gu et al., 2012). Carbonate successions account for only about 20% of the global sedimentary strata, but oil and gas resources in carbonate * Corresponding author. strata are about 52% of the world's total reserves (Fan et al., 2007; E-mail address: [email protected] (Z. Gao). http://dx.doi.org/10.1016/j.marpetgeo.2015.08.033 0264-8172/© 2015 Elsevier Ltd. All rights reserved. 292 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306

Jiang et al., 2008). within Series 2 and Series 3, and the Late Cambrian strata are The study area, Tarim Basin, is located in the southern part of the Furongian. The Ordovician is divided into 3 Series (Early, Middle Xinjiang Uygur Autonomous Region in northwestern China and and Late Ordovician) and 5 Formations (Penglaiba, Yingshan, between the Tianshan and Kunlun Mountains, and occupies an area Yijianfang, Lianglitage and Sangtamu Formation) (Fig. 1c; Zhao of some 56 Â 104 km2 (Fig. 1a and b). It is the largest petroliferous et al., 1997; Wang, 1999). superposed basin in China, characterized by a long history of The platform margin slope is important because the source of deposition, a thick stratigraphic succession, a complex tectonic sediment for lime-mud mounds and bank-reef reservoir facies are history and abundant hydrocarbon resources (Fig. 1c; Gao et al., developed there and its development is controlled by the platform 2006a, b; Fan et al., 2007; Gao and Fan, 2014a). Carbonate succes- type. Research on the carbonate platforms in Tarim Basin have been sions are common globally in the Cambrian and Ordovician and are focused on platform types (Gao et al., 2006b; Gu et al., 2009; Yu and typically very thick in the Tarim Basin. Total areas of about Jin, 2011; Gao et al., 2012), sedimentary environment (Feng et al., 300 Â 104 km2 of carbonate rocks occur in China, of which 2006, 2007; Hu et al., 2009; Kong and Cheng, 2010; Jiao et al., 56 Â 104 km2 occupy the lower Paleozoic of the Tarim Basin in NW 2011), sequence stratigraphy (Zhang and Liu, 1995; Fan, 1998; Pan China. The lower Paleozoic carbonate strata of Tarim Basin are rich et al., 2011) and reef-shoal distribution (Gao et al., 2005; Wang in oil and gas resources. Until 2015, the Tahe oil-ﬁeld with et al., 2007; Yang et al., 2011; Han et al., 2011) of separate parts of 12.96 Â 108 tonnes reserves and the Central Tarim oil-ﬁeld with the Cambro-Ordovician in separate parts of the Tarim Basin. 2.7 Â 108 tonnes reserves were discovered in Cambrian-Ordovician Affected by regional dynamics, paleo-depth, relative sea level carbonate formations, and new exploration breakground had been change and carbonate sedimentation rate, the geometry, lateral made in carbonate formations in Shunnan area of the Tarim basin extent and disposition of platform margin slope strata lithofacies (Kang, 1985; Zhang et al., 2007; Jin et al., 2009; Sun, 2011; Yang may vary throughout the Cambrian and Ordovician of the Tarim et al., 2011; Gao and Fan, 2014a, b; Zheng et al., 2015). The Basin (Henry and George, 1977; Pigram et al., 1989; Gao et al., Cambrian and Ordovician are the main carbonate successions in the 2006a). The changes and migrations of platform margins Tarim Basin. The Cambrian is divided into 3 Series (Early, Middle controlled the distribution of facies and determined the develop- and Late Cambrian) and 6 Formations (Yuertusi, Xiaoerbulake, ment of source rocks, reservoirs, and regional cap rocks (Gao et al., Wusonggeer, Shayilike, Awatage and Qiulitage Formation) (Fig. 1c; 2006b, 2011, 2012). Former research on carbonate platforms in Zhao et al., 1997; Wang, 1999). The Early Cambrian strata corre- Tarim Basin is absent of depiction of margin architectures and spond to Terreneuvian in West literature, the Middle Cambrian falls platform type evolution.

Fig. 1. Location map of the Tarim Basin in China. These uplifts, slopes and depressions in Fig. 1B, such as Northern Tarim Uplift, Aman Slope, and Manjiaer Depression, are tectonic 0 2 1 0 8 units of the Tarim Basin. In Figs. 1C, T9 is base of Cambrian, T8 is base of Middle Cambrian, T8 is base of Late Cambrian, T8 is base of Ordovician, T7 is base of Early Ordovician Yingshan 4 2 0 Formation, T7 is base of Late Ordovician, T7 is base of Late Ordovician Lianglitage Formation, T7 is top of Ordovician. Three red lines, such as Line 1, Line 2 and Line 3, are seismic lines that are used to interpret platform architectures in different areas of the Tarim Basin. (For interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.) Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 293

Our study is based on a grid of 2D seismic profiles, two 3D 3. Data presentation and interpretation seismic surveys and re-interpreted 120 wells, and has the following aims: to analyze changes of platform-margin types and margin 3.1. Seismic data architectures in different areas, to clarify sedimentation variations across the platforms, to establish an evolutionary model for plat- 3.1.1. Line 1 in Northern Tarim area form types, and to outline the distribution of the reef-shoals along Line 1 (seismic profile AKKL08-NWW-2) in the Northern platform-margins. Tarim area (Figs. 1 and 2), extends southeast from Tabei Uplift to the Manjiaer Depression (Fig. 1, Gao and Fan, 2014a). The burial depth of the entire Cambrian to Lower Ordovician succession 2. Methods and database increases abruptly southeast at about shot-point 106,300 from a mean two-way travel time of about 4.25 s to about 5.25 s The database used for this study consists of wells, outcrops and (Figs. 3 and 4). There were eight progradational reflection se- fl seismic re ection data and includes (Fig. 2): quences in the Cambrian (two in the Upper Cambrian, four in the MiddleCambrianandtwointheLowerCambrian)(Figs. 3 and 4). fi 1) A sparse grid of 2D regional seismic pro les which are 21 green Every progradational sequence tract reflection contact with a seismic lines (Fig. 2) (CNPC China database). hummocky reflection sequence. The four progradational depo- fi 2) 2D commercial seismic pro les which are 512 black and sitional sequences of the Middle Cambrian become slightly more red seismic lines (Fig. 2), mainly concentrated in the Central aggradational than the underlying two progradational deposi- Tarim, Northern Tarim and Bachu areas (Sinopec China tional sequences in the Lower Cambrian. Each of these represents database). a complete transgressive-regressive depositional sequence. Un- 3) 3D seismic surveys acquired over the Central Tarim area within like the Cambrian, there are five retrogradational reflection the Sinopec permit (Fig. 2) (Sinopec China database). sequences in the Lower Ordovician (one in the Lower Ordovician 4) Logs for 120 wells (Fig. 2), corresponding to 425 m of stratig- Penglaiba Formation and four in the Lower Ordovician Yingshan fi raphy analyzed and reinterpreted, plus additional con dential Formation) (Figs. 3 and 4). The transitional boundary between well data (CNPC China database and Sinopec China database). progradational and retrogradational reflection sequences is fi 5) Velocity data for 20 wells (5 vertical seismic pro les (VSP) and the basal boundary of the Ordovician (Gao and Fan, 2014a, Figs. 3 15 Check-shots). and 4). 6) Three outcrop measured stratigraphic sections (Fig. 2) and 45 thin sections. 3.1.2. Line 2 in Central Tarim area Interpretation of all seismic profiles has been done on Work- Line 2 (seismic profile Gu08-403) is in the Central Tarim area station HP xw 6600 by using the software of Landmark 2005, and (Figs. 1 and 2), and extends east from Tazhong Uplift to the all seismic profiles are migration profiles. Manjiaer Depression (Fig. 1). On seismic line 2 (Figs. 5 and 6), the

Fig. 2. This shows database of wells, outcrops and seismic proﬁles. 294 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306

Fig. 3. Regional seismic proﬁle Line 1 (e.g. seismic proﬁle AKK08-NWW-2, location in Figs. 1 and 2) in the Northern Tarim area.

entire Cambrian to Lower Ordovician succession thins abruptly 3.2. Well lithology data east on about shot-point 5600, with a mean two-way travel time of about 0.75 s to about 0.28 s (Figs. 5 and 6). Within the Cambro- 3.2.1. Well Ts1 in Northern Tarim area (Cambrian) Ordovician succession bracketed by the base of Cambrian and the The 6884.00e8408.40 m cored, logged and rock thin sectioned top of the Lower Ordovician, may be divided into five component interval of Well Ts1 in Line 1 (Figs. 1 and 8) displays typical subintervals. These include the Lower Cambrian, the Middle Cambrian lithologies, sedimentary facies and reef-shoals (Fig. 8; Cambrian, the Upper Cambrian, the Lower Ordovician Penglaiba Gao and Fan, 2014a). Formation, and the Lower Ordovician Yingshan Formation (Zhao Lower Cambrian strata are divided into six subintervals in Well et al., 1997; Wang, 1999, Figs. 1, 5 and 6). These subintervals Ts1 (Fig. 8; Gao and Fan, 2014a). The first subinterval is from display thickness trends similar to those characterizing the entire 8345.00 to 8408.00 m and is dolomitized as grey silty dolomite and succession as a whole (Figs. 5 and 6). As with the entire succes- light grey finely crystalline dolomite. GR (gamma ray) values range sion, subintervals are locally anomalously thicker along the east from about 15 to 35API, and Rs (resistivity) values range from about limits of the relatively thick portions of these subintervals along 300 to 1000 U m(Fig. 8). The second subinterval from 8160.00 to the west sides of imaged seismic lines (Figs. 5 and 6). Three pro- 8345.00 m is dolomitized and composed of grey, finely crystal gradational reflection sequences were observed in the Cambrian dolomite. GR values range from about 15 to 30API, and Rs values are on the seismic profile, in the Early, Middle and Upper Cambrian lower, ranging from about 30 to 400 U m(Fig. 8). The third sub- respectively (Figs. 5 and 6). Unlike the Cambrian, the Lower interval from 8093.04 to 8160.00 m and is composed of grey finely Ordovician contains four aggradational seismic reflection se- crystalline dolomite and micritic dolomite. GR values are lower and quences, two each in the Yingshan and the Penglaiba formations range from about 10 to 20API, and the Rs values range from about (Figs. 5 and 6). The transitional boundary between progradational 100 to 700 U m(Fig. 8). The fourth subinterval is from 7988.01 to and aggradational reflection sequences is also the base of the 8093.04 m and is composed of light grey sparry oolite dolomite Ordovician (Gao and Fan, 2014a, b; Figs. 5 and 6). (Dunham, 1962; Folk, 1959, 1962), medium crystalline dolomitized oolitic packstone and finely crystal dolomite (Fig. 8). The fifth 3.1.3. Line 3 in Southwestern Tarim area subinterval is 7873.00e7988.01 m and is composed of light grey On seismic Line 3 (seismic profile MGTO8-204SN) (Figs. 1 and fine-medium crystal dolomite contained sparry oolite dolomite 2), extending southwest from the Markit Slope region to the (Fig. 8). The sixth subinterval is 7792.54e7873.00 m with a similar Southwest Depression region (Fig. 1; Gao and Fan, 2014b), the lithology as the fifth subinterval, but is mainly grey finely crystal- entire Cambrian to Middle Ordovician succession thins abruptly line dolomite (Fig. 8). southwest on about shot-point 3850 from a mean two-way travel The upper five subintervals can be divided into two parts. The time of about 0.67 s to about 0.42 s (Fig. 7). The thicker Cambro- first succession consists of the first and second subintervals, and the Ordovician successions on the northeast sides of seismic lines second sequence contains third, fourth and fifth subintervals. The display a local anomalous increase in thickness at the southwest two successions all display an upward gradation from light fine limits of these thicker successions, such that the uppermost Lower crystal to medium crystal dolomite, then to oolite dolomite in an Ordovician strata display locally convex-upward, mounded and upward shoaling succession (James, 1984). vertically stacked seismic reflectors with both southwest and Middle Cambrian strata in Well Ts1 have been divided into four opposing northeast, or reverse, dips away from these limits subintervals (Fig. 8). The first subinterval is from 7701.12 to (Fig. 7). Southwestward-downlapping reflectors can be seen 7792.54 m and is composed of dolomitized grey sparry oolite immediately above the base of Cambrian, the base of Middle dolomite interbedded with laminar algal dolomite. The GR Cambrian and above the base of the Lower Ordovician Yingshan (gamma ray) curve is more variable with some spike-like oscil- Formation (Fig. 7). lations in values and ranges from 15 to 30API. The Rs (resistivity) Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 295

Fig. 4. Interpretation of the regional seismic proﬁle Line 1 (uninterpreted version in Fig. 3; location in Figs. 1 and 2), showing platform achitecture and pattern of reef-shoal development in the Cambrian-Lower Ordovician of northern Tarim Basin. Number designations represent individual intervals of reef-shoal deposits in each stratigraphic succession. 2 reef-shoals are in Lower Cambrian, 4 reef-shoals are in Middle Cambrian, 2 reef-shoals are in Upper Cambrian, 1 reef-shoal is in Lower Ordovician Penglaiba Formation, 4 reef-shoals are in Lower Ordovician Yingshan Formation.

Fig. 5. Regional seismic proﬁle Line 2 (e.g. seismic proﬁle Gu08-403, location in Figs. 1 and 2) in Central Tarim area. 296 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306

Fig. 6. Interpretation of the regional seismic proﬁle Line 2 (uninterpreted version in Fig. 5; location in Figs. 1 and 2), showing platform architecture and pattern of reef-shoal development in the Cambrian-Lower Ordovician of central Tarim Basin. Number designations represent individual intervals of reef-shoal deposits in each stratigraphic succession.

curve ranges in value from about 300 to 9100 U m(Fig. 8). The aphanocrystalline dolomite interbedded with mudstone. The GR second subinterval is from 7650.00 to 7701.12 m and is composed curve ranges in value from 10 to 25API, and the Rs curve ranges of light yellow fine-medium crystal dolomite interbedded with from 100 to 1000 U m. The fourth interval extends from 6884.00 to sparry oolite dolomite and laminar algal dolomite (Fig. 8). The 7021.00 m and is light grey finely crystalline dolomite interbedded third subinterval is from 7480.00 to 7650.00 m and is composed of with finely to coarsely crystalline dolomite (Fig. 8). The uppermost grey fine-medium crystal dolomite (Fig. 8). The fourth subinterval three subintervals (6884.00e7135.00 m) of the Upper Cambrian in is from 7401.00 to 7480.00 m and is composed of grey sparry finely well Ts1 also indicate that the water depth become deeper and its crystalline dolomite interbedded with thin layers of mudstone lithology shows the upward transition from grey finely crystalline (Fig. 8). The four subintervals (7401.00e7792.54 m) of the Middle dolomite to aphanocrystalline dolomite, and to grey siliciclastic Cambrian in well Ts1 display an upward gradation from light grey mudstone indicates a deepening-upward succession (Fig. 8). oolite dolomite to micritic dolomite, then to grey mudstone, and The cored interval from 7988.01 to 8093.04 m of the Lower show positive rhythm of lithology (a deepening-upward succes- Cambrian, and the interval from 7701.12 to 7792.54 m of the Middle sion of lithologies) (Fig. 8). The change of lithology in the Middle Cambrian in Well Ts1 are all light grey dolomite, sparry oolite Cambrian indicates the water depth become shallower than that dolomite and algal dolomite (Fig. 8). in the Lower Cambrian. The Upper Cambrian in Well Ts1 can be divided into four in- 3.2.2. Well Gc4 in Central Tarim area (Lower-Middle Ordovician) tervals (Fig. 8). The first interval extends from 7135.00 to 7401.00 m The 5500.00e6500.00 m cored, logged and rock thin sectioned and is mainly grey and light grey finely crystalline dolomite to interval of well Gc4 in Line 2 (Figs. 1 and 9) displays typical li- dolomicrite. The GR (gamma ray) curve ranges in value from about thologies of the Lower to Middle Ordovician (Fig. 9). Three 15 up to 30API units, and the Rs (resistivity) values range from 60 to component intervals have been separated within the Lower to 300 U m. The uppermost part of this interval is black glauconitic Middle Ordovician in Well Gc4 (Fig. 8). These include the Middle dolomite, whereas the lower part is mudstone-bearing dolomite Ordovician Yijianfang Formation, the Lower Ordovician Yingshan (i.e dolomite containing siliciclastic clay and silt) (Fig. 8). The sec- Formation and the Lower Ordovician Penglaiba Formation. ond interval, from 7098.00 to 7135.00 m, is mainly light grey finely The interval from 6250.00 to 6500.00 m in Well Gc4 (Fig. 9)is crystal dolomite. GR curve values range from 10 to 20API and are within the Lower Ordovician Penglaiba Formation. These strata are lower than in the underlying interval whereas the Rs curve displays mainly sparry intraclastic grainstone, interbedded with thin layers more elevated values ranging from 300 to 1000 U m. The third of dolomite and micritic limestone (Fig. 9). The GR curve displays interval extends from 7021.00 to 7098.00 m and is mainly light grey greater values than and is more oscillatory. Carbonate platform Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 297

Fig. 7. Regional seismic prolife Line 3 (e.g. seismic proﬁle MGTO8-204SN, location in Figs. 1 and 2) in Southwestern Tarim area, showing platform architecture and pattern of reef- shoal development in the Cambrian-Lower Ordovician of southwest Tarim Basin.

marginal shoals were well developed in the Lower Ordovician upward change in lithology is consistent with deposition as water Penglaiba Formation (Fig. 9). depth increased. Platform marginal bioherm mound and bioclastic The interval from 5610.00 to 6250.00 m in Well Gc4 (Fig. 9)is shoal deposits are common in the lower interval (Fig.10). The upper the Lower Ordovician Yingshan Formation, and is formed of two interval is comprised of three subdivisions. Every subdivision is distinct successions. The lower succession is mainly intraclastic dominantly grey organic framestone or bafﬂestone capped with a grainstone whereas the overlying succession is mainly laminar layer of light grey bioclastic grainstone. Flora and fauna in this in- algal limestone and micritic limestone. Carbonate mounds were terval include branched red and green alga, platy red alga and well developed in the upper succession, whereas reef-shoals sponges, Syringopora and tetradium corals, echinoderms, and sol- developed well in the lower succession of the Lower Ordovician enoporid alga (Fig. 10). Platform marginal reef deposits are well Yingshan Formation (Fig. 9). The GR curve values are lower and the developed in the upper interval. GR curve itself is smoother in the Yingshan Formation than that in GR values of the upper interval are lower, and its RD and RS the underlying Penglaiba Formation (Fig. 9). values are higher, than those in the lower interval. Carbonate The interval from 5500.00 to 5610.00 m in Well Gc4 (Fig. 9)is platform marginal reefs were well developed in the upper subin- the Middle Ordovician Yijianfang Formation. These strata are terval whereas moundeshoals developed well in the lower subin- mainly sparry grainstone. Grain types include intraclastic, oolite, terval of the Upper Ordovician Yijianfang Formation (Fig. 10). bioclastic and algal reef. Carbonate platform marginal reef-shoal deposits are well developed in the Middle Ordovician Yijianfang 4. Results and discussions Formation (Fig. 9). 4.1. Platform margin types 3.2.3. Well Z2 in Central Tarim area (Upper Ordovician) The 5518.00e5526.00 m cored interval of well Z2 in Central The Cambrian and Ordovician are the main carbonate succes- Tarim area (Figs. 1 and 10) displays typical Upper Ordovician li- sions in the Tarim Basin. Affected by regional dynamics, paleo- thologies and sedimentary facies, such as reef-shoal deposits depth, relative sea level change and carbonate sedimentation rate (Fig. 10). The Upper Ordovician in Well Z2 may be divided into two (Henry and George, 1977; Pigram et al., 1989; Shen et al., 2008), the intervals, an upper interval extending from 5518.00 to 5522.50 m geometry, lateral extent and disposition of lithofacies of platform and a lower interval extending from 5522.50 to 5526.00 m margin slope strata vary during Cambrian and Ordovician time respectively. (Gao et al., 2006b, 2012). Regional seismic and well data correlation The lower interval displays an upward gradation from grey shows that the Cambro-Ordovician platform margins of the Tarim bioclastic lime packstone to grey bioclastic wackestone. This Basin contain six distinctive architectures and include: (a) a 298 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306

Fig. 8. Geophysical logs and lithofacies description of a cored interval of Cambrian strata from Well Ts1, in the Northern Tarim area of Tarim basin.

progradational carbonate ramp platform; (b) a progradational here in the Yingshan Formation (Figs. 3 and 4). carbonate rimmed platform; (c) a retrogradational rimmed plat- An aggradational rimmed platform is developed in the Lower form; (d) an aggradational rimmed platform; (e) an aggradational Ordovician of the Central Tarim area (Figs. 5, 6 and 11d). Two ag- margin on an isolated carbonate platform; (f) a retrogradational gradational depositional sequences are developed in the Lower margin on a submerged carbonate platform (Fig. 11; Saller et al., Ordovician Penglaiba Formation, and two aggradational deposi- 1989; Kenter and Campbell, 1991; Pomar et al., 1996; Eberli et al., tional sequences occur in the Lower Ordovician Yingshan Forma- 2004; Playton et al., 2010; Santantonio et al., 2013). tion in the Central Tarim area (Figs. 5 and 6). On seismic line 2 A progradational carbonate ramp platform developed during (Figs. 5 and 6), the entire Lower Ordovician succession thins the Early Cambrian time in the Northern Tarim area (Figs. 3, 4 and abruptly, from a mean two-way travel time of about 0.50 s to about 11a) and during the Early to Middle Cambrian in the Southwestern 0.15 s, eastward from the rimmed margin position (about shot- Tarim area (Figs. 7 and 11a). Two progradational ramp-type depo- point 5600; Figs. 5 and 6). sitional sequence tracts, developed in the Lower Cambrian of the An aggradational margin on an isolated carbonate platform Northern Tarim area, extend southeast from the Northern Tarim (Blendinger, 1986) developed during the early Late Ordovician Uplift to the Manjiaer Depression (Figs. 3, 4 and 11a). Two pro- deposition (Fig. 11e, see Line7 in Fig. 14) followed by development gradational reflectors are prominent in the Lower Cambrian, and of a retrogradational margin on a submerged carbonate platform four progradational reflectors can be seen in the Middle Cambrian (Menier et al., 2014) during later Late Ordovician deposition of the in the Southwestern Tarim area (Figs. 7 and 11a). These prograda- Sangtamu Formation (Fig. 11f, see Line4 and Line6 in Figs. 1 and 14). tional reflectors extend southwest from the Markit Slope to the Carbonate platform margins are volumetrically significant parts Southwest Depression (Figs. 1, 2 and 7). of carbonate platforms and contain stratigraphic records which A progradational carbonate rimmed platform can be seen in the reflect the growth, evolution, and depositional conditions of the Middle Cambrian of the Northern Tarim area (Figs. 3, 4 and 11b). carbonate system (Cook and Mullins, 1983; Coniglio and Dix, 1992; Four progradational depositional sequences are developed in the Playton et al., 2010). Stratal architecture and lap terminations of Middle Cambrian of the Northern Tarim area (Figs. 3 and 4). platform margins based on actual outcrop and subsurface are A retrogradational rimmed platform occurs in the Lower extensively clarified in different sedimentary basin, and variations Ordovician Yingshan Formation in the Northern Tarim Area (Figs. 3, in margin configuration, clinoform shape and downlap pattern are 4 and 11c). Four retrogradational depositional sequences developed analyzed (Saller et al., 1989; Kenter and Campbell, 1991; Pomar Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 299

Fig. 9. Geophysical logs and lithofacies description of a cored interval of Lower Ordovician strata from Well Gc4, in the eastern of Central Tarim area.

et al., 1996; Adams and Schlager, 2000; Playton et al., 2010; Eberli whereas there are no similar margins in Tarim Bain. et al., 2004). Prograding margins with sigmoidal clinoforms are developed in Miocene-modern, Leeward, GBB, Bahamas (Eberli 4.2. Reef-shoals et al., 2004), which are similar to the progradational carbonate ramp platform in Tarim Basin (Fig. 11a). Prograding margins with Carbonates sediments, and carbonate platform structure types exponential clinoforms and climbing downlap are developed in were determined by water depth, temperature, salinity, and hy- Miocene, Mallorca, Spain (Pomar et al., 1996), which are similar to drodynamic conditions (Pigram et al., 1989; McNeill, 2005; Gao the progradational carbonate rimmed platform in Tarim Basin et al., 2006). Affected by regional tectonic movements and rela- (Fig. 11b). Retrograding margins with exponential clinoforms are tive sea level change, a variety of carbonate platform types are identified in Lower Jurassic, Atlas, Morocco (Kenter and Campbell, developed at the same time across different parts of Tarim basin 1991), which are similar to the retrogradational rimmed carbon- (Fig. 11). ate platform in Tarim Basin (Fig. 11c). Aggrading margins with parallel clinoforms are discovered in Lower-Middle Permian, Texas 4.2.1. Reef-shoals - Northern Tarim area (Saller et al., 1989), which are similar to the aggradational rimmed The temporal changes in platform development are also re- carbonate platform in Tarim Basin (Fig. 11d). Platform margins with flected in reef-shoal reservoir variations (Gao and Fan, 2014a). In accretionary to escarpment transition and relief-building on flat the Early Cambrian, the platform in the Northern Tarim area was a surface are identified in Upper Devonian, Western Australia carbonate ramp. However, relative sea level began to rise during (Playton et al., 2010), which are similar to the aggradational margin the Early Ordovician, and the platform changed to a rimmed on an isolated carbonate platform and the retrogradational margin margin-type. Such changes of platform style controlled the distri- on a submerged carbonate platform in Tarim Basin (Fig.11e and f). It bution of the platform margin and the development of a reef-shoal is rare that six types of carbonate platform margins are developed complex. Influenced by the platform style, the Cambrian reef-shoal in the same basin, but no every platform margin types are all complex was progradational, whereas the Early Ordovician reef- developed in Tarim basin. The prograding margins with planar shoal complex was retrogradational, as seen on seismic lines clinoforms and sub-horizontal downlap are developed in Upper (Figs. 3 and 4). There were eight reef-shoal complexes in the Permian, Texas (Adams and Schlager, 2000; Playton et al., 2010), Cambrian (two in the Lower Cambrian, four in the Middle Cambrian 300 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306

Fig. 10. Geophysical logs and lithofacies description of a cored interval of Upper Ordovician strata from Well Z2, in the southern of Central Tarim area.

Fig. 11. Platform margin types in the Cambrian-Ordovician of Tarim basin. (a) a progradational carbonate ramp platform; (b) a progradational carbonate rimmed platform; (c) a retrogradational rimmed carbonateplatform; (d) an aggradational rimmed carbonate platform; (e) an aggradational margin on an isolated carbonate platform; (f) a retrogradational margin on a submerged carbonate platform. and two in the Upper Cambrian). characteristics of the Cambrian reef-shoals (Fig. 8). The cored in- The 6884.00e8408.40 m cored and rock thin sectioned interval terval from 7988.01 to 8093.04 m in Well Ts1 (Fig. 8) is Lower of well Ts1 in Line 3 (Figs. 4 and 8) displays the development Cambrian, and is composed of light grey dolomite and algal Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 301

Fig. 12. Paleosedimentologic elements during deposition of Early Cambrian Xiaoerbulake Formation, in Tarim Basin.

Fig. 13. Paleosedimentologic elements during deposition of Early Ordovician Penglaiba Formation, in Tarim Basin. 302 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306

Fig. 14. Paleosedimentologic elements during deposition of Late Ordovician Penglaiba Formation, in Tarim Basin.

dolomite. The cored interval from 7701.12 to 7792.54 m in Well Ts1 migrated basinward and developed a progradational reef-shoal (Fig. 8) is Middle Cambrian, and is composed of light grey dolomite, complex (Figs. 3 and 4). sparry oolite dolomite and algal dolomite. Carbonate mounds were During deposition of the Lower Ordovician Penglaiba Formation well developed in the Lower Cambrian whereas reef-shoals and Yingshan Formation, the platform margin slope moved pro- developed well in the Middle Cambrian (Fig. 8). gressively towards the platform, indicating relatively rapid sea level Due to erosion, only two reef-shoal complex deposits are pre- rise. Reef-shoal complexes that formed during this time were ret- served in the Upper Cambrian. There are five reef-shoal complexes rogradational (Figs. 3 and 4). Reef-shoal complexes mainly devel- preserved of which one is in the Lower Ordovician Penglaiba oped along slope breaks whereas carbonate slumps formed on the Formation and the other four are in the Lower Ordovician Ying- slope, and intra-platform shoals developed within the platform. shan Formation (Figs. 1e4). There are five progradational deposi- Some reef-shoal bodies overlap and form multiple reef-shoal tional sequences from the base of the Lower Cambrian that complexes. Along the platform margin slope, different stages of become slightly more aggradational in the Middle Cambrian than reef masses overlap each other, i.e. the younger reefs onlap the in the Lower Cambrian. Each of these represents a complete older reefs. Reef-shoals on the marginal slope are stacked and transgressive-regressive depositional sequence. During deposition appear to have developed continuously, whereas reef-shoals within of these sequences there appears to be a progressive change from a the platform are mostly isolated. weakly rimmed platform to a more strongly rimmed platform (Fig. 4). The thin Lowermost Ordovician succession beneath the 4.2.2. Reef-shoals - Central Tarim area Yingshan is a dominantly strongly regressive sequence tract (with The Cambrian platformal succession in the Central Tarim area is a thin, perhaps seismically-unidentifiable, basal transgressive similar to that in the Northern Tarim area. However, the Lower sequence tract just above the top of “Cambrian”) with a low Ordovician reef-shoal complex shows an aggradational in the amplitude weakly-rimmed shoal platform edge. This was followed Central Tarim area, rather than a retrogradational style of platform by deposition of a retrogradational reef-shoal complex, or trans- edge development (Figs. 1, 2, 5 and 6). gressive sequence tract through to the end of the Early Ordovician The three separate reef-shoal complexes in the Cambrian of the (Figs. 3 and 4). Central Tarim show a progradational style in seismic lines (Fig. 6). 0 The unconformity T8 (basal boundary of the Ordovician) is the Individual complexes occur in the Lower, Middle, and Upper transitional boundary between progradational and retrograda- Cambrian respectively. In the Lower Ordovician, four reef-shoal tional reef-shoal complexes. Reef-shoal complexes mainly devel- complexes developed on the platform margin forming two shoal oped along the platform margin and migrated along with it. The deposits in the Yingshan Formation, and two in the Penglaiba seismic and well data indicate that the Northern Tarim area was Formation. The 5500.00e6500.00 m cored, logged and rock thin dominated by regressive, progradational depositional sequence sectioned interval of well Gc4 in Line 2 (Figs. 1 and 9) displays the tracts in the Cambrian. The platform marginal slope belt gradually Lower to Middle Ordovician lithologies and sedimentary facies, Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 303 which are consistent with reef-shoal deposition (Fig. 9) in the Two areas of Cambrian platform margin-slope deposits, sepa- Central Tarim area. rated by open shelf deposits, are accumulated in the northern and The interval from 6250.00 to 6500.00 m of the Lower Ordovician southern parts of Tarim basin: Along the sections of well Yq6ewell Penglaiba Formation in Well Gc4 (Fig. 9) is composed mainly of Ts1ewell At22ewell Yw2ewell Tz34ewell Tz27ewell Tc1ewell sparry intraclastic grainstone with thin interbeds of dolomite and Mac1ewell Yb1ewell Psb2ewell Tac2ewell T1, a convex micritic limestone (Fig. 9) consistent with carbonate platform southward-facing platform margin-slope developed surrounding marginal shoal deposition. The Lower Ordovician Yingshan For- the larger northern platform (Fig. 12). The segment of the platform mation, from 5610.00 to 6250.00 m in Well Gc4 (Fig. 9), can be margin-slope in the Northern Tarim area is steepest, whereas divided into two intervals. Carbonate mounds were well developed margin-slope segments in the Central Tarim and in the South- during deposition of the upper interval, whereas reef-shoal depo- western Tarim area are progressively less steep. The line1, line2, sition was dominant in the lower interval of this formation (Fig. 9). line3 and Well Ts1 in Fig. 12 which show the Cambrian platform The interval from 5500.00 to 5610.00 m of the Middle Ordovi- margin characteristics (Figs. 4, 6e8). The cored interval from cian Yijianfang Formation in Well Gc4 is mainly sparry grainstone 7988.01 to 8093.04 m of the Lower Cambrian, and the interval from and algal reef, consistent with carbonate platform marginal reef- 7701.12 to 7792.54 m of the Middle Cambrian in Well Ts1 are all 0 shoal deposition (Fig. 9). The unconformity T8 (base of the Ordo- light grey dolomite, sparry oolite dolomite and algal dolomite vician) approximately coincides with a transitional boundary be- (Fig. 8). These sedimentary facies in the Lower-Middle Cambrian tween progradational and aggradational styles of reef-shoal indicates that platform marginal reef-shoals were abundant during deposition. The Early to Middle Cambrian platform was a subma- the Early-Middle Cambrian in the vicinity of in Well Ts1 (Fig. 8). A rine ramp with an indistinct platform edge with continuous well- second, shorter southern platform margin-slope extends along a developed seismic reflectors and with some onlapping reflections trend including wells Sz1 and Mic1 in a convex northwestward- at the slope, whereas the Early Ordovician platform had a well- shaped belt around the smaller southern platform (Fig. 12). developed rimmed margin with reef buildups (Fig. 6). Open platform and restricted platform facies deposits are Late Ordovician was the time of maximum reef-shoal develop- extensive across the western and central portion of the northern ment during the entire Cambro-Ordovician. The 5518.00e5526.00 m platform inboard of the slope belt, whereas shallow marine shelf cored interval of the Lianglitage Formation in well Z2 in the Central facies and basin facies deposits are developed east and south of the Tarim area displays the development characteristics of the Upper slope belt (Fig. 12). Dolomite and limestone are widespread in the Ordovician reef-shoals (Figs. 1 and 10). The 5522.50e5526.00 m middle and western parts of the Tarim Basin, especially across most interval displays an upward gradation from packstone to wackstone of the Central Tarim, Bachu and Northern Tarim uplifts, displaying with bioclastic (Dunham, 1962; Folk, 1959, 1962), and shows the evidence of platform facies (e.g. Well H4 and Outcrop PLB, Fig. 12). characteristics of platform marginal mound and bioclastic shoal. This Dolomite can be seen in the Lower Cambrian in Well H4 (e.g. Well indicates that carbonate margin shoals were well developed in the H4, Fig. 12) and represent restricted platform facies, and algal early Late Ordovician whereas reefs developed well in the late Late dolomite and bioturbated limestone can be seen in the Lower Ordovician (Fig. 10). However, the 5518.00e5522.50 m interval is Cambrian in Outcrop PLB (e.g. Outcrop PLB, Fig. 12) and show the comprised of grey coralline and algal framestone or bafflestone characteristics of open platform facies. At the same time, intra- capped with a layer of light grey grainstone containing bioclastic platform shoals were developed mainly in the middle and west- material (Fig. 10), which is more characteristic of platform marginal ern parts of Tarim Basin. reefs. During this period, mudstone and shale occupy the eastern parts of Tarim Basin, especially across Manjiaer depression, and are 4.2.3. Reef-shoals - Southwestern Tarim area indicative of basinal deposition (e.g. Well Wl1, Fig. 12). Siliceous The Cambrian platform succession in the Southwestern Tarim mudstone and shale in the Lower Cambrian of Well Wl1 are typical area is similar to that in the Central Tarim area, and the Lower basinal deposits of this area (e.g. Well Wl1, Fig. 12). Ordovician platform succession in the Southwestern Tarim area resembles that in the Northern Tarim area (Gao and Fan, 2014b). 4.3.2. Platform margin and reef-shoals - Early Ordovician However, the scale of reef-shoal development in the Southwestern The sedimentary framework of the Early Ordovician is similar to Tarim is smaller than that of the Northern Tarim and Central Tarim that of the Early Cambrian (Gao and Fan, 2014a). However, some areas. The Southwestern Tarim reef-shoal complex shows a pro- areas underwent sedimentary facies changes as a result of later gradational style in the Cambrian, and a retrogradational style in tectonic movements and sea level variations (Gao et al., 2006; Feng the Lower Ordovician (Figs. 1, 2 and 7). Three progradational reef- et al., 2007). The two key sedimentary characteristics of the Tarim shoal complexes are developed in the Cambrian with individual Basin in the Early Ordovician are the development of the Awati complexes in the Lower Cambrian, the Middle Cambrian and the (northwestern Tarim) trough and widespread development of Upper Cambrian (Fig. 7). In Early Ordovician time, two reef-shoal platform shoals (Fig. 13). The Awati trough is a small U-shaped complexes developed along the platform margin, one in the Ying- trough of slope and basinal deposition that developed within the shan Formation and the other in the Penglaiba Formation. The reef- northwestern part of the northern platform, which developed shoal complexes in the Early Ordovician Yingshan Formation show previously in Cambrian time and continued into Early Ordovician a weakly retrogradation style in seismic profile (Fig. 7). time. This basinal trough opened to the northwest through an area including Outcrop WS, Well Ab1, and Well F1 in the Awati 4.3. Platform margin and reef-shoals - Cambro-Ordovician depression (Figs. 1 and 13). The presence of the Awati trough is inferred by the black Lower Ordovician siliceous shale and 4.3.1. Platform margin and reef-shoals - Early Cambrian mudstone in Outcrop WS (e.g. Outcrop WS, Fig. 13). A progradational ramp-type platform margin of low deposi- By late Early Ordovician the marginal slope began to change tional dip is developed in the Lower Cambrian of Tarim basin with a position gradually (Gao and Fan, 2014b) through the southward slightly steeper platform margin-slope and some carbonate flux- migration of the Southwestern Tarim slope (Figs. 2 and 13), as well oturbidite slope deposits in the Northern Tarim area (Figs. 1, 4 and as the eastward migration of the western slope of the Manjiaer 8). Carbonate mounds and shoal deposits are common whereas reef depression (Eastern Tarim depression, Figs. 2 and 13). This trans- masses are rare in the ramp-type Tarim platform margin (Fig. 8). formed the previous northern Lower Cambrian platform margin- 304 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 slope into a larger southward-facing platform margin-slope belt, formed mainly platform margin reef deposits of gray/light gray, which extends through well Kn1, well Mc1, well Gc4, well Tg1, well organic framestone (Embry and Klovan, 1971; Scholle and Ulmer- Tc1, well Yb1, and Outcrop KDLK (Fig. 13). The line1, line2, line3 and Scholle, 2003) or bafflestone with alga, sponge and coral (e.g. Well Gc4 in Fig. 13 which show the Lower Ordovician platform Well Z2, Fig. 10, Fig. 14; Zamparelli and Zuhlke, 2005). The Well Z2 margin characteristics (Figs. 4, 6, 7 and 9). Compared with the in Fig. 14 which show the lithology characteristics of the Upper Cambrian, the Early Ordovician platform margin-slopes became Ordovician platform margin (Fig. 10). narrower and steeper, and migrated basinward (cf. Figs. 12 and 13). In Lower Ordovician, the Southwestern Tarim slope and the west- 5. Conclusions ern slope of the Manjiaer depression are still separated by open shelf deposits. Black shale and mudstone can be seen in the Lower Platform size and shape changed throughout the early Palae- Ordovician in Outcrop KDLK (e.g. Outcrop KDLK, Fig. 13) and ozoic in Tarim basin. The architecture and type of platform margin represent open shelf deposits. controlled the distribution of facies and the development of reef- The area covered by platform facies expanded in the Early shoals. Ordovician, and the widespread platform facies in the west changed dramatically to an open platform across a large area (1) Six types of carbonate platform marginal slope have been containing many intra-platform shoals. Platform shoals were identified in the Cambrian-Ordovician in Tarim basin. These mostly intraclastic shoals composed of gray/light gray, sparry cal- include a progradational carbonate ramp platform, a pro- carenite, lime mudstone, limestone, dolomitic limestone, or lime- gradational carbonate rimmed platform, an aggradational stone with a gravel-sized grain content of more than 50% (Gao and rimmed carbonate platform, a retrogradational rimmed Fan, 2013; e.g. Well Gl1, Figs. 10 and 13). Limestone and dolomitic carbonate platform, an aggradational margin on an isolated limestone in the Lower Ordovician of Well Gl1 are typical open carbonate platform and a retrogradational margin on a platform deposits (e.g. Well WG1, Fig. 13). The calcite cement is submerged carbonate platform. mostly microcrystalline or spar. Relative changes in sea level are not (2) Various platform margin architectures and reef-shoal char- readily apparent within the platform succession, and the deposi- acteristics are developed within Tarim basin. In the Northern tional stacking pattern of intra-platform shoals was mainly Tarim area, a progradational carbonate ramp platform accretionary. margin developed in the Early Cambrian, a slightly progradational rimmed carbonate platform margin developed in 4.3.3. Platform margin and reef-shoals - Late Ordovician the Middle-Late Cambrian time, and a retrogradational In the Late Ordovician, fault block differentiation in the Tarim rimmed carbonate platform margin developed in the Early Basin became more pronounced, due to increasing compression Ordovician time. In the Central Tarim area, a progradational (Gao and Fan, 2014a). Upthrust fault blocks formed subaqueous carbonate ramp platform margin developed in the Early- uplifts whereas downthrown fault blocks became hemipelagic or Middle Cambrian, a slightly progradational rimmed plat- abyssal basins and received thick clastic turbidite deposits, which form margin developed in the Late Cambrian, and finally followed a large-scale transgression in the Late Ordovician (Gao became an aggradational rimmed platform margin by the et al., 2006a, b). Transgression began early in the Late Ordovician Early Ordovician time. In the Southwestern Tarim area, a and formed a shelf seaway that divided the western platform into progradational carbonate ramp platform margin in Cambrian two parts. In the Awati and Hadexun areas, thick continental shelf time became a retrogradational to aggradational rimmed sediments were deposited, separating the previously linked the platform margin by the Early Ordovician time. Northern Tarim-Central Tarim Platform into two isolated islands, (3) Platform margin-slopes migrated throughout the Cambro- the Northern Tarim and Central Tarim Platforms (Fig. 14). The inset Ordovician. The broad platform area (west Tarim Platform) line 4, line5 and line6 in Fig. 14 which show platform margin that occupied most of northwestern and central Tarim Basin characteristic of the Central Tarim Platform (Fig. 14). During the in Early Cambrian time was split by an east-west oriented Late Ordovician, the Tangnan Platform was developed to a relatively shelf seaway that began to develop along the eastern and narrow, elongate west-to-east, area that faced a large region of western margins of the platform in Early Ordovician time hemipelagic and abyssal deposition in the eastern half of Tarim and completely transected the platform by Late Ordovician Basin (Fig. 14). The inset line 7 in Fig. 14 which show one of the time. The resultant central Tarim Basin platform area was contractional faults that bounds Tangnan Platform (Fig. 14; Gomez much reduced, elongate east-west around the Central Tarim and Fernandez-Lopez, 2006). Smaller platform areas bordering the paleo-uplift, and terminated eastward towards region of Late north and south sides of Tarim Basin were separated from the Ordovician basinal deposition across the eastern Tarim Basin. central platform by open shelf seaways (Fig. 14). During this period, the Tangnan slope still girdled the Tangnan platform (e.g. Seismic profile Line7, Fig. 14). The Northern Tarim Foundation item slope developed as a semicircle around the Northern Tarim Plat- form by Late Ordovician time, whereas the northern, east-facing, Supported by National Natural Science Foundation of China marginal slope of the Central Tarim Uplift changed from north- (Grant Nos. 41102087), National “973” program (Grant Nos. south trending in the early Early Cambrian to a more angled “L”- 2012CB214802), Major National Sci-Tech Projects (Grant Nos. shape in the late Early Ordovician, and, finally, in the Late Ordovi- 2011ZX05005-002-010HZ, 2011ZX05009-002) and the Funda- cian to more east-west trend around the Central Tarim paleo-uplift mental Research Funds for the Central Universities (2-9-2012-091). (e.g. Seismic profiles Line 4 and Line 5, Fig. 14). The southern marginal slope of the Central Tarim Uplift changed from east-west Acknowledgements trending to north-south trending at Well M4 from Cambrian to Late Ordovician time. The southern and northern platform margins of Thanks are due to Profs Qian Yixiong, Drs. Jiao Zhifeng and David the Central Tarim Uplift are a weakly retrogradation margin (James, Morrow for constructive comments and language revision. We are 1984; e.g. seismic profiles Line 4 and Line 6, Fig. 14). Reef-shoals also grateful to Prof. Kang Zhi-hong and Dr Zhao Hanting, Yu Wenyi, were extensively developed along these platform margins, and Wang Qiuchun, Li Ning for help during field work. This research is Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306 305 supported by National Natural Science Foundation of China (Grant carbonate platform. J. Palaeogeogr. 11 (1), 21e27. No. 41102087), National 973 program of China (Grant No. Gu, Z.D., Wang, Z.C., Hu, S.Y., Wang, H., Yin, J.F., Huang, P.H., 2012. Tectonic settings of global Marine carbonate giant Fields and exploration significance. Nat. Gas. 2012CB214802), and Major National Science-Technology Projects of Geosci. 23 (1), 106e117. China (Grant Nos. 2011ZX05005-002-010HZ, 2011ZX05009-002 Halbouty, M.T., 2003. Giant oil and gas fields of the 1990s: an introduction. In: e and 2011ZX05005-004-HZ06), and Fundamental Research Funds Halbouty, M.T., et al. (Eds.), Giant Oil and Gas Fields of the Decade 1990 1999, American Association of Petroleum Geologists Memoir 78, pp. 1e13. for the Central Universities. Han, J.F., Sun, C.H., Yu, H.F., Ji, Y.G., Zhang, Z.H., Xu, Y.L., 2011. Kinetics of reef-shoal complexes and its restriction to reservoir in Ordovician from Central Tarim I fault belt. Acta Petrol. Sin. 27 (3), 845e856. References Heldt, M., Lehmann, J., Bachmann, M., Negra, H., Kuss, J., 2010. Increased terrigenous influx but no drowning: palaeoenvironmental evolution of the tunisian car- Adams, E.W., Schlager, W., 2000. Basin types of submarine slope curvature. bonate platform margin during the Late Aptian. Sedimentology 57, 695e719. J. Sediment. Res. 70, 814e828. Henry, T.M., George, W.L., 1977. Origin of the northwestern Bahama platform: re- Blendinger, W., 1986. Isolated stationary carbonate platforms: the Middle Triassic view and reinterpretation. Geol. Soc. Am. Bull. 88, 447e1461. (Ladinian) of the Marmolada area, Dolomites, Italy. Sedimentology 33, 159e183. Hu, J.Z., Ran, Q.G., Liu, S.G., Sun, W., Wang, D., Zhang, C.J., 2009. Sedimentary facies Castro, J.M., Gea, G.A., Ruiz-Ortiz, P.A., Nieto, L.M., 2008. Development of carbonate analysis of Cambrian-Ordovician in eastern Tarim Basin. Lithol. Reserv. 21 (2), platforms on an extensional (rifted) margin: the Valanginian-Albian record of 70e75. the Prebetic of Alicante (SE Spain). Cretac. Res. 29, 848e860. James, N.P., 1984. Shallowing-upward sequences in carbonates. In: Walker, R.G. Coniglio, M., Dix, G.R., 1992. Carbonate slope. In: Walker, R.G., James, N.P. (Eds.), (Ed.), Facies Models: Geological Association of Canada. Geoscience Canada, Facies Models: Response to Sea Level Change. Geological Association of Canada, Reprint Series 1, pp. 213e228. Geoscience Canada Series, pp. 349e374. Jiang, H.Y., Song, X.M., Wang, Y.J., 2008. Current situation and forecast of the world’s Cook, H.E., Mullins, H.T., 1983. Basin margin environment. In: Scholle, P.A., carbonate oil and gas exploration and development. Offshore Oil 28 (4), 6e13. Bebout, D.G., Moore, C.H. (Eds.), Carbonate Depositional Environments, Amer- Jiao, Y.Q., Rong, H., Wang, R., Wu, L.Q., Yan, J.X., Zeng, F.P., Gu, Y., Li, R., 2011. ican Association of Petroleum Geologists Memoir 33, pp. 539e618. Reservoir depositional system analysis of ordovician carbonate platform margin Dunham, R.J., 1962. Classification of carbonate rocks according to depositional in Yijianfang outcrops of western Tarim Basin. Acta Petrol. Sin. 27 (1), 285e296. texture. In: Ham, W.E. (Ed.), Classification of Carbonate Rocks:, American As- Jin, Z.J., Yun, J.B., Zhou, B., 2009. Types and characteristics of slope zones in Tarim sociation of Petroleum Geologists Memoir, pp. 108e121. Basin and their relationship with oil accumulation. Oil Gas Geol. 30 (2), Eberli, G.P., Ginsburg, R.N., 1989. Cenozoic progradation of northwestern Great 127e135. Bahama Bank, a record of lateral platform growth and sea-level fluctuations. In: Kang, Y.Z., 1985. Discovery of high-yield oil-gas flow in well Shacan2 and explo- Crevello, P.D., Wilson, J.L., Sarg, J.F., Read, J.F. (Eds.), Controls on Carbonate ration direction in Tarim Basin in future. Oil Gas Geoloy 6, 21e25. Platforms and Basin Development. Special Publication-sepm 44, pp. 339e351. Kenter, J.A.M., 1990. Carbonate platform flanks: slope angle and sediment fabric. Eberli, G.P., Anselmetti, F.S., Betzler, C., Van Konijnenburg, J.H., Bernoulli, D., 2004. Sedimentology 37, 777e794. Carbonate platform to basin transitions on seismic data and in outcrops: Great Kenter, J.A.M., Campbell, A.E., 1991. Sedimentation on a lower Jurassic carbonate Bahama Bank and the Maiella Platform margin, Italy. In: Eberli, G.P., platform flank: geometry, sediment fabric and related depositional structures Masaferro, J.L., Sarg, J.F. (Eds.), Seismic Imaging of Carbonate Reservoirs and (Djebel Bou Dahar, High Atlas, Morocco). Sediment. Geol. 72, 1e34. Systems:, American Association of Petroleum Geologists Memoir 81, Kenter, J.A.M., Harrisb, P.M., Porta, G.D., 2005. Steep microbial boundstone- pp. 207e250. dominated platform margins: examples and implications. Sediment. Geol. Embry, A.F., Klovan, J.E., 1971. A late devonian reef tract on Northeastern Banks 178, 5e30. island, N. W. T. Can. Pet. Geol. Bull. 19, 730e781. Kong, Q.Y., Cheng, R.H., 2010. Sedimentary characteristics of cambrian-lower Fan, T.L., 1998. Superposition patterns of condensed sections and its relation to sea- ordovician sequence in peacock river area in Tarim Basin, Xinjiang, NW level changes in paleozoic of North Tarim Basin. Acta Geosci. Sin. 19 (3), China. J. Jilin Univ. Sci. Ed. 40 (3), 527e534. 308e314. Menier, D., Pierson, B., Chalabi, A., Ting, K.K., Pubellier, M., 2014. Morphological Fan, T.L., Yu, B.S., Gao, Z.Q., 2007. Characteristics of carbonate sequence stratigraphy indicators of structural control, relative sea-level fluctuations and platform and its control on oil gas in Tarim Basin. Geoscience 21 (1), 57e65. drowning on present-day and miocene carbonate platforms. Mar. Petroleum Feng, Z.Z., Bao, Z.D., Wu, M.B., Jin, Z.K., Shi, X.Z., 2006. Lithofacies palaeogeography Geol. 58, 776e788. of the Cambrian in Tarim area. J. Palaeogeogr. 8 (4), 427e439. McNeill, D.F., 2005. Accumulation rates from well-dated late neogene carbonate Feng, Z.Z., Bao, Z.D., Wu, M.B., Jin, Z.K., Shi, X.Z., Luo, A.R., 2007. Lithofacies palae- platforms and margins. Sediment. Geol. 175, 73e87. ogeography of the ordovician in Tarim area. J. Palaeogeogr. 9 (5), 447e460. Pan, W.Q., Wang, Z.M., Sun, C.H., Li, B.H., Ren, K.X., Han, J., Jiang, H., Yuan, S.Q., 2011. Folk, R.L., 1959. Practical petrographic classification of limestones. Am. Assoc. Pe- Classifications of sequence boundaries in the lower paleozoie carbonates in troleum Geol. Bull. 43, 1e38. Tarim Basin and their significances. Oil Gas Geol. 32 (4), 531e540. Folk, R.L., 1962. Spectral subdivision of limestone types. In: Ham, W.E. (Ed.), Clas- Phelps, R.M., Kerans, C., Loucks, R.G., Dagama, R.O.B.P., Jeremiah, J., Hull, D., 2014. sification of Carbonate Rocks-a Symposium:, American Association of Petro- Oceanographic and eustatic control of carbonate platform evolution and leum Geologists Memoir 1, pp. 62e84. sequence stratigraphy on the cretaceous (ValanginianeCampanian) passive Gao, Z.Q., Fan, T.L., Wang, H.M., 2005. The developmental conditions and distribu- margin, northern Gulf of Mexico. Sedimentology 61, 461e496. tional rules of the reef-shoal reservoirs in Central Tarim Basin. Xinjiang Geol. 23 Pigram, C.J., Davies, P.J., Feary, D.A., 1989. Tectonic controls on carbonate platform (3), 283e287. evolution in southern Papua New Guinea: passive margin to foreland basin. Gao, Z.Q., Fan, T.L., Li, Y., 2006a. Study on eustatic sea-level change rule in Cambrian Geology 17, 199e202. Ordovician in Tarim Basin. J. Jilin Univ. Sci. Ed. 36 (4), 549e556. Playton, T.E., Janson, X., Kerans, C., 2010. Carbonate slopes. In: James, N.P., Gao, Z.Q., Fan, T.L., Jiao, Z.F., Li, Y., 2006b. The structural types and depositional Dalrymple, R.W. (Eds.), Facies Models 4. Geological Association of Canada, characteristics of carbonate platform in the Cambrian-Ordovician of Tarim Ba- pp. 449e476. Part ThreeeChemical and Biochemical Facies Models, number 15. sin. Acta Sedmentologica Sin. 24 (1), 19e27. Pomar, L., Ward, W.C., Green, D.G., 1996. Upper miocene reef complex of the Liuc- Gao, Z.Q., Fan, T.L., Yang, W.H., Wang, X., 2011. Distribution characteristics of major area, Mallorca, Spain. In: Franseen, E., Esteban, M., Ward, W.C., Eopaleozoic platform edge slope in southwestern Tarim Basin. J. Central South Rouchy, J.M. (Eds.), Models for Carbonate Stratigraphy from Miocene Reef Univ. 42 (12), 3811e3817. Complexes of the Mediterranean Regions, SEPM Concepts in Sedimentology Gao, Z.Q., Fan, T.L., Wang, X., Yang, W.H., 2012. Structure characteristics and evo- and Paleotology Series 5, pp. 191e225. lution of the Eopaleozoic Carbonate Platform in Tarim Basin. J. Jilin Univ. Earth Pomar, L., Gili, E., Obrador, A., Ward, W.C., 2005. Facies structure and high- Sci. Ed. 42 (3), 657e665. resolution sequence stratigraphy of an upper Cretaceous platform margin Gao, Z.Q., Fan, T.L., 2013. Ordovician intra-platform shoal reservoirs in the Tarim succession, southern central Pyrenees, Spain. Sediment. Geol. 175, 339e365. Basin, NW China: characteristics and depositional controls. Bull. Can. Petroleum Saller, A.H., Barton, J.W., Barton, R.E., 1989. Slope sedimentation associated with a Geol. 61 (1), 83e100. vertically building shelf Bone Spring formation, Mescalero Escarpe Fields, Gao, Z.Q., Fan, T.L., 2014a. Intra-platform tectono-sedimentary response to geo- southeastern New Mexico. In: Crevelb, P.D., Wilson, J.L., Sarg, J.F., et al. (Eds.), dynamic transition along the margin of the Tarim Basin, NW China. J. Asian Controls on Carbonate Platform and Basin Development. SEPM Special Publi- Earth Sci. 96, 178e193. cation 44, pp. 275e288. Gao, Z.Q., Fan, T.L., 2014b. An early Paleozoic inter-platform shelf in the Southwest Santantonio, M., Scrocca, D., Lipparini, L., 2013. The Ombrina-Rospo Plateau (Apu- of Tarim Basin, NW China and its significance for petroleum exploration. Resour. lian platform): evolution of a carbonate platform and its margins during the Geol. 64 (4), 346e366. jurassic and cretaceous. Mar. Petroleum Geol. 42, 4e29. Gomez, J.J., Fernandez-Lopez, S.R., 2006. The Iberian Middle Jurassic carbonate- Schlager, W., Camber, O., 1986. Submarine slope angles, drowning unconformities, platform system: synthesis of the palaeogeographic elements of its eastern and self-erosion of limestone escarpments. Geology 14, 762e765. margin (Spain). Palaeogeogr. Palaeoclimatol. Palaeoecol. 236, 190e205. Schlager, W., Reijmer, J.J.G., Droxler, A.W., 1994. Highstand shedding of carbonat Graziano, R., 2000. The Aptian-Albian of the Apulia carbonate platform (Gargano platforms. J. Sediment. Res. Sect. Stratigr. Glob. Stud. 64, 270e281. Promontory, southern Italy): evidence of palaeoceanographic and tectonic Scholle, P.A., Ulmer-Scholle, D.S., 2003. A Color Guide to the Petrography of Car- controls on the stratigraphic architecture of the platform margin. Cretac. Res. bonate Rocks. In: American Association of Petroleum Geologists Memoir 77, 21, 107e126. p. 474. Gu, J.Y., Ma, F., Ji, L.D., 2009. Types, characteristics and main controlling factors of Scott, R.W., 1993. Cretaceous carbonate platform, U.S. Gulf Coast. In: Simo, T.J.A., 306 Z. Gao, T. Fan / Marine and Petroleum Geology 68 (2015) 291e306

Scott, R.W., Masse, J.-P. (Eds.), Cretaceous Carbonate Platforms, American As- Yu, K.H., Jin, Z.K., 2011. Application of seismic facies analysis method in studies of sociation of Petroleum Geologists Memoir 56, pp. 97e109. evolution and characteristics of Gucheng platform in Tarim Basin. Nat. Gas. Shen, J.W., Webb, G.E., Jell, J.S., 2008. Platform margins, reef facies, and microbial Geosci. 22 (1), 115e121. carbonates; a comparison of Devonian reef complexes in the Canning Basin, Zamparelli, V.E.A., Zuhlke, R.B.T., 2005. The reefal margin and slope of a Middle Western Australia, and the Guilin region, South China. Earth Sci. Rev. 88, 33e59. Triassic carbonate platform: the Latemar (Dolomites, Italy). Facies 50, 573e614. Sun, X.L., 2011. Endeavour to ten million tons of oil and gas fields. China Petrochem. Zhao, Z.X., Yong, T.S., Jia, C.Z., 1997. Stratigraphic Units in the Tarim Basin. Petroleum 3, 32e33. Industry Press, Beijing, pp. 1e65. Wang, Y., 1999. Sequence stratigraphy of the Sinian-middle devonian system in the Zhang, G.Y., Zhao, W.Z., Wang, H.J., 2007. Multicycle tectonic evolution and com- Tarim Basin. Acta Sedmentologica Sin. 17 (3), 414e421. posite petroleum systems in the Tarim Basin. Oil Gas Geol. 28 (5), 653e662. Wang, Z.M., Zhang, L.J., Wang, Z.Y., Han, J.F., Liu, Y.H., Shen, A.J., 2007. Features of Zhang, Z.S., Liu, S.P., 1995. Sequence stratigaphy analysis of carbonate series of lower ordovician reef Beach and exploration activities in Tarim Basin. Pet. Geol. 6, 1e7. Palaeozoic group in the Tarim Basin. Oil Geophys. Prospect. 30 (2), 245e256. Yang, H.J., Zhu, G.Y., Han, J.F., Wu, F.F., Ji, Y.G., Su, J., Zhang, H.Z., Wang, Y., 2011. Zheng, S.Q., Liu, D., Liu, Z.C., Kang, Z.J., 2015. Well controlled Reserve calculation for Conditions and mechanism of hydrocarbon accumulation in large reef-bank fractured-Vuggy carbonate reservoirs in tahe Oilfield, Tarim Basin. Xinjiang Pet. karst oil/gas fields of Central Tarim area, Tarim Basin. Acta Petrol. Sin. 27 (6), Geol. 36 (1), 78e81. 1865e1885.