Active Surface Salt Structures of the Western Kuqa Fold-Thrust Belt, Northwestern China
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Active surface salt structures of the western Kuqa fold-thrust belt, northwestern China Jianghai Li1, A. Alexander G. Webb2,*, Xiang Mao1, Ingrid Eckhoff2, Cindy Colón2, Kexin Zhang2, Honghao Wang1, An Li2, and Dian He2,† 1The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China 2Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA ABSTRACT fold-thrust belt display a variety of erosion- dynamics of salt motion. Although geo scientists tectonics interactions, with nuances refl ect- have interpreted thousands of salt sheets in The western Kuqa fold-thrust belt of Xin- ing the low viscosity and high erodibility of more than 35 basins worldwide (Hudec and jiang Province, China, hosts a series of surface salt, including stream defl ections, potential Jackson, 2006, 2007), subaerial preservation of salt structures. Here we present preliminary tectonic aneurysm development, and even halite salt structures is rare (Talbot and Pohjola, analysis of the geometry, kinematics, and sur- an upper-crustal test site for channel fl ow– 2009; Barnhart and Lohman, 2012). A fraction face processes of three of these structures: the focused denudation models. of these subaerial salt structures occur in active Quele open-toed salt thrust sheet, Tuzima- settings, where boundary conditions of ongoing zha salt wall, and Awate salt fountain. The INTRODUCTION deformation can be geodetically characterized. fi rst two are line-sourced, the third appears The Kuqa fold-thrust belt of Xinjiang Prov- to be point-sourced, and all are active. The Among common solid Earth materials, salt is ince, northwestern China, offers a new prospect ~35-km-long, 200-m-thick Quele open-toed distinguished by uncommonly low density, low for subaerial investigation of a range of active salt thrust sheet features internal folding, viscosity, near incompressibility, high solubil- salt structures. Because the Kuqa fold-thrust salt-lined transfer structures, dissolution ity, and high thermal expansivity. Because of belt hosts numerous gas giants and other plays topography, fl anking growth strata, and allu- these distinctive attributes, salt and salt struc- (e.g., Zhao et al., 2005), it has been explored vial fan/stream-network interactions. The tures impact a variety of research: (1) Salt is a extensively via wells, seismic refl ection, and ~10-km-long, 50-m-wide Tuzimazha salt wall strong control on the evolution and deforma- balanced palinspastic reconstruction. Over the marks a local topographic high, such that tion of many passive margin sequences, fold- past decade, this research has shown that salt fl uvial stream networks are defl ected by the thrust belts, rift basins, and interior basins (e.g., deformation controls ongoing construction of rising weak tabular salt body. The salt wall Letouzey et al., 1995; McClay et al., 2004; the fold-thrust belt (e.g., Tang et al., 2004; Wang is also fl anked by growth strata and normal Rowan and Vendeville, 2006; Warren, 2006; et al., 2011). We have initiated a new research faults. The ~2-km-long Awate salt fountain Hudec and Jackson, 2007), which are settings effort focusing on the western part of the Kuqa represents salt exhumation coincident with that host the majority of oil and gas giants fold-thrust belt where salt reaches the surface the intersection of multiple structures and a (Mann et al., 2003). (2) Salt layers make effec- in multiple structural settings. Our preliminary river. Therefore this salt body may respond tive seals in petroleum traps, and large, par- fi eld work and satellite image analysis con- to local structural and/or erosional varia- tially evacuated salt bodies are used to store a fi rm surface outcrops of active salt structures, tions, or it may play a key role determining variety of materials including hazardous waste including the salt thrust sheets, salt walls, and such variations—or both. Activity along all (Thoms and Gehle, 2000; Dribus et al., 2008). salt namakiers (“glaciers” of salt; see Talbot and three structures confi rms that active defor- (3) Salt is an analog material for studies of fl uid Pohjola, 2009). Here we provide initial geo- mation occurs from foreland to hinterland dynamics across Earth’s deep interior (Spetzler metric and kinematic characterization of these across the western Kuqa fold-thrust belt. and Anderson, 1968; Jin et al., 1994). (4) Brine structures and their relationships to erosive Gradual lateral transition from bedded fl ows, diapiric domes, and other potential salt (or processes. strata to fl ow-banded halite observed within salt-analog) structures are recognized on Venus the Quele open-toed salt thrust sheet implies and Mars, so salt studies can offer insights into GEOLOGIC BACKGROUND that similar transitions observed in seismic material fl ow and the cycling of water on planets refl ection data do not require interpreta- and moons (e.g., McKenzie et al., 1992; Mont- The Kuqa fold-thrust belt accommodates tion as diapiric cut-off relationships. The gomery et al., 2009; McEwen et al., 2011). active north-south shortening across a ~400-km- surface salt structures of the western Kuqa The diverse economic and research bene fi ts of long, ~20–65-km-wide area (Fig. 1) (Zhong salt studies highlight the importance of explor- and Xia, 1998). This belt forms a segment of *Corresponding author: [email protected] the topographic front separating the Tian Shan †Present address: Shell International Exploration ing salt occurrences at the Earth surface, where and Production Inc., 3333 Hwy 6 South, Houston, their geometries and internal structures can (i.e., Celestial Mountains) to the north from the Texas 77082, USA be directly observed and used to constrain the Tarim basin to the south. Deformation occurs Geosphere; December 2014; v. 10; no. 6; p. 1219–1234; doi:10.1130/GES01021.1; 9 fi gures. Received 29 December 2013 ♦ Revision received 18 July 2014 ♦ Accepted 4 September 2014 ♦ Published online 15 October 2014 For permission to copy, contact [email protected] 1219 © 2014 Geological Society of America Li et al. 80°20′E 80°30′E 80°40′E 80°50′E 81°00′E 81°10′E 81°20′E 81°30′E 81°40′E 81°50′E 82°00′E N k N1j 1 N1k N1k Q x N2k-Q1x E s 0 500 1000 km Junggar Basin 1 2-3 N j 44°N Q x 1 B′ 1 Q1x Q x 41° Urumqi Tianshan Mountains 1 41° 55′N Q1x 55′N Q E s Tian Shan 2 2-3 N1k J-T Q1x Kuqa fold- E s 40°N 2-3 thrust belt A′ N j 41° Fig3g-h 1 41° 50′N N k-Q x 50′N Tarim Basin 2 1 Pamir E s Baicheng Tuzimazha Salt Wall 2-3 Q1x E2-3s 72°E 80°E 88°E 36°N Q1x 41° E x K bs Fig3c-d 41° E t 2 1 45′N 1 Q2 45′N E t K1bs E x E x 1 2 2 N k-Q x N j Bozidun Salt Fountain 2 1 Q 1 N1k E x 2 Q 2 1-4 Q2 E2x E2a N2k N2k E2a N k-N j 41° N k 1 1 41° 1 N k 40′N N k 2 Baicheng synclinal basin 40′N N j 1 1 N k N j 1 Q2 N2k 1 N j Q x 1 1 N k-Q x Q x 2 1 1 E a 2 N1k N1k 41° N2k 41° 35′N Fig3c-d 35′N Q Q x 2 1 N k-Q x Awate Salt Fountain 2 1 N1j N1k E a N2k-Q1x 2 Q Q N k N1k 2 2 1 Q2 N k-N j Q2 1 1 N k N1j 2 8A Fig3a-b N j N j 41° N k N k N k-Q x N1k 1 Quilitage anticline 1 41° Q x 1 2 N k 2 1 30′N N k 1 N k 4G 1 30′N 1 2 N j Fig5 N k 1 Q 4F 1 2 Fig3e-f E s-N j 2-3 1 N j E s N j 1 2-3 - 1 N k-Q x Q x 2 1 1 Quele Open-Toed Salt Thrust 41° Q N k-Q x 41° 25′N 2 2 1 25′N N2k-Q1x N N k 2 B Q1x Q2 41° 14 km 41° 20′N A 20′N Q1x 80°20′E 80°30′E 80°40′E 80°50′E 81°00′E 81°10′E 81°20′E 81°30′E 81°40′E 81°50′E 82°00′E Q Present - Upper Pleistocene K bs Lower Bashijiqike Fm., 2 and Middle Pleistocene tillite 1 A′ sandstone, siltstone, conglomerate Quele Open-Toed Lower Pleistocene Xiyu Fm., A Q x K b Lower Cretaceous Baxigai Fm., Salt Thrust 1 conglomerate 1 mudstone with siltstone interbeds 0 0 Pliocene Kuqa Fm. Lower Cretaceous Yageliemu Fm., N2k-Q1x K y and Lower Pleistocene Xiyu Fm. 1 sandstone, siltstone, mudstone, conglomerate N k Pliocene Kuqa Fm., J-T 2 sandstone, glutenite, mudstone Jurassic-Triassic, clastic sediments 5 5 true-scale N k Miocene Kangcun Fm., km 1 sandstone, siltstone, mudstone Anticline N j Miocene Jidike Fm., glutenite, Syncline 1 mudstone, conglomerate Eocene-Oligocene Suweiyi Fm., B′ E2-3s-N1j Thrust Fault and Miocene Jidike Fm. Tuzimazha salt wall B Baicheng basin E s Eocene-Oligocene Suweiyi Fm., Buried thrust 2-3 siltstone, salt and gypsum fault 0 0 E a Oligocene Awate Fm., mudstone, Salt boundary 2 mudstone, salt, gypsum flow front 5 5 E x Eocene Xiaokuzibai Fm., Salt boundary true-scale 2 mudstone, siltstone, gypsum without flow front km Paleocene Talake Fm., 10 E1t dolomite, mudstone, conglomerate, Strike-slip fault gypsum Figure 1.