Mega arrowhead interference patterns in the central part of the Yanshan Orogenic Belt,North China |
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| Institution: | 1. School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia;2. Instituto Geonorte, National University of Salta, INENCO-CONICET, Av. Bolivia 5150, 4400, Salta, Argentina;3. Centre for Lithospheric Research, Czech Geological Survey, Klárov 3, 118 21, Prague 1, Czech Republic;1. Dipartimento di Scienze della Terra, Università di Napoli Federico II, Naples, Italy;2. Dipartimento di Scienze della Terra e dell''Ambiente, Università di Pavia, Via Ferrata, 1, Pavia, Italy;1. School of Marine Sciences, Sun Yat-sen University, Zhuhai 519082, China;2. School of Geological Engineering and Geomatics, Chang''an University, Xi''an 710054, China;3. Department of Earth Science, University of Bergen, Allegt. 41, 5007 Bergen, Norway;4. Guangdong University Key Laboratory of Offshore Oil Exploration and Development /Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China;5. Regional Geological Surveying Party of the Tibet Bureau of Geology and Exploration, Lhasa 851400, China;6. Southern Laboratory of Ocean Science and Engineering (Zhuhai, Guangdong), Zhuhai 519000, China;1. DiSTeM – Dipartimento di Scienze della Terra e del Mare, Università di Palermo, via Archirafi 22, 90123 Palermo, Italy;2. Istituto Nazionale di Geofisica e Vulcanologia, sez. di Palermo, via Ugo la Malfa 153, 90146 Palermo, Italy;3. Exploro AS, Jarlbsborgveien 8, 7041 Trondheim, Norway |
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| Abstract: | The Chengde-Pingquan region is located in the central part of the Yanshan Orogenic Belt (YOB). At Daheishan and Pingquan in the central YOB, thrusts and folds of variable trends are displayed in 2 km-scale fold interference patterns. Detailed field mapping was conducted to decipher the geometry of these two superimposed structures. Map-view geometry and stereonet plots for outcrop-scale folds indicate that the superimposed structures form arrowhead interference pattern where NW-SE-trending F1 folds are refolded by later ENE-WSW F2 folding. After remove the effects of later faulting, restored map-views of the superimposed structures show that when the F1 folds have inclined axial surfaces but with no an overturned limb, an arrowhead interference pattern (here called modified type-2 pattern) can form. Our field data and reinterpretation of the findings of previous studies suggest that five major shortening phases have occurred in the Chengde-Pingquan region. The first two phases, which formed the superimposed folds, occurred earlier than the Late Triassic (D1) and during the Late Triassic to Early Jurassic (D2). These two phases were followed by three deformation phases that are mainly characterized by thrusting and strike-slip faulting, which strongly modified the large-scale fold interference patterns. |
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| Keywords: | Fold interference patterns Arrowhead The Yanshan Orogenic Belt Kilometer scale |
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