CAJ | 학술논문

指示天然气水合物存在的重要地球物理标志---BSR（似海底反射）在南海北部陆坡晚中新世以来的地层中广泛分布。根据BSR在晚中新世以来3个三级层序地层内的分布特点，结合区域热动力背景、沉积特征（沉积相、沉积速率、含砂率、岩性特征等）和典型沉积体（构造坡折带、滑塌体、沉积物波）的综合分析，系统研究了南海北部陆坡天然气水合物的沉积成藏特征。研究表明， BSR的分布在满足温压、气源的基础上更明显地受沉积体系展布和所处构造部位的控制，气源和温压条件只是影响BSR分布的必要条件而非充分条件。建立了南海北部陆坡典型沉积成藏模式，总结了在陆架、陆坡、陆基上随着水深的增加各种沉积体的分布及其与BSR和水合物稳定带的关系，展示了水合物成藏的典型要素。BSR与构造坡折、深水重力流及等深流沉积密切相关，大多数BSR分布区均位于地貌变化陡峭、地形起伏较大、长期继承性隆升与沉降交汇的黏土质粉砂和粉砂等沉积物中。在陆架三角洲前缘，BSR侧向较连续但延伸距离短，水合物成藏的关键在于深部气源的沟通条件；在陆坡海槽与底辟发育区，BSR受断层与底辟切割往往呈断续分布，沉积物的快速卸载可为水合物的赋存提供较好的沉积储层条件；在陆基至深海区海底扇、浊流、等深流发育的位置，BSR侧向连续延伸距离远，气源主要为浅部生物气，以侧向运移为主。
지시천연기수합물존재적중요지구물리표지---BSR（사해저반사）재남해북부륙파만중신세이래적지층중엄범분포。근거BSR재만중신세이래3개삼급층서지층내적분포특점，결합구역열동력배경、침적특정（침적상、침적속솔、함사솔、암성특정등）화전형침적체（구조파절대、활탑체、침적물파）적종합분석，계통연구료남해북부륙파천연기수합물적침적성장특정。연구표명， BSR적분포재만족온압、기원적기출상경명현지수침적체계전포화소처구조부위적공제，기원화온압조건지시영향BSR분포적필요조건이비충분조건。건립료남해북부륙파전형침적성장모식，총결료재륙가、륙파、륙기상수착수심적증가각충침적체적분포급기여BSR화수합물은정대적관계，전시료수합물성장적전형요소。BSR여구조파절、심수중력류급등심류침적밀절상관，대다수BSR분포구균위우지모변화두초、지형기복교대、장기계승성륭승여침강교회적점토질분사화분사등침적물중。재륙가삼각주전연，BSR측향교련속단연신거리단，수합물성장적관건재우심부기원적구통조건；재륙파해조여저벽발육구，BSR수단층여저벽절할왕왕정단속분포，침적물적쾌속사재가위수합물적부존제공교호적침적저층조건；재륙기지심해구해저선、탁류、등심류발육적위치，BSR측향련속연신거리원，기원주요위천부생물기，이측향운이위주。
Bottom simulating reflections (BSR)are important geophysical markers of gas hydrate and widely present in the northern con-tinental slope of South China Sea (SCS)since the late Miocene.In this study,we systematically analyze the depositional accumulationcharacteristics of gas hydrate in the northern continental slope of SCS in accordance with the distribution pattern of BSR in three third-or-der sequence stratum since the late Miocene,and combined with an integrated study of regional thermodynamic background as well asthe depositional conditions (depositional facies,depositional rate,sand content,and lithology)and typical depositional bodies (structuralslope,slumping block,and sediment waves).Under preferential conditions of temperature,pressure and gas source,the distribution ofBSR is obviously constricted by the expansion of depositional system and the background of geological structure.That is,temperature,pressure,and gas source are necessary rather than sufficient conditions for the distribution of BSR.Following the above findings,a typi-cal depositional accumulation model for the northern continental slope of SCS is established.The proposed model summarizes the dis-tribution of depositional systems in continental structures (shelf,slope,and rise)with increasing water depth and their relationshipwith BSR and gas hydrate stability zones,displaying the typical elements of gas hydrate accumulation.The presence of BSR is close-ly related to structural slope break zones,deep-water gravity flow,and contourites.The majority of BSR are distributed in clay siltand silt deposits in seaward areas with steep and rough relief and long-term successive uplift and subsidence.In the frontier of conti-nental shelf,BSR are laterally continuous but extend in a short distance,where the key of gas hydrate accumulation lies in the trans-port conditions for deep gas source.In the slope-trough and diapir development zones,BSR show discontinuous distribution as divid-ed by faults and diapirs,where rapid unloading of deposits provides preferential depositional accumulation conditions for gas hydrate.In the continental rise to deep-sea areas with the development of submarine fans,turbidity currents and contour currents,BSR arelaterally continuous and extends in a long distance with shallow biogas as the major source and mainly through lateral mitigation.