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脱水淫羊藿素同系物治疗男性勃起功能障碍的临床观察
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勃起功能障碍(ED)是指过去3个月中,阴茎持续不能达到和维持足够的勃起以进行满意的性生活[1]。据国际流行病学调查勃起功能障碍的发病率占成年男性的50%左右,娴岁以上男性中、重度ED的发病率为5.0%,70岁的发病率为15.0%[2]。国内冷静等[3]的流行病学调查显示,ED发病率随年龄增加而上升,40~49岁年龄组勃起功能障碍为32.8%,而到70岁以上年龄组达86.3%。ED严重影响患者的生活质量。笔者从淫羊藿和苦参中提取的脱水淫羊藿素同系物作为有效组分配伍[4]制成AHI同系物制剂,治疗中老年中度男性功能性ED取得满意疗效,现将观察结果报道如下。1资料与方法1.1临床资料选取年龄在50~70岁,病程大于6个月,勃起功能积分(IIEF-5)在8.0-11.0分的中度功能ED患者,并排除高血压、糖尿病、冠b病、心脑血管意外,脊髓损伤等合并疾病的门诊患者20例。将患者随机分为治疗组和对照组。其中治疗组1O例给予AHI化合物治疗(25Mg/次,1次/d,每晚睡前服用,连续口服6个月),对照组1O例给予枸橼酸西删阳巨治疗(25mg/次,1次/d,每晚睡前服用,连续口服6个月)。两组患者在年龄、病程、病情程度及勃起功能积分方面比较无显著瞬(P&0.05),具有可比性。1.2统计学方法所有数据采用SPSS10.0进行统计分析。1.3药物与含量测定枸橼酸西地那非片(国药准字H2002O528,辉瑞制药有限公司,批号1083011);注射用前列腺素El(国药准字H,北京泰德制药有限公司,批号2117S);AHI同系物来源朝鲜淫羊藿(Emedium&brea-num)和苦参(淄博康华中药公司)各100KG,粉碎后用60%的乙醇固定(固-液比为12:1),再经80℃回90min,提取三次,过滤,水溶部分依次用石油醚(60~80℃),二氯甲烷,乙酸乙酯和正丁醇萃取,分别回收溶剂。乙酸乙酯部分经硅胶柱分离[5],得AHI化合物0.68mg/kg。使用高效液相色谱与电喷雾质谱联用技术(HPLC-ESI)测定AⅢ同系物,保留时间(tR&68.8min,分子离子峰铌9,源内CD质谱数据536和371。1.4疗效标准与治疗结果1.4.1疗效标准按照国际勃起功能评分问卷(IIEF-5)≤21分诊断为ED;治愈:治疗后性交机会达75%以上成功,或勃起功能积分≥21分;显效:治疗后性交机会达50%以上成功,或勃起功能积分较前增加7,0~14.0分;有效:治疗后性交机会达笏%以上成功,或勃起功能积分较前增加(7分;无效:治疗后性交机会成功率无变化,或勃起功能积分无增加。1.4.2夜问阴茎肿胀试验用进口纸带进行,连续测量6个夜晚,在患者睡眠良好时,红、黄、蓝3纸带全部断裂为正常勃起;红、黄、蓝3纸带全未断裂为夜间无勃起;仅红色断裂为无效勃起;黄、蓝2条纸带断裂为勃起不充分。并使用阴茎硬度测试仪夜间多次测试,判断标准为正常:强度≥1OO、持续时间≥10min、勃起次数≥6;轻度异常:强度BO~1O0、持续时间≥10min、勃起次数≥6;中度异常:强度40~8O(持续时间&10min、勃起次数(6;重度异常:强度(硐、持续时间、勃起次数)。1.4.3阴茎海绵体注射血管活性药物试验(ICI)直接将血管活性物质注进阴茎海绵体内,诱发勃起,从诱发勃起的时间、硬度、勃起角度、持续时间来判定阴茎的血流供给和静脉回流情况。注射药物:前列腺素E110~40ug。患者自行注射后15min,勃起角度,维持勃起时间&15min,为ICI阳性(正常);勃起角度&60°,维持勃起时间不足30min,而且不能进行性交,注射2次以上仍无改善为ICI阴性。1.4.4彩色双功能超声检查(CDU)是一种无创伤性检查,高频探头可观察阴茎有无病理性改变,4.5MHz脉冲测距探头可进行血流分析,测定血流率,结合观察注射前后阴茎血流情况,了解阴茎动脉血供和静脉闭合机制。主要参数有:动脉收缩期最大血流流率为阴茎动脉血供正常。2结果2.1治疗有效率提高参照国际ED诊断原则进行ⅡEF-5评分发现,治疗组、对照组在治疗后平均勃起功能积分分别比治疗前增加了8.7分和9.2分。治疗组lO例,显效6例,有效3例,无效1例,总有效率为⒇,0%;对照组10例,显效7例,有效2例,无效1例。数据显示,治疗组、对照组在治疗后平均血流流率分别为阴茎动脉血供正常。两组比较,治疗组疗效与对照组疗效无显著性差异(P&0.05)。见表1。2.2治疗后勃起强度、持续时间有改善根据NPT诊断标准,使用阴茎硬度测试仪对ED患者进行治疗前后测试,数据显示:治疗组、对照组在治疗后平均夜间勃起强度分别比治疗前增加了贸。7和58,9;平均勃起持续时间增加了15.9min和19.2min;平均勃起频率增加了3.4次和3.6次;平均总勃起时间增加了120.3min和154,9min;膨胀均大于2~75px。两组数据比较无显著性差异(P&0.05)。见表2。3讨论HI同系物成分推测应包含淫羊藿有效成分淫羊藿苷的代谢产物:脱水淫羊藿素和去甲基脱水淫羊藿素[6]。而苦参中也应包含异脱水淫羊藿素和降脱水淫羊藿素[7],其具体成分和含量有待进一步验证。笔者观察到淫羊藿苷对试验兔阴茎海绵体、阴蒂海绵体组织内.胆有浓度依赖增高效应[刚。试验结果也表明,经过KHl同系物治疗ED与枸橼酸西地那非治疗效果相当,勃起阳性率提高90%,每周性生活平均1次以上的患者由治疗前的0例(0.0%)上升到9例(90.0%),给患者的勃起带来了质的变化,也给患者带来很好的性生活满意度。'本研究还发现,患者在服用AHI同系物后,除性功能改善外,体能也有明显改善,几乎所有患者用药后都自觉精力提高,但至今未见相关的文献报道。现代中药学配伍已经不再是传统意义上按照病情和药性将两种以上中药配合使用或者是按照君臣佐使的法度加以组合确定,而是采用标准提取物配伍、中药有效组分配伍[9]和有效成分同系物配伍。其中中药有效成分同系物配伍,不但遵循中药传统配伍理论的整合起效的特点,而且符合中医的配伍理论,又符合现代医学病理、药理理论,目前虽处于理论研究阶段,但为中药客观化、直观化以及国际化和标准化提供了依据,也为有效成分的配伍使用奠定了基础。参考文献[1]NH&Consensus&Conterence.Importance&NH&consensus&development&panel&on&impotence[J].Journal&of&the&American&Medical&Association,-90.[2]Feldman&HA,Goldstein&I,Hatzichristou&DG.Impotence&and&psychosocial&correlates:results&of&the&Massachusetts&male&aging&study[J].The&Journal&of&Urology,-61.[3]冷静,王益鑫,黄旭元.上海市1582例中老年男子勃起功能障碍流行病学调查[J].中国男科学杂志,-31.[4]苗明三,马霄,王灿.中药有效组分配伍研究的探讨[J].中药新药与临床药理,7-490.[5]李文魁,潘景歧,张如意.脱水淫羊藿素-3-O-苷类化合物的核磁共振谱研究[J].波谱学杂志,1-296.[6]德冈康雄.小檗科植物的化学研究[J].日本药学杂志,.[7]张吕浩,白龙义明,李镐.苦参化学成分研究[J].延边大学医学学报,8-270.[8]刘武江,辛钟成,付杰.淫羊藿苷对去势大鼠阴茎海绵体一氧化氮合酶亚型mRNA和蛋白表达的影响[J].中国药理学通报,5-649.[9]刘新军,苏式兵.中药及其成分配伍组方的研究方法探析[J].中西医结合学报,-46.&
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淘豆网网友近日为您收集整理了关于Miocene-to-recent-structure-and-basinal-architecture-along-the-Central-Range-strike-slip-fault-zone,-eastern-offshore-Trinidad的文档，希望对您的工作和学习有所帮助。以下是文档介绍：Miocene-to-recent-structure-and-basinal-architecture-along-the-Central-Range-strike-slip-fault-zone,-eastern-offshore-Trinidad Miocene-to-recent structure and basinal architecture along the Central Rangestrike-slip fault zone, eastern offshore TrinidadDavid Soto a,1, Paul Mann a,*, Alejandro Escalona baUniversity of Texas Institute for Geophysics, Jackson School of Geosciences, J.J. Pickle Research Campus, 10100
Road, Bldg. 196 [R2200], Austin, TX , USAbUniversity of Stavanger, Depart(来源：淘豆网[/p-7346646.html])ment of Petroleum Engineering, 4036 Stavanger, Norwaya r t i c l e i n f oArticle history:Received 6 November 2008Received in revised form25 June epted 26 July 2010Available online 4 August 2010Keywords:CaribbeanTrinidadOrinoco deltaStrike-slip faultingTranspressionDarien ridgeSubsidencea b s t r a c tPrevious GPS-based geodetic studies and onland paleoseismologic studies in Trinidad have shown thatthe 50-km-long, linear, onland segment of the Centr(来源：淘豆网[/p-7346646.html])al Range fault zone (CRFZ) modates at least60% of the total rate of right-lateral displacement (w20 mm/yr) between the Caribbean and SouthAmerican plates. 2D and 3D seismic reection data from a 60-km-long and 30-km-wide swath of theeastern shelf of Trinidad (block 2AB) were used to map the eastern offshore extension of this potentiallyseismogenic and hazardous fault system and to document its deeper structure and tectonic controls onmiddle Miocene t(来源：淘豆网[/p-7346646.html])o recent clastic stratigraphy. Two unconformity surfaces and seaoor were mappedusing 3D seismic data to generate isochron maps and to illustrate the close control of the CRFZ andassociated secondary faults on small, clastic basins formed along its anastomosing strands and the east-west-striking North Darien Ridge fault zone (NDRFZ) that exhibits a down-to-the-north normal throw.Mapped surfaces include: 1) the middle Miocene angular unconformity, a p(来源：淘豆网[/p-7346646.html])rominent, regional uncon-formity surface separating underlying thrust-deformed rocks from a much less defor this regional unconformity is well studied from onland outcrops in Trinidad and in otheroffshore areas around T 2) a Late Neogene angular unconformity developed locally within block2AB that is not recognized in T and 3) the seaoor of the eastern Trinidad shelf which exhibitslinear scarps for both the CRFZ a(来源：淘豆网[/p-7346646.html])nd the east-west-striking North Darien Ridge fault zone. Clastic sedi-mentary ll patterns identied on these isochron maps indicate bined effect of strike-slip andreverse faulting (i.e., tectonic transpression) produced by active right-lateral shear on the CRFZ, which isconsistent with the obliquity of the strike of the fault to the interplate slip vector known from GPSstudies in onland Trinidad. The NDRFZ and a sub-parallel and linear family of east(来源：淘豆网[/p-7346646.html])-west-striking faultswith normal and possibly transtensional motions also contributed to the creation of modationspace within localized, post-middle Miocene clastic depocenters south of the CRFZ. 2010 Elsevier Ltd. All rights reserved.1. Introduction and objectivesThe island of Trinidad is the easternmost land area of an elon-gate fold-thrust belt which extends from eastern Venezuela and isthe result of the oblique collision and transpression betwee(来源：淘豆网[/p-7346646.html])n theCaribbean and South American plates during Neogene time (Babband Mann, 1999; Duerto and McClay, 2010) (Fig. 1). To the south-east of Trinidad, the Columbus basin is the easternmost andyoungest foreland basin developed at the presently active, easterntip of the collision zone between the Caribbean plate and thenorthern margin of South America (Wood, 2000; Garciacaro et al.,2010, a,b; Escalona and Mann, 2010). The Columbus forelandbasin formed ab(来源：淘豆网[/p-7346646.html])ove the northward-dipping South Americancontinental plate which includes a Cretaceous-early Cenozoicpassive margin sequence overlying Precambrian cratonic rocks ofthe Guyana shield (Fig. 1).The colliding Great Arc of the Caribbean that fringes much of theeastward-moving Caribbean plate includes Cretaceous and earlyCenozoic metamorphic, igneous and metasedimentary rocks ofnorthern Trinidad and Tobago (Algar and Pindell, 1993; Snoke et al.,2001), and (来源：淘豆网[/p-7346646.html])intervening, deep, fault-bounded sedimentary basinssuch as the Grenada and Tobago basins that formed as a result ofPaleogene extension of the Great Arc (Mann, 1999; Aitken et al.,2010) (Fig. 1). Regional GPS measurements in the Caribbean byDeMets et al. (2000), Perez et al. (2001), and Weber et al. (2001)have found that the Caribbean plate translates eastward (w085)with respect to the South America plate, at a rate of about* Corresponding author.E-m(来源：淘豆网[/p-7346646.html])ail address: paulm@ig.utexas.edu (P. Mann).1Present address: Repsol, Bogota, Colombia.Contents lists available at ScienceDirectMarine and Petroleum Geologyjournal homepage: ate/marpetgeo/$ e see front matter
2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.marpetgeo.Marine and Petroleum Geology 28 (420 mm/yr. The broad Barbados accretionary prism formed duringwestward subduction of oceanic crust of the Atlantic Oceanbeneath the Caribbean plate and arc system (Xie et al., 2010;Escalona and Mann, 2010) (Fig. 1).Collisional deformation of Trinidad, which culminated in a short-lived but intense period of middle Miocene folding and thrusting,was followed by a more protracted period of distributed right-lateral strike-slip faulting across the island (Robertson and Burke,1989; Erlich et al., 1993; Algar and Pindell, 1993; Babb and Mann,1999). This period of post-middle Miocene right-lateral shearingcontinues up to the present-day as seen from denser workson the island of Trinidad that indicate that 2/3 of the 20 mm/yrCaribbeandSouth American interplate motion is modated bythe Central Range fault zone (12
3 mm/yr) with less well con-strained rates of motion on the Los Bajos fault along the southernedge of the island (2 mm/yr) and the southern offshore area(6 mm/yr) (Weber et al., ; Saleh et al., 2004). Trenching ofthe CRFZ by Crosby et al. (2003) and Crosby et al. (2009) shows thefault cuts &5000-year-old sediments and is capped by w550-year-old sediment. These authors infer that the fault has ruptured at leastonce during this interval and is therefore a Holocene fault capable ofproducing damaging earthquakes in Trinidad.In our previous study of the shallow structure of the CRFZ, wehave shown that the CRFZ extends 60 km into the eastern offshoreshelf of Trinidad and dextrally offsets a shallowly-buried (83 mbelow sealevel), late Quaternary uvial channel by 322e506 m(Soto et al., 2007). We inferred a 17e19 mm/yr longterm slip rate forthe CRFZ based on the amount of offset and our inferred age of thechannel that is larger than the GPS estimate for the rate of motionacross the fault (12
3 mm/yr) by Weber et al. (2010).The geology of the 4829 km2island of Trinidad plex andnot well exposed except along coastal cliffs and manmade roadcuts,because of its humid climate and dense, tropical vegetation. Thepurpose of this study is to integrate 2D and 3D seismic reectiondata with limited well data from the 60-km-long and 30-km-widearea of exploration block 2AB on the broad shelfal area east ofTrinidad (Fig. 2). These offshore 3D seismic data allow us to expandthe virtual “outcrop area” of onland Trinidad by displaying timeslices of subsurface geology beneath an 1147 km2area of thesubmerged eastern shelf area of Trinidad e or about 23% of theexposed surface area of the island of Trinidad (Fig. 2). Unlike ourprevious study that focused only on the late Quaternary history ofsedimentation and shallow structure of the CRFZ to a depth ofabout 100 m below the seaoor of the eastern shelf (Soto et al.,2007), in this study we make use of the entire 3D seismic cubealong with a crossing regional 2D seismic line to image the faultstructure and associated basins to depths of 12 s two-way time(TWT), or several kilometers beneath the seaoor. This deeper levelof imaging allows us to constrain a much longer history back to themiddle Miocene folding and thrusting event which has beenrecognized as a major tectonic in Trinidad and surrounding offshoreareas (Erlich et al., 1993).2. Geologic setting of Trinidad and its eastern offshore area2.1. Topography of TrinidadThe topography of Trinidad can be divided into ve morphologicprovinces: three elongate ranges of structurally-uplifted hills sepa-rated by two lower-lying valleys underlain by structurally-depressedsedimentary basins. The ranges and basins are generally sub-paralleland trend east-west or northeast and slightly oblique to the GPS-determined 085 direction of Caribbean plate motion relative toSouth America (Fig. 1). From north to south the ve provincesinclude: the Northern Range, the Northern (or Caroni) basin, theCentral Range, the Southern basin and the Southern Range (Fig. 3).Fig. 1. The present-day tectonic setting of the boxed study area and Central Range fault zone (CRFZ) of on- and offshore Trinidad includes four major tectonic elements illustrated ona GEOSAT free-air gravity map of the region: 1) arc, oceanic and oceanic plateau terranes of the eastward-moving Caribbean plate that are obliquely colliding in the Trinidad area arrow shows direction and rate in mm/yr of Caribbean plate motion based on GPS 2) the Venezuela and Columbus foreland basins shown in greenshading that formed as a result of this oblique collision that youngs from west to east across the northern margin of South A 3) the Barbados accretionary prism shown ingreen shading formed by the bulldozing of mainly sedimentary rocks as the Caribbean
and 4) the undeformed passive margin of South America in thesoutheastern corner of the map and shown in green shading that has not yet been deformed by the oblique collision of the Caribbean plate. (For interpretation of the references tocolour in this gure legend, the reader is referred to the web version of this article.)D. Soto et al. / Marine and Petroleum Geology 28 (4 213The Northern Range, with a maximum elevation of 925 m abovesea level (ASL), is underlain by folded and thrusted, ne-grained LateJurassic to Late Cretaceous low-grade metamorphic rocks (Donovan,1994; Saunders, 1998) which are faulted against Late Miocene torecent sediments of the Northern basin by the right-lateral El Pilarfault zone (Kugler, 1959; Algar and Pindell, 1993; Babb and Mann,1999) (Fig. 3). The Northern basin is a synclinal sedimentary basinlled by Late Miocene to Quaternary clastic sediments (Babb andMann, 1999). Most of its modern drainage of the Northern basin isdirected west into the Gulf of Paria and may reect active tectonictilting of the island in that direction (Weber et al., 2010) (Fig. 2). Incontrast with its abrupt northern ank, the southern ank of theNorthern basin rises gradually along a gently-dipping slope to theCentral Range, the second highest range of hills (w300 m) in Trini-dad (Fig. 2). The northeast-trending Central Range consists of a ne-grained Jurassic and Cretaceous sedimentary core overlain, andfaulted against, highly deformed pre-middle Miocene clastic rocks(Fig. 3). The Central Range is cut longitudinally by the well-mappedCRFZ (Saunders, 1998; Babb and Mann, 1999; Crosby et al., ), whose slip rate is inferred from GPS-based geodetic studies(Weber et al., ) (Fig. 3, inset photo).In contrast with the Northern basin, the eastwardly-drainingand synclinal Southern basin is more irregular in topography andcontains highly deformed rocks of early Cenozoic age that underliepost-middle Miocene to recent sediments (Dyer and Cosgrove,1992) (Fig. 3). The Southern Range, the lowest range in Trinidad(w200 m), is an east-west-trending thrust-fold belt that deformsand exposes post-middle Miocene clastic rocks (Fig. 3). The LosBajos fault, a Neogene right-lateral strike-slip fault with about10 km of lateral offset, cuts across the western Southern Rangeand extends offshore parallel to the southern coast of Trinidad(Babb and Mann, 1999) (Fig. 3).2.2. Bathymetry of Trinidad’s shelvesWe constructed a detailed bathymetric map of the shelf areas ofTrinidad using a grid of data piled by the University ofTexas at Austin Bureau of Economic Geology from nautical chartsfrom the Gulf of Paria (Defense Mapping Agency (DMA), 1993) andGulf of Paria to Caroni (National Imagery and Mapping Agency(NIMA), 2001). On the bathymetric map shown on Fig. 2, the100 m depth contour represents the approximate position of theshelf-slope break.Two features are notable from this pilation.First, the eastern shelf of Trinidad dips very gently eastward to theshelf break as can be seen from the pattern of widely-spacedbathymetric contours east of Trinidad (Fig. 2). Secondly, two areasof bathymetric highs are present on the eastern shelf of Trinidad: 1)a round-shaped elevated area present in the northeast corner of theblock 2AB study area that contains two adjacent highs known asEmerald shoal (crest is w5.5 m below sea level, BSL) and Prospectorpatch (crest is w18.3 m BSL) (Defense Mapping Agency, 1993); and2) an east-northeast-trending elongate high known as the Darienridge along the southwestern edge of the study area, whose shal-lowest point forms an isolated high called Darien rock (crest isw2.3 m BSL) (Defense Mapping Agency, 1993). Superposition of thebathymetry with the subsurface data in this study shows that bothareas of highs correspond to underlying structural features: theCRFZ underlies Emerald shoal and Prospector patch in the northernpart of the study area and the Darien and Galeota anticlinal ridgesunderlie Darien rock in the southern part of the study area. Theanomalously shallow seaoor expression of both areas is suggestivethat tectonic activity is active along both the CRFZ and the Darienanticlinal ridge (Wood, 2000; Boettcher et al., 2003; Garciacaroet al., 2010).Fig. 2. Topographicebathymetric map of Trinidad region showing location of 3D seismic data used from study area in eastern offshore exploration block 2AB, shown in gray. Wellsused in the study are shown as red dots. Regional 2D seismic line 32 which passes through block 2A is shown in red and partially reproduced in Fig. 5. Topography of piled from SRTM; bathymetry piled from NIMA (2001) and DMA (1993). Highest elevations in Trinidad are in the Northern Range (w900 m ASL) with lowerelevations in the Central Range (w300 m) and Southern Range (w200 m). The 100 m-deep bathymetric contour represents the approximate position of the modern shelf-slopebreak. Bathymetric intervals on the shelf are shown at 10 m intervals while slope contours are shown at 100 m intervals. Three submarine highs (Emerald shoal, Prospector Patch,and Darien rock) are indicated in the block 2AB study area. (For interpretation of the references to colour in this gure legend, the reader is referred to the web version of thisarticle.)D. Soto et al. / Marine and Petroleum Geology 28 (42142.3. Trinidad’s onland basins and major faultsThe geology of Trinidad is grouped into the same ve physio-graphic provinces (ranges separated by synclinal basins) asdescribed above and shown on the topographic map of Fig. 2. Thestratigraphy and structure of these onland basins of Trinidad withoutcrops of mainly post-middle Miocene sedimentary rocks (Fig. 3)are useful to review prior to describing the subsurface geology ofthe eastern shelf area since both the Northern and Southern basinsproject offshore beneath our study area on the eastern shelf(Fig. 2).Several previous workers have noted that the boundariesbetween the onland ranges of Trinidad monly dened bysteeply-dipping faults that are known or inferred to have a right-lateral strike-ponent and that intervening areas betweenfaults form blocks or terranes with distinctive geologic signatures(Robertson and Burke, 1989; Erlich et al., 1993) (Fig. 4). Accordingto these authors, the geologically distinct blocks underlying theNorthern Range, Northern basin, Central Range, Southern basin,and Southern Range originated in different geographic areasalong the Caribbean-South America plate boundary and werejuxtaposed by Neogene right-lateral strike-slip fault systems(Fig. 4).Among the most important of these block-bounding strike-slipfault systems are: 1) the El Pilar fault zone, bounding the NorthernRange and the N 2) the CRFZ (whose individual faultsegments include the Warm Springs fault zone of the Gulf of Pariaand the Central RangeeCaigual fault zone of the Central Range(Babb and Mann, 1999); and 3) the Los Bajos fault, bounding thesouthern edge of the Southern Range (Fig. 3).Early structural models, such as those by Kugler (1959), Speed(1985), and Persad (1984), used widely-spaced cross sections con-structed from detailed outcrop mapping and 2D seismic lines toexplain the origin of the Central Range by a system of low-anglethrusts with mainly steep northward dips and southward tectonictransport. Alternative strike-slip tectonic models by Robertson andBurke (1989), Babb and Mann (1999), Weber et al. (2001), is et al. (2009) proposed that the Central Range formed as amore symmetrical “mega-ower structure” within a transpressivedeformational regime along a zone of anastomosing right-lateralstrike-slip prising the CRFZ. Babb and Mann (1999) alsoshow that this transpressive regime is not the only regime associ-ated with right-lateral displacement along the CRFZ. Contrary tothe onland and eastern portion of the CRFZ, these authors describetranstensional pull-apart and negative ower structures in theGulf of Paria that are also controlled by strike-slip motion on theCRFZ (Fig. 3).Following Payne (1991), they propose that the structure of theCRFZ is highly dependent on its strike with respect to the relativeplate motion directions determined by GPS studies (Weber et al.,2010). Fault segments that trend east-west or west-northwest aretranstensional while fault segments that trend northeastward arehighly transpressional. Fault character can vary abruptly over a fewkilometers provided that the fault strike changes.2.4. CretaceouseCenozoic sedimentary history of TrinidadIn order to understand the timing of formation and inlling ofTrinidad’s onland basins and their relation to major plate boundaryfaults, it is necessary to review the geologic history of the main LateFig. 3. Simplied geologic map of onshore Trinidad (modied from Saunders, 1998). The Northern Range is a fault-bounded area of JurassiceCretaceous metamorphic rocks (in darkred) correlative to those cropping out on the Araya-Paria Peninsula of Venezuela to the west. The Central Range is cored by an elongate outcrop of Cretaceous sedimentary rocks (inlight blue) faulted against pre-middle Miocene sedimentary rocks (in green). The Southern Range exposes no pre-Cenozoic rocks. The Northern basin is a synclinal basin separatingthe Northern and Central R the Southern basin is a similar, synclinal basin separating the Central and Southern Ranges. A major middle Miocene angular unconformity(dashed red line) separates highly folded and faulted pre-middle Miocene sedimentary rocks from less deformed post-middle Miocene sedimentary rocks shown in brown andyellow. Arrows show GPS vectors from Weber et al. (2001), Saleh et al. (2004) and Weber et al. (2010). Inset shows an oblique aerial view looking northeast along linear, race of the right-lateral CRFZ in the western Central Range (photo provided courtesy of C. Prentice). Location of photos shown on Fig. 4B and C are indicated. (For interpretation ofthe references to colour in this gure legend, the reader is referred to the web version of this article.)D. Soto et al. / Marine and Petroleum Geology 28 (4 215Cretaceous to recent lithologic units or formations of Trinidad. Theformations described below are colour coded by age on the geologicmap of Fig. 3 and are summarized on Table 1.During the Late Cretaceous, the region of Trinidad was thenorthern passive margin of the South American continentcontrolled by widespread, post-rift thermal subsidence thatproduced deepwater environments that included the deposition ofmudstone, blackegray shale and sandstone (Cuche Formation) anic-rich mudstone and shale (Gautier, Naparima Hill, andGuayaguayare Formation) (Erikson and Pindell, 1998; Di Croceet al., 1999) (Table 1). These rocks are mainly known from limitedoutcrops in the core of the Central Range and from deep wells in theNorthern basin and the Gulf of Paria (Erlich et al., 1993; Donovan,1994; Babb and Mann, 1999) (Fig. 4).From the Paleocene to early Miocene, the central area of Trini-dad was dominated by deepwater clastic sedimentation thatincluded shale with occasional layers of turbiditic sand derivedfrom erosion of the Precambrian Guyana shield (Chaudiere andPointe-a-Pierre Formations) (Xie et al., 2010) and monotonousmudstone with occasional sand lenses and slide blocks of olderrocks (Nariva Formation) (Fig. 4; Table 1). Erlich et al. (1993)concluded that these turbidites were deposited along foldedtroughs parallel to the Central Range and were therefore inter-preted as precursors to the folding and thrusting event thatculminated in Trinidad during the middle Miocene. According toErlich et al. (1993) early Miocene deformation was also linked toa shallowing of water depths in basins of this age.During the early Miocene the shallowing trend in the Trinidadregion reached its peak with the expansion of a deep or outer-shelfmudstone, shale and conglomerate (Brasso Formation) over wideareas of the Northern basin and Gulf of Paria (Fig. 3). Erlich et al.(1993) describe the Tamana Formation in the Central Range asa highly variable mix of coralline red algal stromatolites, algal/for-aminferal packstone and grainstone, and deepwater sand andconglomerate in which algae predominate over corals. According tothese authors, the sudden shift from clastic rocks of the BrassoFormation to carbonate sediment of the Tamana Formation marksthe termination by folding and thrusting of the long-lived passivemargin of Trinidad that had been in existence since the EarlyCretaceous (Fig. 4). The observed variety in Miocene facies is relatedto active faulting and folding controlling the sedimentation(Table 1). After the middle Miocene folding and thrusting event, it islikely that a renewed input of clastic sediments, due to theincreasing intensity of convergent deformation, terminatedcarbonate sedimentation of the Tamana Formation (Erlich et al.,1993) (Fig. 4).The entire Miocene section (Brasso, Tamana, and equivalentformations) was deformed, uplifted and, nally, exposed andtruncated by the major middle Miocene erosive event, whichsubdivided the geologic record of Trinidad in two distinctivesections: an older, highly deformed section beneath the unconfor-mity and a younger, much less deformed section above theunconformity (Fig. 4). The erosive event is marked by the distinc-tive middle Miocene angular unconformity surface (MMU) (Erlichet al., 1993) (Fig. 4). The initial uplift of the Central Range duringthe middle Miocene folding and thrusting event not only dividedthe stratigraphy of Trinidad in a vertical stratigraphic ession(Fig. 4) but also in map view by creating two independent clasticbasins (Northern and Southern) (Donovan, 1994; Erlich et al., 1993;Babb and Mann, 1999) (Fig. 4).After the middle Miocene folding and thrusting event, differentclastic units were deposited in Trinidad from source areas in thenorth and south and eventually prograded over the early topo-graphic high formed by the Central Range (Babb and Mann, 1999).Fig. 4. A) Comparison of OligoceneePleistocene stratigraphy from Northern Range, Central Range, and Southern basin and Southern Range from Erlich et al. (1993). Highlydeformed rocks underlying the middle Miocene unconformity are correlated between the Southern and Central Ranges and partially with the Northern basin. Erosion at the middleMiocene unconformity has removed the late Miocene and Pliocene section from the Central Range. Right-lateral strike-slip faults are inferred to subdivide post-middle Miocenestratigraphy of the Northern basin, Central Range, and Southern basin/Range. B) Photo of deformed marine sandstone and shale of the early and middle Miocene Brasso Formationnear town of Biche in eastern part of the Central Range that has been affected by the middle Miocene folding and thrusting event. Location of this photo and photo shown in C areshown in Fig. 3. C) Photo of tilted but unfaulted, early Pliocene Gros Morne Formation exposed in coastal cliffs at Point Radix that was deposited above the middle Mioceneunconformity and post-dated the folding and thrusting event.D. Soto et al. / Marine and Petroleum Geology 28 (4216The onlapping units on the northern ank of the Central Rangeinclude: an initial package of sandstone and siltstone (late MioceneManzanilla Formation); followed by a more open marine posed by clay and some sandstone (early Pliocene SpringvaleFormation); and nally by a sequence of sand and clay of restrictedmarine to brackish and fresh-water environments (late alparo Formation) (Robertson and Burke, 1989) (Fig. 4) (Table 1).Contemporaneous with these units (and possibly with the TamanaFormation) is an important unit of heterogeneous conglomeratedeposited along the El Pilar fault zone separating the NorthernRange and the Northern basin (late Miocene-early Pliocene CunapoFormation). The Cunapo Formation is tectonically signicantbecause it represents the rst signicant erosion of the NorthernRange and lling of the Northern basin from a northern source areaand is interpreted by Babb and Mann (1999) as recording the onsetof strike-slip motion along the El Pilar fault zone.During the Pleistocene, the Cedros Formation, the youngestformally dened unit in the stratigraphic record of Trinidad, wasdeposited across the Northern and Southern basins (Fig. 4). Thisunit posed of poorly consolidated clay and sand with lensesof conglomerate (Donovan, 1994; Erlich et al., 1993; Babb andMann, 1999) (Table 1).2.5. Three major tectonic phases in Trinidad since the ording to Babb and Mann (1999), three tectonic phases ofdeformation have controlled the basins of Trinidad since themiddle Miocene. During the rst phase, middle to late Miocene, theNorthern and the Central Range were initially uplifted due totranspression along the onshore section of the El Pilar fault zoneand along the CRFZ. In the Northern Range, the uplift and the offsetof the El Pilar fault zone generated the basal portion of theconglomeratic Cunapo Formation, while in the Central Range, theuplift along the island allowed shallow-water carbonate sedimen-tation of the Tamana Formation on structural highs producedduring the middle Miocene folding and thrusting event (Erlichet al., 1993).During the initial part of the second phase, late Miocene tomiddle Pliocene, a southward-tapering wedge of Cunapoconglomerate indicates the climax of deformation and uplift in theNorthern Range. Meanwhile, the interplate strike-slip systemexpanded south of the El Pilar fault zone to the CRFZ and the LosBajos fault zone and continued for the rest of the phase. By thisprocess the CRFZ gradually gained importance and a major pull-apart basin formed in the area of the Gulf of Paria (Babb and Mann,1999; Flinch et al., 1999).During the third and nal phase of deformation, middle o Pleistocene, southward expansion of strike-slip faults ispronounced, with the consequent expansion of the Gulf of Pariapull-apart between the El Pilar and the Warm Springs-CRFZ,shifting of the main pull-apart depocenters to the south and east(Babb and Mann, 1999), and eastward tilting of the Northern basintowards the pull-apart basin (Weber et al., 2010). is et al.(2009) note that the present-day relief of the Central Range ismost likely the result of the modern transpressional deformationpredicted by the 085 direction of plate motion acting on the west-northwest-striking CRFZ, rather than remnant topography inheri-ted from the middle Miocene thrusting event. The uplifted CentralRange and continued deltaic sedimentation from the Orinoco Riverprovide the main sources of sediments into the Gulf of Paria (Babband Mann, 1999) and on the shelf of the eastern offshore areaduring this nal phase of basin inlling (Bowman, 2003).3. Data and methodologyData used in this paper can be classied in three types:1) regional seismic data, composed of a single 2D seismic line,BOLIVAR 32, which allows the cross sectional visualization of themarg 2) detailed seismic data, composed ofa 3D seismic data volume from offshore block 2AB which allows theinterpretation of faults and surfaces in andTable 1Compilation of major sedimentary formations of Trinidad, their paleoenvironments, and tectonic settings (see text for references).Formation Stages Main lithology Environment Tectonic settingCedros Pleistocene Poorly consolidated clay to coarse-grained sand Coastal terraces Progressive progradation(from N and S) over theCentral RangeTalparo Second half of Pliocene Shales, sandy shale, sand, shale with occasional coal bed Outer shelf to nearshoreand shorelineSpringvale First half of Pliocene Fossil rich shale, with intermediate glauconitic sands asional coal layers near the topInner shelf to nearshoreManzanilla Late Miocene Fossil rich mud and sand (reservoir rocks) Brackish water to innershelfShallower-water active margin.San Jose Early Late Miocene Dark muds rich in molluscs and foraminifera Inner shelfCunapo Middle Miocene toMiddle PlioceneHeterolithic molasse with levels of shale and coals. Brackish water to innershelfTamana First half of MiddleMioceneCoralline red algae stromatolites, algal/foram packstoneand grainstone, and deepwater sand and conglomerateOuter shelf to slope, thenhigh energy shorelineand intertidal.Increase shallowing andinlling conditions.Brasso Early to rst half ofMiddle MioceneMuds, shales and silts with beds of sand andconglomeratenear the top. Correlative with part of Cipero.Outer shelf to slope Early tectonic activity in theNorthern and Central Range.Cipero Middle Oligocene toLate MioceneMuds with turbiditic sand. Last formation withoutreworked rocks.Deep water Passive margin.Nariva Middle Oligocene toEarly MioceneMonotonous muds with some sand lenses (reservoir rock)and slide blocks.Deep waterPoint-a-Pierre Early to MiddleOligoceneShales and turbiditic sand Deep waterChaudiere Paleocene Shales and turbiditic sand Deep waterGuayaguare Upper Late anic-rich muds, shales and siltstones Deep water Predominance of deepwatercalcareous sediments.Naparima Hill Middle Late anic-rich muds and shales. Some bituminouslimestone source rockAbyssalGautier Lower Late anic-rich muds, shales and sandy conglomerate. Abyssal Post-rift thermal subsidence.Cuche Upper Early Cretaceous Muds, black-gray shales and sands SlopeD. Soto et al. / Marine and Petroleum Geology 28 (4 2173) complementary data, composed of published and industrywells, which support the 2D and 3D seismic interpretation (Fig. 2).In addition to the wells, previous outcrop and subsurface studies,including Robertson and Burke (1989), Payne (1991), Erlich et al.(1993), Babb and Mann (1999), and Boettcher et al. (2003) haveall provided us with useful information that we have incorporatedinto our interpretations of the eastern offshore area.3.1. BOLIVAR 32 2D seismic he BOLIVAR 32 2D seismic line (referred to as BOL32 in thisstudy and located on Fig. 2) is a 138-km-long line acquired in May,2004, by the Institute for Geophysics at the University of Texas atAustin, as part of an NSF-funded project called BOLIVAR (Broad-band Onshore-offshore Lithosphere Investigation of Venezuela andthe Antilles Arc Region) (Fig. 5). This project recorded more than6000 km of multichannel seismic data in the southeast Caribbeanregion that is also described by Aitken et al. (2010), Garciacaro et al.(2010) and Escalona and Mann (2010). The main parameters of theBOLIVAR acquisition and processing for BOL32 are summarized onTable 2.3.2. 3D seismic survey of block 2ABThe 3D seismic data used in this study were acquired by the oilindustry in the late 1990’s over the central part of the eastern shelfof Trinidad that is immediately adjacent and oriented parallel to theeasternmost onland part of the Central Range fault zone (Soto et al.,2007) (Fig. 2). The 3D seismic survey covers an area of 1447 km2and consists of 2200 lines running northwest with mondepth point (CDP) spacing of 25 m, 2100 traces or cross linesrunning northeast with a CDP spacing of 12.5 m, and a sample rateof 4 ms (ms). The lower depth limit of the block 2AB 3D provided byindustry for this study extends only to 1200 ms of two-way traveltime (TWT), which corresponds to an approximate depth of 1170 mbelow the seaoor.3.3. Well dataWells used in this study can be classied into two categories:published wells from the general area of block 2AB and industrywells from within block 2AB (Fig. 2). The three published wells arelocated outside of block 2AB and east of BOL32 (Figs. 2 and 6). TheseFig. 5. A) Uninterpreted BOLIVAR 32 2D line extends for 138 km in a northwestesoutheast direction across the eastern offshore area of T the location of the line is shown onthe map in Fig. 2. We display on this line 12 s two-way-time (TWT) although the original line was recorded to 14 s TWT. B) Interpreted BOLIVAR 32 2D line showing the mainsubsurface structural features of the offshore area east of Trinidad. The Darien ridge (SP 1700) separates areas with different structural styles: southeast of the Darien Ridge, thedeepwater region of the southeastern Columbus foreland basin exhibits minor folding northwest of the Darien Ridge, the shelf area northeast of Trinidadexhibits major folding, thrusting, strike-slip faulting and tectonic uplift. The northwest-dipping passive margin of South America (in blue shading) is obliquely underthrusting thesouthern edge of the Darien ridge. The middle Miocene unconformity (MMU, indicated as a dashed red line) can be traced as a continuous horizon in the Darien ridge area and tothe northwest but is deeply buried and not recognizable in the Columbus foreland basin. The Central Range fault zone (CRFZ, shown as a dark blue line) is interpreted as a deeplyrooted, subvertical, strike-slip fault plane. Three wells, all located northeast of the line 32, provide age control for the horizons imaged on the line: Well N-1 (Payne, 1991) isprojected from a location 8.2 km n Emerald 2 (TTMEEI, 2003) is projected from a location 21.1 km n and Red Snapper (TTMEEI, 2003) isprojected from a location 11.8 km northeast of the line. Red rectangle on the line shows the equivalent area of the block 2AB 3D survey that is shown on the map in Fig. 2. (Forinterpretation of the references to colour in this gure legend, the reader is referred to the web version of this article.)D. Soto et al. / Marine and Petroleum Geology 28 (4218three wells include: (1) Well N1 (Payne,1991) is the shallowest wellwith a total depth (TD) of about 2837 m (BSL). Well N1 is located onthe shelf, close to the northeast corner of the 2AB 3D. (2) WellEmerald 2 (TTMEEI: Trinidad and Tobago Ministry of Energy andEnergy Industries, 2003) has a TD of 3350 m (BSL) and is locatedalso over the shelf but close to east side of the block 2AB 3D (Fig. 6).(3) Well Red Snapper (TTMEEI, 2003), the deepest well of the threewith a TD of 4335 m (BSL), is located close to the shelf breaksoutheast of the southeastern corner of the block 2AB 3D. A wellcross section showing stratigraphic correlations between all ofthree of these published wells is shown in Fig. 6.The seven industry wells are irregularly distributed within theblock 2AB 3D study area (Fig. 8, inset map). Industry well data forthis study was provided only to a depth of 457 m sub-bottom, ora depth equivalent of 450 ms TWT. A cross section over all sevenindustry wells converted to time and superimposed on a regional2D line from the 3D volume is presented in Fig. 8.3.4. MethodologyThe process of interpretation of stratigraphic and structuralfeatures in the 2D and 3D seismic was done in a coordinated andsystematic manner using Landmark Graphicssoftware. The BOL32seismic line was interpreted in the context of other BOLIVARseismic line intersections, BOL31 and 32, that were interpretedfrom other studies (Garciacaro et al., 2010; Escalona and Mann,2010). The interpretation of the block 2AB 3D itself was carriedout by interpreting crosslines, lines and horizontal time slices. Oncethe horizons were interpreted, time structure and isochron mapswere made (Figs. 9, 10 and 11). To summarize the geologic inter-pretations and identify any observable paleogeomorphic features,maps of horizontal time slices were made for specic time slices inthe manner used by Escalona and Mann (2003) and Castillo andMann (2006) (Fig. 7).Table 2Summary of acquisition parameters for BOLIVAR seismic data used in this paper.Parameter Bolivar dataVessel R/V Maurice EwingVintage 2004Source 20 gun arrayVolume: 6947 in3Streamer 6000 m active streamer480 channels at 12.5 m spacingSample rate 2 msRecord length 14 sFold 128 foldProcessing ow DemultiplexResample 4 msTrace editingBP lterDeconvolutionCDP sortingVelocity analysis and NMO correctionStackF-X time migrationArchived UTIG marine seismic data centerFig. 6. Northwestesoutheast well cross section based on published well data east of the BOL32 2D line (Fig. 2). Well N1 (Payne, 1991), located in the Northern basin, shows that thepost-middle Miocene to recent section is more than 2 km thick, and the pre-middle Miocene is less than 1 km thick. Emerald 2 (TTMEEI, 2003), located in a structurally high part ofthe Darien ridge, shows the thickest Cretaceous section. Red Snapper (TTMEEI, 2003) shows the thickest Pleistocene-recent section with more than 4 km of clastic sedimentaryrocks. This anomalous clastic sedimentary thickness records the large modation space available in the Columbus foreland basin that was produced by thrusting along theDarien ridge. Sediment was supplied by the Orinoco delta.D. Soto et al. / Marine and Petroleum Geology 28 (4 2194. Seismic data4.1. Description of features seen on regional 2D seismic he following section provides detailed descriptions for themost important seismic reection and well data used in this study,as well as the main interpretations of geology, basin architecture,and lling. The descriptions below attempt to integrate all theregional data including the BOL32 deep ration seismic line, aswell as the local 2AB block 3D dataset. Integrating the interpreta-tion of both 2D and 3D seismic data adds to the overall under-standing of the block 2AB study area (Fig. 2).4.1.1. Interpretation of BOLIVAR 32 2D seismic he BOLIVAR 32 2D seismic line (BOL32), shown uninterpretedand interpreted in Fig. 5, provides a regional perspective that helpsto place the 3D seismic data of the block 2AB area into a bettertectonic framework. The uninterpreted BOL32 (Fig. 5A) shows twostructural domains separated by faulting near shot point (SP) 1700,which corresponds to the area where the anticlinal Darien and theGaleota ridges merge in a single east-northeast-trending bathy-metric ridge (Fig. 2). Both structural domains have notable differ-ences in seismic reection and structural styles which can beassociated with their different lithologies at shallow depths andtheir different tectonic realms.South of the Darien ridge (SP 1700), in the deepwater Columbusforeland basin, continuous and strong reections can be followedup to 4 s TWT (w3900 m in depth), while discontinuous but stillclear seismic reections can be seen as deep as 8 s TWT (w7800 m)beneath SP 1300 (Fig. 5). In the shallow part of this southeast area(above 5 s TWT), large open folds are smoothly varying and exhibitlong wavelengths (about 34 km).In contrast, north of the Darien ridge (SP 1700), over thenortheast shelf area of Trinidad (area equivalent to the seaward oreastern extension of the Northern basin and Northern Range ofonland Trinidad e Fig. 2), reections are difcult to follow beyond2 s TWT, while the dip of the structures changes quickly and foldshave short and variable wavelengths (about 6 km or less).Normal growth faults were recognized on the line, despite itsunfavorable orientation sub-parallel to those faults, by consideringnortheast-trending 2D lines as interpreted by Garciacaro et al.(in this issue-a,b). This system of growth faults appears to playa critical role in the remobilization of sediments from the edge ofthe eastern shelf of Trinidad into the deep basinal environment, andconsequently contribute to the growth of the &10 km thick sedi-mentary section above Cretaceous basement. The long wavelengthfolds described above appear also to be a consequence of thenormal growth faulting as these large normal faults progressivelymobilize Neogene muds delivered by the Orinoco River from theshelf to deepwater areas (Wood, 2000; Bowman, 2003). Other foldsare produced by tectonic shortening across the Darien ridge.A pre-middle Miocene section of mobile shales is observed bySullivan et al. (2004) and Garciacaro et al. (2010) beneath theupper half of the Neogene section in the deepwater area. Thesemobile shales were initially deposited during a major Late Creta-ceous transgression over carbonate rocks of the north- andnorthwest-dipping passive margin of South America (Di Croceet al., 1999).Fig. 7. Simplied geologic map of Trinidad from Fig. 3 integrated with interpreted time slice at 400 ms TWT taken from 3D seismic data from block 2AB offshore study area. Notethe offshore continuity of the Central Range right-lateral fault (CRFZ) and localized elevation of highly deformed, fault-bounded blocks of pre-middle Miocene rocks (in greenshading to match colour of rocks of similar age from onshore Trinidad). In general, the fault block southeast of the CRFZ is depressed while the fault block northwest of the CRFZ iselevated as also observed for fault blocks southeast and northwest of the onshore CRFZ. Abbreviations of major onland and offshore faults include: AFZ
Warm S LBFZ
Central R NDRFZ
North Darien R SDRFZ
South DarienRidge fault zone. GPS vectors shown as white arrows are from Weber et al. (2001) and Weber et al. (2010). Location of the cross section based on wells in block 2AB (Fig. 6), and crosssection based on wells within block 2AB (Fig. 8) are indicated. (For interpretation of the references to colour in this gure legend, the reader is referred to the web version of thisarticle.)D. Soto et al. / Marine and Petroleum Geology 28 (4220The Cretaceous passive margin beneath the Columbus basin andDarien ridge is interpretedfromstrongbut discontinuous reectionsgoing from 6 s TWT at the southeast extreme of the line, to 8 s TWTat the center of BOL32 (Fig. 5A). The discontinuity of this reectionpackage is attributed to convergent deformation of the passivemargin section in the area beneath the Darien ridge (SP ).Convergent deformation across the Darien ridge elevates deep-marine Late Cretaceous carbonates of the passive margin probablyby a process of thrust imbrication to the surface of onland Trinidadand to shallow depths of the shelf area as documented by thepublished piled on Fig. 6 (Kugler, 1959; Saunders, 1998).The basinal area north of the Darien ridge (SP 1700) projectssouthwestward toward the northeast shelf area of Trinidad (Fig. 2). Incontrast to the southwestern area of the BOL32 line in the Columbusforeland basin, structural style in this part of the Trinidad shelf isdominated by rapid variation in shallow structures (above 2 s TWT),including short-wavelength folding, thrusting, steep faulting, andlocalized uplifts (Robertson and Burke, 1989). With the exception ofthe northern end of BOL32 (SP ) e where well imagednormal faults formed during the Paleogene opening of the Tobagobasin are apparent (Aitken et al., 2010) e most of the northern endof BOL32 is dominated by subvertical reverse faults that tend toconverge towards the center of the area (SP 2300) to form a trans-pressional “mega-ower structure” reminiscent of previouslyproposed structural interpretations of the Central Range (Babb andMann, 1999).In the core of this elongate structural high in the easternoffshore shelf area is the right-lateral strike-slip CRFZ which bisectsthe high into two parts (Fig. 5B). The position of the CRFZ, which weinterpret as a deeply rooted, subvertical fault plane, was alsoidentied using the shallow 3D seismic data in block 2AB wherethe fault system was mapped at shallow depths (Soto et al., 2007)(red rectangle on Fig. 5B).Another prominent feature visible on BOL32 in the area north ofthe Darien ridge is the middle Miocene unconformity (MMU,highlighted as a dashed red line in Fig. 5B). This angular uncon-formity can be traced as a continuous horizon across this northernarea. South of the Darien ridge in the Columbus foreland basin, thelarge thickness of Plio-Pleistocene sediments and the lack of deeperwell control make it difcult to conrm if the middle Mioceneunconformity is present at depth.4.1.2. Published well cross sections across the Darien RidgeThree published wells, located east of BOL32 (Fig. 2), were usedto build a simple geologic cross section of the Darien ridge whichis shown in Fig. 6. Well N1 (Payne, 1991), the shallowest pene-trating published well, is located on the shelf, near the northeastcorner of the 2AB 3D, in a depressed basinal area along thenortheastern offshore projection of the onshore Northern basin(Fig. 2). The area of well N1 is bounded to the north by a bathy-metric high that appears to be the eastern offshore prolongationof the Northern Range, and to the south by the prolongation of theCRFZ (Fig. 2). The logged interval of well N1 shows almost 2 km ofpost-middle Miocene to recent section, and less than 1 km ofCretaceous to pre-middle Miocene section (Fig. 6).Well Emerald 2 (TTMEEI, 2003) is located on the shelf, close tothe east side of the 2AB 3D, but on a structural high probablyproduced by folding and recent uplift along the Darien ridge. WellEmerald 2 shows about 1.5 km of post-middle Miocene to recentsection and contains the thickest Cretaceous to pre-middleMiocene section in a close grouping of three published wells drilledto a depth of about 1600 m (Fig. 6).Fig. 8. Cross section through block 2AB study area on eastern shelf of Trinidad made by correlating seven industry wells over an arbitrary seismic line taken from the block 2AB 3Dsurvey (inset shows location of wells and arbitrary seismic line). Well logs available for this area rate only a very limited thickness of the basin (w450 ms or 457 m).Stratigraphic correlations are difcult because of this narrow stratigraphic interval and the large amount of fault-controlled structural relief. Logs displayed for each well are gammarays with one log showing a normal display (0-150 API) and the other an inverted display. Biostratigraphic analyses from this logged interval show a shale-rich, outer to middle shelfsection, with occasional inuxes of deltaic and tributary sands. Sedimentary environments based on biostratigraphic analysis by colours on the wells: lig white
no data. (For interpretation of the references to colour in this gure legend, the reader is referred tothe web version of this article.)D. Soto et al. / Marine and Petroleum Geology 28 (4 221播放器加载中，请稍候...
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Miocene-to-recent-structure-and-basinal-architecture-along-the-Central-Range-strike-slip-fault-zone,-eastern-offshore-Trinidad Miocene-to-recent structure and basinal architecture along the Central Rangestrike-slip fault zone, eastern offshore TrinidadDavid Soto a,1, Paul Mann a,*, Alejandro Escalon...
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