Recent analog of gypsified microbial laminites and stromatolites in solar salt works and the Miocene gypsum deposits of Saudi Arabia and Egypt

Accumulation of microbial mats and stromatolites dominate in the crystallization ponds of solar salt works west of Alexandria, Egypt. These microbial mats are laminar in the permanent submerged part of the ponds. The microbial mats commonly form sites for growth of gypsum crystals during periods having higher salinity. In the dominant submerged part of the pond, domal stromatolites are common around groundwater seepage holes. In the shallow, intermittent margin of the ponds, the laminated microbial structure forms laterally close-linked hemispheroidal stromatolite type, with unidirectional and multidirectional ripple mark-like morphology on their surface. The microbial laminite and stromatolite types in the modern solar salt works are similar to the organic-rich Miocene gypsum beds of El-Barqan (west Alexandria, Egypt) and Rabigh (north Jeddah, Saudi Arabia). The Miocene organic-rich beds consist of interlayered dark-colored microbial laminae and light-colored gypsum laminae. These beds may have three different variations: regular even lamination, laterally closed-linked hemispheroidal stromatolites, and/or discrete hemispheroidal stromatolites. Petrographic examination of the microbial laminites and stromatolites in the solar salt works and the Miocene gypsum beds indicate that the dark-colored, organic-rich laminae are composed of micritized microbial laminae and/or brown organic filaments. In El-Barqan area, the light-colored gypsum-rich laminae are composed of either gypsum crystal fragments, or lenticular and prismatic gypsum. These gypsum crystals are either entrapped within the microbial filaments or are nucleated at the surface of the microbial laminae to form a radial pattern, whereas in Rabigh area, the light-colored gypsum-rich laminae are composed of secondary porphyrotopic, poikilotopic, or granular gypsum crystals. By comparison of the microbial structure in the Miocene gypsum beds with the recent occurrence of the microbial laminites and stromatolites in the solar salt works, it is demonstrated that the organic-rich Miocene gypsum beds were formed in a very shallow salina with slightly fluctuating brine levels.     

Carbonate tidal rhythmites from the Middle Jurassic of Britain

Newly discovered carbonate laminites are described from the Lincolnshire Limestone Formation (Middle Jurassic, Britain). These occur in the upper peloidal unit of fining-upward rhythms which comprise much of the lagoonal lower Lincolnshire Limestone in south Lincolnshire. The flat, millimetre-scale laminations are of three types: (1) alternating peloid-rich, peloid-poor laminae; (2) alternating bioclastic and peloidal laminae; (3) alternating bioclastic and micritic laminae. In all three types, small-scale cross-laminated sets (usually < 40 mm thick) also occur. The laminite horizons are usually < 150 mm thick and have, in some cases, been traced laterally for ～100 m. The close analogy of these carbonate laminites with siliciclastic counterparts favours their interpretation as tidal rhythmites, mechanically deposited in a low intertidal/shallow subtidal setting. The associated sedimentary features and overall stratigraphic-sedimentologic position of the deposits support this conclusion. According to the literature, mechanically deposited as opposed to algally induced carbonate laminites are rare outside the supratidal realm. Possible reasons for the real or imagined scarcity of intertidal/ subtidal carbonate laminites in ancient sedimentary regimes are discussed.     

Reef-capping laminites in the Upper Silurian carbonate- to-evaporite transition, Michigan Basin, south-western Ontario

Silurian pinnacle reefs in the subsurface of the south‐western Ontario portion of the Michigan Basin display a variety of laminated carbonates (laminites) within predominantly muddy reef‐capping facies in the upper part of the Guelph Formation and the overlying A‐1 Carbonate of the Salina Group. Laminites, which are limestone, dolomite or partially dolomitized limestones, have a range of morphologies, from simple planar to a variety of wavy and serrated forms. Individual laminae are composed mainly of micrite, microspar or replacive dolomite, and vary internally from isopachous and continuous over the diameter of the core to non‐isopachous and often discontinuous. Clotted and peloidal micrite, sometimes defining small knobs and chambers, is interpreted as being microbial in origin and occurs within all types of laminites. Fibrous cement locally comprises laminite clasts in breccias or coats clasts in breccias, and also occurs as spherulites in the interparticle spaces in breccias. Although similar laminites have been described from elsewhere in the Michigan Basin and interpreted as caliche, travertine and abiotic subtidal stromatolites, the laminites in south‐western Ontario are most realistically regarded as microbial. The causes for the variations in morphology and characteristics of the constituent laminae are uncertain, although fluctuations in local microenvironmental conditions would have been important, set against a backdrop of an increasingly restricted overall setting. Caliche or travertine origins for these laminites are unlikely in general, except perhaps locally at the subaerial exposure surface at the tops of pinnacle reefs.     

南海北部珠江口盆地西南段断裂特征与成因讨论

珠江口盆地是南海北部陆缘新生代发育的裂陷型盆地,其油气资源丰富,且地处洋陆过渡带,盆地内部断裂特征复杂.在前人研究基础上,利用高分辨率三维地震数据,结合多属性分析技术,完善了区域断裂的精细化解释.将断裂构造类型依据断裂级别与规模划分为控盆一级断裂、控凹二级断裂、控带三级断裂、控圈四级断裂和控层五级小断裂;在盆地西南段发...     

Extension structural records in the Qinshui basin (North China) since the Late Mesozoic

Qinshui basin has abundant coal-bed methane resources and has been undergoing intensive intracontinental rifting and extensional tectonics since the Late Mesozoic. Some fractures, which were previously considered as conjugate shear fractures, are interpreted as joint sets with extension characteristics, for the first time in the Qinshui basin. The widely distributed joint sets with stable attitudes can be divided into four sets. This paper presents updated results of fault-slip datasets collected in different zones of the Qinshui basin and addresses the changes in the direction of extensional stresses since the Late Mesozoic. Based on the analysis results of the slickenline of normal faults, joint sets in the field, and focal mechanism solutions data from the Shanxi Province, we identified four main directions of extension since the Late Mesozoic in the Qinshui basin: (1) Early Cenozoic ENE–WSW (85 ± 15°) extension; (2) Palaeogene NNE–SSW (30 ± 5°) extension; (3) Miocene NW–SE (135 ± 15°) extension; and (4) Late Pliocene–quaternary NNW–SSE (170 ± 5°) extension. The principal extension directions in the Qinshui basin seem to have undergone a counterclockwise rotation from the Early Cenozoic to the Miocene. We prefer that the extension deformation events in the Qinshui basin since the Late Mesozoic were mainly related to the back-arc spreading induced by westward subduction of the paleo-Pacific plate under the Eurasian continent.     

北黄海盆地构造运动学解析

以最新的地质 地球物理资料和北黄海盆地构造几何学特征为基础,采用盆地反演模拟与宏观分析相结合的方法,系统解析了北黄海盆地的构造运动学特征。研究表明,北黄海盆地在中、新生代时期经历了水平伸展、水平挤压、相对平移(走滑)以及垂直差异升降等几种运动型式,其中,水平伸展运动和垂直差异升降运动是北黄海盆地构造运动及形成演化的主体。水平伸展运动可以划分为J3-K1、E2和E3三个主要“伸展事件”,并控制着盆地的成盆演化,其南北向伸展强度均东强西弱,东西向最大伸展强度自中生代到新生代由东向西迁移。水平挤压运动主要有晚白垩世和渐新世末-中新世初期两期。相对平移(走滑)运动伴随水平伸展运动和水平挤压运动发生,使多数NNE向、NW向断裂具有相对压扭或张扭平移(走滑)性质,其中尤以NNE向断裂更为明显。垂直差异升降运动具有“幕式”渐进之特点,晚侏罗世、早白垩世、始新世、渐新世以及中新世中晚期以来为沉降期,其中尤以始新世的沉降速率最大,晚白垩世、古新世、中新世早期为抬升剥蚀期;盆地的中、新生代沉降作用具有明显的自东向西迁移规律:东部坳陷以中生代沉降作用最为显著,中部坳陷主沉降期为始新世,而西部坳陷的快速沉降主要发生在始新世,并一直持续到渐新世。     

泌阳凹陷下第三系核桃园组湖相隐藻层纹石岩的发现及其环境意义

泌阳凹陷下第三系核桃园组,在沉积上表现为一个大的湖退层序。在深盆浅水和干化深盆时期,陆源碎屑周期性地输入与泥坪上生长的造碳酸盐岩非骨骼藻群落结合,形成了不同频率的隐藻层纹石岩旋回。由于隐藻层纹石岩的特殊组构、沉积层序和对沉积环境的较大依存性,使之成为古环境分析的良好指标,也为油气勘探提供有价值的依据。     

西秦岭北缘构造带新生代盆地南部边界断层带结构与构造变形演化

西秦岭北缘构造带是青藏高原东北缘的主要构造边界之一,北缘断层及其所控制的新生代沉积盆地是青藏高原东北缘新生代盆—山格局演化、高原扩展隆升与变形的地质记录。因此,西秦岭北缘构造带的断裂构造和断裂控制的沉积盆地研究对于理解青藏高原构造系统形成和高原隆升过程都具有重要的科学意义。本文通过对西秦岭北缘新生代盆地的南部边界断层F1断层结构分带、断层岩类型、几何学—运动学特征分析,获得如下认识：1）F1断层总体走向为290°～300°,倾向北北东,倾角60°～80°,发育近百米宽的由韧性、韧脆性和脆性断层岩等组成的结构复杂的断层带;2）构造分析揭示了F1断层至少经历了 3期构造变形事件,第一期为韧性—韧脆性伸展正断层作用,第二期为脆性高角度挤压逆冲断层作用,第三期为近直立的脆性斜向左旋走滑作用;3）该断层近百米宽的断层带内形成于不同构造层次的韧性、韧脆性、脆性等变形现象叠加交织出现在现今地壳浅表层次,说明该断层带经历了从早期较深层次韧性变形域逐渐抬升而进入晚期较浅层次的脆韧性变形域到现今的脆性变形域的韧—脆性变形机制转换;4）根据F1断层对西秦岭北缘渐新统—中新统漳县含盐红层盆地的空间构造配置、控制和改造以及新生代区域构造变形演化历史分析,认为第一期韧性—韧脆性伸展正断层作用与渐新世—中新世断陷盆地形成相匹配,活动时代为晚渐新世—晚中新世;第二期脆性高角度挤压逆冲作用与渐新世—中新世地层翘起、褶皱和底部抬升剥蚀及上新世磨拉石盆地充填相对应,活动时代应该始于中新世末期或上新世早期,持续至第四纪早期;第三期斜向左旋走滑则与西秦岭北缘断层带第四纪以来广泛发育的左旋走滑作用相对应。综上所述,西秦岭北缘新生代漳县盆地南部边界断层F1,虽然仅是北缘构造带中一条断层,但作为构造敏感带,其多期变形历史应该代表了青藏高原东北缘新生代以来的构造变形演化及构造体制转换过程。如果这一新生代沉积盆地边界断层F1在渐新世—中新世一直处于伸展正断作用,那么西秦岭北缘在这个阶段应该处于地壳伸展拉张状态,渐新世—中新世漳县盆地只能是伸展断陷盆地而不可能是挤压挠曲前陆盆地或压陷盆地。因此,我们认为印度—欧亚板块碰撞汇聚产生的构造挤压缩短和地壳隆升效应在中新世尚未波及到西秦岭北缘区域。F1断层在中新世末—上新世初的构造反转挤压冲断和上新世具有再生前陆磨拉石堆积出现才标志着西秦岭北缘卷入青藏高原挤压构造动力学系统。     

银根-额济纳旗盆地西缘的中-新生代伸展构造

银根-额济纳旗盆地简称银额盆地,是中亚造山带南缘的一个中-新生代沉积盆地。最近的野外地质调查,在其西缘发现早侏罗世和第四纪晚期的伸展构造。早侏罗世的伸展构造为一系列走向NNW-SSE 的正断层,是下侏罗统的同沉积断层。这组正断层与银额盆地内NNE-SSW 走向的正断层组合成共轭断裂系统,指示古构造应力场的最大主拉张应力方向为近E-W。它们是中亚造山带（南缘）造山后应力伸展阶段的构造变形。第四纪晚期的伸展构造是由两条倾向相向的正断层组合成的地堑构造,走向进E-W,可能代表了喜马拉雅碰撞造山远程效应脉动式演化过程的一个构造间歇期。     

Neotectonic evolution of the northwestward arched segment of the Central Anatolian Fault Zone,Central Anatolia,Turkey

Central Anatolia has undergone complex Neotectonic deformation since Late Miocene–Pliocene times. Many faults and intracontinental basins in this region were either formed, or have been reactivated, during this period. The eastern part of central Anatolia is dominated by a NE–SW-trending, left lateral transcurrent structure named the Central Anatolian fault zone located between Sivas in the northeast and west of Mersin in the southwest. Around the central part, it is characterized by transtensional depressions formed by left stepping and southward bending of the fault zone.Pre-Upper Miocene basement rocks of the region consist of the central Anatolian crystalline complex and a sedimentary cover of Tertiary age. These rock units were strongly deformed by N–S convergence. The entire area emerged to become the site of erosion and formed a vast plateau before the Late Miocene. A NE–SW-trending extensional basin developed on this plateau in Late Miocene–Early Pliocene times. Rock units of this basin are characterized by a thick succession of pyroclastic rocks intercalated with calcalkaline–alkaline volcanics. The volcanic sequence is unconformably overlain by Pliocene lacustrine–fluviatile deposits intercalated with ignimbrites and tuffs. Thick, coarse grained alluvial/colluvial fan deposits of marginal facies and fine grained clastics and carbonates of central facies display characteristic synsedimentary structures with volcanic intercalations. These are the main lines of evidence for development of a new transtensional Hırka–Kızılırmak basin in Pliocene times. Reactivation of the main segment of the Central Anatolian fault zone has triggered development of depressions around the left stepping and southward bending of the central part of this sinistral fault zone in the ignimbritic plateau during Late Pliocene–Quaternary time. These transtensional basins are named the Tuzla Gölü and Sultansazlığı pull-apart basins. The Sultansazlığı basin has a lazy S to rhomboidal shape and displays characteristic morphologic features including a steep and stepped western margin, large alluvial and colluvial fans, and a huge composite volcano (the Erciyes Dağı).The geometry of faulting and formation of pull-apart basins can be explained within the framework of tectonic escape of the wedge-like Anatolian block, bounded by sinistral East Anatolian fault zone and dextral North Anatolian transform fault zone. This escape may have been accomplished as lateral continental extrusion of the Anatolian Plate caused by final collision of the Arabian Plate with the Eurasian Plate.     

Neotectonics of East Anatolian Plateau (Turkey) and Lesser Caucasus: implication for transition from thrusting to strike-slip faulting

The east Anatolian plateau and the Lesser Caucasus are characterised and shaped by three major structures: (1) NW- and NE-trending dextral to sinistral active strike-slip faults, (2) N-S to NNW-trending fissures and /or Plio-Quaternary volcanoes, and (3) a 5-km thick, undeformed Plio-Quaternary continental volcano-sedimentary sequence accumulated in various strike-slip basins. In contrast to the situation in the east Anatolian plateau and the Lesser Caucasus, the Transcaucasus and the Great Caucasus are characterised by WNW-trending active thrust to reverse faults, folds, and 6-km thick, undeformed (except for the fault-bounded basin margins) continuous Oligocene-Quaternary molassic sequence accumulated in actively developing ramp basins. Hence, the neotectonic regime in the Great Caucasus and the Transcaucasus is compressional–contractional, and Oligocene-Quaternary in age; whereas it is compressional–extensional, and Plio-Quaternary in age in the east Anatolian plateau and the Lesser Caucasus.Middle and Upper Miocene volcano-sedimentary sequences are folded and thrust-to-reverse-faulted as a result of compressional–contractional tectonic regime accompanied by mostly calc-alkaline volcanic activity, whereas Middle Pliocene-Quaternary sequences, which rest with angular unconformity on the pre-Middle Pliocene rocks, are nearly flat-lying and dominated by strike-slip faulting accompanied by mostly alkali volcanic activity implying an inversion in tectonic regime. The strike-slip faults cut and displace dykes, reverse to thrust faults and fold axes of Late Miocene age up to maximum 7 km: hence these faults are younger than Late Miocene, i.e., these formed after Late Miocene. Therefore, the time period between late Serravalian (∼ 12 Ma) continent–continent collision of Arabian and Eurasian plates and the late Early Pliocene inversion in both the tectonic regime, basin type and deformation pattern (from folding and thrusting to strike-slip faulting) is here termed as the Transitional period.Orientation patterns of various neotectonic structures and focal mechanism solutions of recent earthquakes that occurred in the east Anatolian plateau and the Caucasus fit well with the N–S directed intracontinental convergence between the Arabian plate in the south and the Eurasian plate in the north lasting since Late Miocene or Early Pliocene in places.     

Complex basin evolution in the Gökova Gulf region: implications on the Late Cenozoic tectonics of southwest Turkey

Southwestern Turkey experienced a transition from crustal shortening to extension during Late Cenozoic, and evidence of this was recorded in four distinct basin types in the Mu?la–Gökova Gulf region. During the Oligocene–Early Miocene, the upper slices of the southerly moving Lycian Nappes turned into north-dipping normal faults due to the acceleration of gravity. The Kale–Tavas Basin developed as a piggyback basin along the fault plane on hanging wall blocks of these normal faults. During Middle Miocene, a shift had occurred from local extension to N–S compression/transpression, during which sediments in the Eskihisar–T?naz Basins were deposited in pull-apart regions of the Menderes Massif cover units, where nappe slices were already eroded. During the Late Miocene–Pliocene, a hiatus occurred from previous compressional/transpressional tectonism along intermountain basins and Yata?an Basin fills were deposited on Menderes Massif, Lycian Nappes, and on top of Oligo–Miocene sediments. Plio-Quaternary marked the activation of N–S extension and the development of the E–W-trending Mu?la–Gökova Grabens, co-genetic equivalents of which are common throughout western Anatolia. Thus, the tectonic evolution of the western Anotolia during late Cenozoic was shifting from compressional to extensional with a relaxation period, suggesting a non-uniform evolution.     

西藏安多-错那湖地堑的第四纪地质、断裂活动及其运动学特征分析

地表调查和初步的沉积物年代测试结果表明,晚第四纪期间,在安多-错那地堑中主要发育了分别形成于44.2kaB.P.和9～7kaB.P.左右的两套湖泊沉积物和约42kaB.P.以来的5套冲、洪积物。在安多-错那地堑的边界主要发育了包括安多南缘断裂、北缘断裂、错那湖东缘断裂和西缘断裂共4条第四纪正断层。其中活动强度最大的为安多北缘断裂,其第四纪最小垂直活动速率为0.24±0.02mm/a;其次为安多南缘断裂和错那湖东、西两侧边界断裂,它们的最小垂直速率分别为0.19mm/a,0.12～0.16mm/a和0.10～0.12mm/a。晚第四纪以来的断裂活动主要集中在平均垂直活动速率为0.41±0.22mm/a的安多北缘断裂带的西段。安多及邻区现今的地表构造格局及断裂带的几何学和运动学特征符合近南北向地壳缩短背景下由于近东西向伸展变形而引发的菱形断块发育模式。根据断层的活动速率估算结果,晚第四纪期间安多-错那地堑的平均伸展速率为0.25±0.15mm/a,而整个羌塘块体总的东西向伸展变形速率可能达到11±8mm/a。     

银额盆地及周缘的两期晚新生代伸展构造:喜马拉雅碰撞造山远程效应的两个构造间歇期

银额盆地是中亚造山带南缘的一个中-新生代沉积盆地。在2017～2018年的野外地质调查期间,我们在银额盆地及周缘发现了多处晚新生代的伸展构造。这些伸展构造主要是一系列的正断层,还有同期的“X”共轭节理。相邻的两条倾向相对的正断层形成地堑。杭乌拉南正断层和鼎新镇北地堑形成于第四纪晚期,北山煤矿的正断层活动时间可能也是第四纪晚期。第四纪晚期正断层走向近E-W;伴生的鼎新镇北“X”共轭节理由走向NE-SW和NW-SE两组近直立的节理组成。苏宏图背斜上发育的正断层形成于新近纪晚期—第四纪早期,走向近E-W。古应力场分析,两期伸展构造的最大主拉张应力方向都是近N-S。这两期晚新生代伸展构造属于喜马拉雅碰撞造山的远程效应的组成部分,代表了远程效应脉动式演化过程的两个构造间歇期。     

西藏门巴地区嘉黎断裂带变形特征及演化

地质剖面测量和区域构造解析方法研究表明,嘉黎断裂是一条多期活动并在不同时期显示不同性质的、有着长期发展历史的深大断裂。在晚三叠世-侏罗纪时期,班公湖-怒江洋盆南侧比如弧后盆地发生裂解,此时的嘉黎断裂应是北倾的正断层,控制着弧后盆地的沉积。晚侏罗世-早白垩世时期,伴随着盆地的消亡,出现一系列由南向北的逆冲断裂和蛇绿岩的就位。中新世至第四纪,嘉黎断裂带表现为伸展构造体系,局部出现右旋走滑,形成机理是青藏高原隆升导致构造块体不均匀运动和塌陷所致。     

北部湾盆地乌石凹陷东洼伸展滑脱构造发育演化模式及其油气地质意义

北部湾盆地乌石凹陷从古新世早期到渐新世末期经历了多幕次的伸展,在裂陷Ⅱ幕时期形成了一组近E-W向的伸展滑脱断裂系,但其形成机制及演化过程尚未明确. 基于油气勘探过程中获取的全新高精度三维地震资料,应用构造?地层综合解释以及定量分析的技术方法,对乌石凹陷东洼伸展滑脱构造进行了深入的解析. 结果表明,乌石东洼新生代地层共发育7条近E-W或NE-SW向展布的伸展滑脱断层（Fa?Fg）,这些伸展滑脱断层与北倾的7号断层相向倾斜发育,共同控制了流沙港组一段到涠洲组一段的跷跷板式地层沉积和大型滚动背斜的形成. 从演化上来讲,在始新世早中期（T100-T83）盆地为由NE-SW向展布的7号断层和局部基底小规模正断层控制的地堑或半地堑盆地,早期局部沉积的流沙港组三段被晚期连续沉积的厚层流沙港组二段油页岩覆盖. 始新世晚期?渐新世晚期（T83-T60）,盆地沉积了由对倾发育的伸展滑脱断层和7号断层共同控制的流沙港组一段?涠洲组一段,对倾断层的先后活动导致了沉降沉积中心的迁移,控制了复杂的“跷跷板式”滚动背斜及“包心菜”构造的发育. 新近纪以来（T60-海底）,盆地的构造活动性减弱,转变为坳陷型盆地. 描述了乌石凹陷东洼裂陷Ⅱ幕时期形成的伸展滑脱构造的几何学特征,并解析了伸展滑脱构造的形成模式,提出了滑脱断裂发育有自下坡断层组向上坡断层组迁移的规律,对解决油气的运移、储存、保存等问题有重要的意义.      

The Çubukludağ graben,south of İzmir: its tectonic significance in the Neogene geological evolution of the western Anatolia

Field studies on the Neogene successions in south of İzmir reveal that subsequent Neogene continental basins were developed in the region. Initially a vast lake basin was formed during the Early–Middle Miocene period. The lacustrine sediments underwent an approximately N–S shortening deformation to the end of Middle Miocene. A small portion of the basin fill was later trapped within the N–S-trending, fault-bounded graben basin, the Çubukludağ graben, opened during the Late Miocene. Oblique-slip normal faults with minor sinistral displacement are formed possibly under N–S extensional regime, and controlled the sediment deposition. Following this the region suffered a phase of denudation which produced a regionwide erosional surface suggesting that the extension interrupted to the end of Late Miocene–Early Pliocene period. After this event the E–W-trending major grabens and horsts of western Anatolia began to form. The graben bounding faults cut across the Upper Miocene–Pliocene lacustrine sediments and fragmented the erosional surface. The Çubukludağ graben began to work as a cross graben between the E–W grabens, since that period.     

吐哈盆地中央构造带正反转演化特征

吐哈盆地中央构造带由火焰山构造和七克台构造组成。中央构造带形成于三叠纪晚期至侏罗纪早期,表现为伸展构造特征,生长断层上盘地层厚度明显大于下盘,并于断层上盘所在的台北凹陷形成沉降中心。晚侏罗世,由于拉萨陆块与欧亚大陆的碰撞作用导致吐哈盆地由伸展盆地转变为挤压盆地,中央构造带也于此时发生构造反转,由早期的伸展正断层转变为挤压逆断层。发生于55Ma的喜山构造事件对天山地区产生了深刻的影响,但影响时间略有滞后,大致发生在晚渐新世至早中新世,中央构造带即在此次构造事件中强烈变形,逆冲出露于地表。     

The composition and age of the Argillite Sequence (sedimentary cover of the continental slope, Sea of Japan)

The Argillite Sequence located at the base of the sedimentary cover on the continental slope of the Sea of Japan was studied by petrographic, palynological, and X-ray diffraction methods. Two spores-pollen complexes were distinguished in it: the Late Oligocene reflecting cooling and the Early Miocene corresponding to initiated warming. The data obtained indicate that the sequence is composed of terrigenous silty-clayey sediments that accumulated in shallow coastal-marine settings. The global sea-level rise at the Early-Middle Miocene transition, combined with the regional tectonic processes, determined the basin deepening, owing to which the argillite sequence was overlain by thick Middle Miocene diatomaceous-clayey sediments. Due to tectonic movement along existing faults in the terminal Late Miocene, the argillite sequence occurring initially at depths of at least 400–500 m was locally exhumed to the basin bottom.     

Precession-punctuated growth of a late Miocene submarine-fan lobe on Gavdos (Greece)

Sedimentary cycles in an upper Miocene succession of hemipelagic sediments (marls) and laminites (sapropels) were deposited in an outerarc basin and are related to the astronomical cycles of precession and eccentricity. Individual marl-laminite couplets correspond with the cycle of precession which has a periodicity of about 22 kyr. The lower part of the succession contains a turbidite interval comprising a number of distinct turbidite sequences. The turbidite sequences occur within or substitute entirely the laminite beds, so that turbidite deposition is similarly precession punctuated. The turbidite facies is characteristic for small, prograding fan lobes fed by small-volume turbidites. The abundant plant remains, the local palaeogeographic setting and the association with laminites (related to wet climate) suggest a river-fed submarine fan-lobe, where the timing of sediment transport is largely controlled by river floods during periods of high precipitation and continental run-off. The onset and ending of the turbidite interval is most likely linked with either autocyclic processes or by tectonic steepening of the hinterland relief. Sea-level changes seem least important for the triggering of turbidites, which is in contrast with current beliefs.