Stages of development in the Polish Carpathian Foredeep basin

In southern Poland, Miocene deposits have been recognised both in the Outer Carpathians and the Carpathian Foredeep (PCF). In the Outer Carpathians, the Early Miocene deposits represent the youngest part of the flysch sequence, while in the Polish Carpathian Foredeep they are developed on the basement platform. The inner foredeep (beneath the Carpathians) is composed of Early to Middle Miocene deposits, while the outer foredeep is filled up with the Middle Miocene (Badenian and Sarmatian) strata, up to 3,000mthick. The Early Miocene strata are mainly terrestrial in origin, whereas the Badenian and Sarmatian strata are marine. The Carpathian Foredeep developed as a peripheral foreland basin related to the moving Carpathian front. The main episodes of intensive subsidence in the PCF correspond to the period of progressive emplacement of the Western Carpathians onto the foreland plate. The important driving force of tectonic subsidence was the emplacement of the nappe load related to subduction roll-back. During that time the loading effect of the thickening of the Carpathian accretionary wedge on the foreland plate increased and was followed by progressive acceleration of total subsidence. The mean rate of the Carpathian overthrusting, and north to north-east migration of the axes of depocentres reached 12 mm/yr at that time. During the Late Badenian-Sarmatian, the rate of advance of the Carpathian accretionary wedge was lower than that of pinch-out migration and, as a result, the basin widened. The Miocene convergence of the Carpathian wedge resulted in the migration of depocentres and onlap of successively younger deposits onto the foreland plate.     

中昆仑北部地区构造地层学初步研究

中昆仑北部造山带可分为 5个构造地层区 :白干湖、求勉雷克、大九坝、祁漫塔格南缘和祁漫塔格北缘。白干湖和求勉雷克构造地层区出露前寒武纪变质结晶基底 ;早古生代期间 ,祁漫塔格洋沿鸭子泉—阿特阿特坎河断裂向北西俯冲碰撞 ,在祁漫塔格北缘沉积了古海沟岛弧浊积岩、晚泥盆世蛇绿混杂岩 ,在祁漫塔格南缘被动大陆边缘上发育晚泥盆世前陆磨拉石沉积 ;晚古生代早期 ,昆中求勉雷克地区简单剪切滑覆 ,在祁漫塔格南、北缘形成浅海相沉积 ,而大九坝地区由于断层高角度伸展 ,沉积了一套海相碳酸盐岩建造 ;晚古生代晚期 ,特提斯洋沿昆中断裂斜向俯冲 ,在大九坝出露了托库孜达坂蛇绿混杂岩和早二叠世前陆盆地堆积 ;晚三叠世陆相火山岩出露于祁漫塔格山南缘。     

Late Cretaceous to early Miocene deposits of the Carpathian foreland basin in southern Moravia

 The Late Cretaceous to Early Miocene strata of the Carpathian foreland basin in southern Moravia (Czech Republic) are represented by a variety of facies which reflects the evolution of the foreland depositional system. However, because of the intensive deformation and tectonic displacement and the lack of diagnostic fossils the stratigraphic correlation and paleogeographic interpretation of these strata are difficult and often controversial. In order to better correlate and to integrate them into a broader Alpine–Carpathian foreland depositional system, these discontinuous and fragmentary strata have been related to four major tectonic and depositional events: (a) formation of the Carpathian foreland basin in Late Cretaceous which followed the subduction of Tethys and subsequent deformation of the Inner Alps-Carpathians; (b) Middle to Late Eocene transgression over the European foreland and the Carpathian fold belt accompanied by deepening of the foreland basin and deposition of organic-rich Menilitic Formation; (c) Late Oligocene to Early Miocene (Egerian) uplifting and deformation of inner zones of the Carpathian flysch belt and deposition of Krosno-type flysch in the foreland basin; and (d) Early Miocene (Eggenburgian) marine transgression and formation of late orogenic and postorogenic molasse-type foreland basin in the foreland. These four principal events and corresponding depositional sequences are recognized throughout the region and can be used as a framework for regional correlation within the Alpine–Carpathian foreland basin. Received: 18 August 1998 / Accepted: 9 June 1999     

前陆盆地沉降机理和地层模型

前陆盆地形成的主要原因是造山带负载导致的岩石圈挠曲。逆冲作用造成地壳增厚,造山带的巨大质量又导致下部岩石圈的区域均衡沉降,从而临近和平行于造山带发育了凹陷。另外,前陆盆地的演化也受到沉积物供应、盆地内沉积物扩散能力、岩石圈强度、造山带逆冲速率、全球海平面变化、和俯冲有关的动力沉降及俯冲负载等众多其它因素的影响。本文阐述了这些因素与前陆盆地沉降的关系,介绍了与幕式逆冲有关的地层模型和欠补偿-过补偿地层模型。希望本文能够对中国西北地区前陆盆地的研究起到一定的借鉴意义。     

The structure and stratigraphy of deepwater Sarawak,Malaysia: Implications for tectonic evolution

The structural-stratigraphic history of the North Luconia Province, Sarawak deepwater area, is related to the tectonic history of the South China Sea. The Sarawak Basin initiated as a foreland basin as a result of the collision of the Luconia continental block with Sarawak (Sarawak Orogeny). The foreland basin was later overridden by and buried under the prograding Oligocene-Recent shelf-slope system. The basin had evolved through a deep foreland basin (‘flysch’) phase during late Eocene–Oligocene times, followed by post-Oligocene (‘molasse’) phase of shallow marine shelf progradation to present day.Seismic interpretation reveals a regional Early Miocene Unconformity (EMU) separating pre-Oligocene to Miocene rifted basement from overlying undeformed Upper Miocene–Pliocene bathyal sediments. Seismic, well data and subsidence analysis indicate that the EMU was caused by relative uplift and predominantly submarine erosion between ∼19 and 17 Ma ago. The subsidence history suggests a rift-like subsidence pattern, probably with a foreland basin overprint during the last 10 Ma. Modelling results indicate that the EMU represents a major hiatus in the sedimentation history, with an estimated 500–2600 m of missing section, equivalent to a time gap of 8–10 Ma. The EMU is known to extend over the entire NW Borneo margin and is probably related to the Sabah Orogeny which marks the cessation of sea-floor spreading in the South China Sea and collision of Dangerous Grounds block with Sabah.Gravity modelling indicates a thinned continental crust underneath the Sarawak shelf and slope and supports the seismic and well data interpretation. There is a probable presence of an overthrust wedge beneath the Sarawak shelf, which could be interpreted as a sliver of the Rajang Group accretionary prism. Alternatively, magmatic underplating beneath the Sarawak shelf could equally explain the free-air gravity anomaly. The Sarawak basin was part of a remnant ocean basin that was closed by oblique collision along the NW Borneo margin. The closure started in the Late Eocene in Sarawak and moved progressively northeastwards into Sabah until the Middle Miocene. The present-day NW Sabah margin may be a useful analogue for the Oligocene–Miocene Sarawak foreland basin.     

Tectonically-driven underfilled–overfilled cycles,the middle Cretaceous in the northern Cordilleran foreland basin

It is shown that the middle Cretaceous succession in the northern Cordilleran foreland basin consists of several-million-year tectonically-driven cycles comprising two components: strata deposited in an underfilled basin with a prominent forebulge zone and strata deposited in an overfilled basin lacking evidence of a forebulge. The episodic thrusting of the Cordilleran orogenic wedge and its rich sediment supply to the basin are two main controlling factors for the formation of these cycles. A qualitative model of several-million-year tectonically-driven underfilled–overfilled cycle for migration and stratigraphic fill in this basin is proposed. During the early underfilled period (orogenic loading period), due to orogenic loading of emplaced thrust sheets, flexural subsidence is created in the region proximal to the mountain belt and a prominent forebulge is developed. During the late underfilled period (early orogenic unloading period), as the cratonward migration of the subsidence center of sediment loading in the foredeep zone, forebulge zones and backbulge zones migrate cratonwards, forming a diachronic erosion surface in the central basin. During the overfilled period (late orogenic unloading period), a prominent erosion forms in the proximal basin and a peripheral sag develops above the forebulge area of the previous underfilled period. This model may provide a pattern to subdivide sedimentary successions in the Cordilleran foreland basin. Using this model, alternative interpretations are suggested for some important, but controversial stratigraphic phenomena in the Cretaceous Cordilleran foreland basin: traditionally defined eustatic highstands, wide sedimentation area of the basin, erosion surfaces and widespread subtle topographic uplifts in the central basin, high-frequency coarsening-up cycles, extensively distributed erosive-based sandstones and conglomerates enclosed in marine mudstones.     

川西前陆盆地中—新生代沉积迁移与构造转换

川西前陆盆地中—新生代各构造层的残余厚度展布和沉积特征分析发现,四川克拉通周缘的前陆盆地在晚三叠世时期发育于龙门山山前,明显属于龙门山褶皱逆冲构造载荷所形成的前渊凹陷;侏罗纪早期的沉积地层呈面状分布,没有表现出显著的挠曲沉降,指示了一个构造相对平静的阶段;中侏罗世早期前渊凹陷迁移至龙门山北段和米仓山山前,前渊沉积从晚三叠世的北东向转换为近东西向,广泛的湖泊相沉积预示了前陆盆地的欠充填状态;中侏罗世中晚期,川西盆地沉降中心又迁移到大巴山山前,相应的挠曲变形又从近东西向转化为北西向,构成了大巴山的前渊凹陷;晚侏罗世—早白垩世时期,沉降中心再次回到米仓山山前,巨厚的前渊凹陷沉积指示了米仓山冲断带的主要活动时期;白垩纪末—古近纪的前渊凹陷则跃迁至雅安—名山地区。川西前陆盆地的同造山沉降中心以四川盆地中心为核心在西部和北部呈弧形迁移,沉积序列不断更替和叠加。中生界各构造层底界构造图显示现今的构造低部位位于川西北地区和川西南地区,在川西北地区均有东西走向的等值线分布,而川西南地区等值线走向则为北东-南西向。因此分析认为,晚侏罗世至早白垩世的构造变形可能控制了川西盆地现今的地层变形,形成了川西北地区的南北向构造挤压结构,而晚期的新生代构造变形则主要体现在川西盆地的西南部,形成北东-南西向的地层展布特征。     

The Cimmerian Orogeny in northern Iran: tectono-stratigraphic evidence from the foreland

From the Permian onwards, the Gondwana-derived Iran Plate drifted northward to collide with Eurasia in the Late Triassic, thereby closing the Palaeotethys. This Eo-Cimmerian Orogeny formed the Cimmeride fold-and-thrust belt. The Upper Triassic–Middle Jurassic Shemshak Group of northern Iran is commonly regarded as the Cimmerian foreland molasse. However, our tectono-stratigraphic analysis of the Shemshak Group resulted in a revised and precisely dated model for the Triassic–Jurassic geodynamic evolution of the Iran Plate: initial Cimmerian collision started in the Carnian with subsequent Late Triassic synorogenic peripheral foreland deposition (flysch, lower Shemshak Group). Subduction shifted south in the Norian (onset of Neotethys subduction below Iran) and slab break-off around the Triassic–Jurassic boundary caused rapid uplift of the Cimmerides followed by Liassic post-orogenic molasse (middle Shemshak Group). During the Toarcian–Aalenian (upper Shemshak Group), Neotethys back-arc rifting formed a deep-marine basin, which developed into the oceanic South Caspian Basin during the Late Bajocian–Late Jurassic.     

中生代羌塘前陆盆地充填序列及演化过程

中生代羌塘前陆盆地位于青藏高原巨型造山带内 ,夹于金沙江缝合带与班公湖—怒江缝合带之间 ,是一个与两侧缝合带逆冲作用相关的沉积盆地 ,由羌北盆地 (对应于金沙江缝合带 )、羌南盆地 (对应于班公湖—怒江缝合带 )和中央隆起带构成 ,其中中央隆起是北部前陆盆地和南部前陆盆地共有的前陆隆起 ,显示为对称型复合前陆盆地 ;该盆地形成于晚三叠世 ,并持续发育至早白垩世 ,盆地中充填了巨厚的同构造期的复理石和磨拉石 ,具有总体向上变粗变浅的充填序列 ,以不整合面可将其划分为 5个由顶底不整合面限制的构造层序 ,其中晚三叠世诺利期构造层序对应于金沙江缝合带主碰撞期 ,晚三叠世瑞替期构造层序对应于金沙江缝合带碰撞闭合后冲断抬升 ,早侏罗世构造层序对应于班公湖—怒江缝合带初始逆冲推覆 ,中侏罗世—早白垩世构造层序对应于班公湖—怒江缝合带主碰撞期 ,中白垩世构造层序为班公湖—怒江缝合带碰撞闭合后冲断抬升与金沙江缝合带冲断抬升的产物 ,为中生代羌塘盆地关闭后的磨拉石建造     

再论台湾造山带构造格架与演化过程SCIEI北大核心CSCD

台湾造山带是中新世晚期以来相邻菲律宾海板块往北西方向移动,导致北吕宋岛弧系统及弧前增生楔与欧亚大陆边缘斜碰撞形成的。目前该造山带仍在活动,虽然规模很小,但形成了多数大型碰撞造山带中的所有构造单元,是研究年轻造山系统的理想野外实验室,为理解西太平洋弧-陆碰撞过程和边缘海演化提供了一个独特的窗口。本文总结了二十一世纪以来对台湾造山带的诸多研究进展,讨论了其构造单元划分及演化过程。我们将台湾造山带重新划分为6个构造单元,由西至东分依次为:(1)西部前陆盆地;(2)中央山脉褶皱逆冲带;(3)太鲁阁带;(4)玉里-利吉蛇绿混杂岩带;(5)纵谷磨拉石盆地;(6)海岸山脉岛弧系统。其中,西部前陆盆地为6.5Ma以来伴随台湾造山带的隆升剥蚀形成沉积盆地。中央山脉褶皱逆冲带为新生代(57~5.3Ma)欧亚大陆东缘伸展盆地沉积物由于弧-陆碰撞受褶皱、逆冲及变质作用改造形成的。太鲁阁带是造山带中的古老陆块,主要记录中生代古太平洋俯冲在欧亚大陆活动边缘形成的岩浆、沉积和变质岩作用。玉里-利吉蛇绿混杂岩带和海岸山脉岛弧系统分别为中新世中期(~18Ma)以来南中国海板块向菲律宾海板块之下俯冲形成的岛弧和弧前增生楔,其中玉里混杂岩中有典型低温高压变质作用记录,变质年龄为11~9Ma;岛弧火山作用的主要时限为9.2~4.2Ma。纵谷磨拉石盆地记录1.1Ma以来的山间盆地沉积。台湾造山带的构造演化可划分为4个阶段:(a)古太平洋板块俯冲与欧亚大陆边缘增生阶段(200~60Ma);(b)欧亚大陆东缘伸展和南中国海扩张阶段(60~18Ma);(c)南中国海俯冲阶段(18~4Ma);(d)弧-陆碰撞阶段(<6Ma)。台湾弧-陆碰撞造山带是一个特殊案例,其弧-陆碰撞并不伴随着弧-陆之间的洋盆消亡,而是由于北吕宋岛弧及弧前增生楔伴随菲律宾海板块运动向西北方走滑,仰冲到欧亚大陆边缘,形成现今的台湾造山带。     

楚雄中生代前陆盆地的构造沉降史研究

云南楚雄盆地位于场子陆块的西南边缘,为一典型的中生代周缘前陆盆地,盆地演化阶段明显,晚三叠世为前陆早期复理石沉积,侏罗纪则为前陆晚期磨拉石沉积。对盆地构造沉降史研究后笔者认为：①晚三叠世复理石沉积盆地构造沉降幅度巨大,沉降与沉积中心位于盆地最西部,紧邻古哀牢山造山带,沉积体呈形楔形展布;③侏罗纪磨拉石沉积盆地构造沉降和沉积中心以及前缘隆起向内陆方向迁移明显;③中生代构造快速沉降的沉积体的楔形展布表     

Late Miocene–Quaternary volcanism, tectonics and drainage system evolution in the East Carpathians, Romania

Middle Miocene (Sarmatian) convergence created the fold and thrust belt of the Eastern Carpathians of Romania, which subsequently experienced post-collisional crustal deformation combined with calc-alkaline and alkalic-basaltic volcanism in late Miocene–Quaternary time. This deformation led to the rise of the Cǎlimani–Gurghiu–Harghita volcanic mountains and to the subsidence of the N–S-oriented intramontane Borsec/Bilbor–Gheorgheni–Ciuc and Braşov pull-apart basins, and the E-oriented monocline-related Fǎgǎraş basin. The regional drainage network is the composite of:

(1) Older E-, SE- and S-flowing rivers, which cross the Carpathians, radiate towards the foreland and were probably established during the Middle Miocene (Sarmatian) collision event.

(2) A more recent drainage system related to the contemporaneous development of the volcanoes and intramontaneous basins, which generally drains westward into the Transylvanian Basin since late Miocene time and has been capturing the older river system.

The older river drainage system has also been modified by Late Pliocene–Quaternary folding, thrusting and monoclinal tilting along the Pericarpathian orogenic front and by reactivated transverse high angle basement faults, which cross the Eastern Carpathian foreland.     

Development of tectonostratigraphy in distal part of foreland basin in southwestern Taiwan

In the young and active tectonic belt of southwestern Taiwan, reconstructed stratigraphy in the distal part of the foreland basin reveals at least two regional unconformities with the younger ones covering the areas farther from the mountain belt. In contrast with the previously proposed monotonous basin development, the temporal–spatial distribution of the unconformities indicates the back-and-forth migration of the foreland basin margin. Three distinct episodes of rapid subsidence during the foreland basin development have also been identified. The onset of the basin development can be well constrained by the initial rapid subsidence at 4.4–4.2 Ma, which happened only in the proximal part of the basin. This was followed by two younger episodes of rapid subsidence events at 2–1.8 Ma and 0.45 Ma, which were encountered initially in the areas progressively farther from the orogenic belt.We propose a model of episodic tectonic evolution in the distal part of the foreland basin in southwestern Taiwan. During each episode of rapid subsidence, uplifting that corresponds to the forebulge began with a concurrent rapid subsidence in the areas closer to the basin center and was followed by rapid subsidence and deposition of widespread strata onlapping toward the basin margin. Part of the widespread strata and its overlying deposits would be eroded in the beginning of the next episode when the forebulge shifted toward the orogenic belt. In general, rate of forebulge migrating away from the orogenic belt during the early stage was slower than that derived from a previously proposed kinematic model of a steady migration of the orogenic belt. This might be due to a rifted and weaker lithosphere beneath the foreland basin. Once the foreland basin migrated onto the less stretched lithosphere, the basin would expand rapidly into the craton.     

青藏高原中侏罗世-早白垩世羌塘复合型前陆盆地充填模式

根据沉积物碎屑组分、粗碎屑楔状体、边缘相、古流向和沉积、沉降中心等重建了盆地结构、古地理和古地貌,认为该盆地是在中侏罗世-早白垩世多岛洋体制下形成的一种复杂的、特殊类型的复合前陆盆地,它的形成和发展同金沙江缝合带与班公湖-怒江缝合带的碰撞和对冲有关,是盆地两侧板块边缘的大型逆冲作用的产物。在此基础上,根据中央隆起地貌景观交替性变化和盆地中“三砂二灰”的幕式沉积特点,将中侏罗世-早白垩世羌塘前陆盆地演化过程分为 5个阶段,其中巴通期和牛津-提唐期是羌塘盆地南北两侧构造活动相对平静期,而巴柔期、卡洛期、提唐-贝里阿斯期是羌塘盆地南北两侧构造活动强烈时期,强烈的逆冲推覆作用产生大量的构造负载,导致中央隆起强烈地挠曲隆升,造成了盆地中的幕式沉积,产生构造层序和层序,恢复了羌塘前陆盆地沉积记录与两侧缝合带的逆冲作用的相互关系.     

中国前陆盆地构造地质特征综述与油气勘探

中国特定环境下发育的前陆盆地和冲断带在地质构造上具有许多的特殊性。在综述前人认识的基础上,笔者通过对中国前陆盆地的构造演化历程、沉积充填特征、构造成因及其空间分布规律、构造变形特征等的研究,提出了中国前陆盆地构造地质发育的5个主要特征:(1)两种不同性质的原型盆地发生正反转的叠合性,即挤压构造下作为“本体”的前陆层序与拉张构造下作为“基础”的裂谷、断陷盆地之间的叠置;(2)显生宙以来中国大陆先后发生了4期前陆冲断构造演化的多期性,它们分别是加里东晚期、海西晚期、印支期和喜马拉雅晚期;(3)基于小克拉通基底拼贴后在造山带前缘复活再生的继承性,即统一拼合大陆内部的构造变形导致古造山带的复活,在古造山带边缘发育新生代前陆盆地或前陆冲断带;(4)在空间分布上受环青藏高原巨型盆山体系控制发生陆内变形的系统性,在环青藏高原巨型盆山体系内构造变形强度、盆地沉降幅度、盆山耦合程度等从内环向外环依次降低,从古造山带向克拉通方向构造变形强度依次降低,构造变形样式逐渐简单、构造变形时间依次变新;(5)前陆冲断带的构造样式由于受边界力学条件和沉积地层介质作用而具有多变性,存在沉积盖层内脆性变形的断层相关褶皱、造山带前缘韧性变形的基底卷入构造、与走滑构造相伴生的基底卷入的断层相关褶皱、盆地内部塑性变形的盐构造。正是因为上述地质构造的特殊性,决定了油气聚集与分布特征的规律性和复杂性,由此提出了相应的一些构造地质研究与油气勘探工作的建议。     

柴达木盆地及邻区侏罗纪原型盆地恢复及油气勘探前景

侏罗系是柴达木盆地最重要的源储层系之一。通过野外地质、剖面实测、地震解释、显微构造分析等大量系列资料的综合应用与分析,认为研究区自中生代以来,经历了印支期右行逆冲-走滑构造运动、早—中侏罗世伸展运动、早白垩世北西-南东向挤压及新生代南北向挤压运动,它们与早侏罗世至中侏罗世早期(小煤沟组至大煤沟组)在NE向伸展应力场作用下形成的断陷盆地、中侏罗世晚期至晚侏罗世(彩石岭组—洪水沟组)热力沉降坳陷盆地、早白垩世南北向挤压坳陷盆地密切相关。侏罗纪原型盆地发育三类沉积边界,即盆缘不整合边界(缓坡型和陡坡型边界)、盆内正断层边界、后期逆断层改造边界。不同的现存盆地边界类型对原型盆地恢复的作用不同。侏罗纪盆地以东昆仑构造带为界具有"北陆南洋"的古地理格局,柴达木地区的侏罗纪盆地主要发育在沿岸造山带和岛弧带的山前坳陷以及薄弱的柴北缘加里东俯冲碰撞带之上,形成相对分隔的独立盆地群。柴达木早、中、晚侏罗世原型盆地的分布因受到古特提斯洋向北偏东方向的俯冲作用和阿尔金断裂左旋走滑作用的影响,其沉积中心和沉积范围呈现出从早到晚向东北方向逐渐迁移的规律。早侏罗世盆地的沉积沉降中心主要位于柴北缘西部的冷湖—马海一带,中侏罗世盆地的沉积沉降中心主要位于柴北缘中段的大柴旦—怀头他拉一带,而晚侏罗世盆地的沉积沉降中心主要位于德令哈—乌兰一带。     

Oligo-Miocene extension in the Lycian orogen: evidence from the Lycian molasse basin,SW Turkey

The Lycian molasse basin of SW Turkey is a NE-SW-oriented basin that developed on an imbricated basement, comprising the allochthonous Mesozoic rocks of the Lycian nappes and Palaeocene-Eocene supra-allochthonous sediments. The imbricated basement has resulted from a complex history related to the emplacement of different tectonic units from Late Cretaceous to Late Eocene. Following imbrication, extensional collapse of the Lycian orogen resulted in extensive emergent areas, some of which coincide with present-day mountains. These were surrounded by interconnected depressions, namely, the Kale-Tavas, Çardak-Dazk?r? and Denizli subbasins.

The Lycian molasse sequence contains a relatively complete record of the tectonic history of the Lycian orogenic collapse from which it was derived. The sequence is characterised by interdependence between tectonism and sedimentation, the latter of which includes fining-and coarsening-upward sedimentary cycles with syn-depositional intrabasinal unconformities.

The Denizli subbasin consists of thick, coarse-grained wedges of alluvial fans and fine-grained fan-delta deposits formed in a shallowmarine environment. Some areas of the fan deltas were colonised by corals, red algae and foraminifera, forming patch reefs.

The first phase of extensional collapse in the region is marked by the Lycian orogenic collapse, which may have been initiated by the beginning of the Oligocene (Rupelian), following the main Menderes metamorphism. Starting in the latest Early Miocene or in the Middle Miocene, the area of the molasse basin was subject to deformation with the Lycian nappes, and to erosion as well. At that time, the Lycian nappes, with some ophiolitic assemblages, were thrust over the molasse deposits and thus, NE-SW-trending folds were formed. The molasse deposits and thrust-related deformational structures were then unconformably covered by Upper Miocene continental deposits which belong to the neotectonic period of SW Turkey. The second phase of extensional collapse is marked by granitic intrusions and the formation of Miocene detachment-related extensional basins. This phase may have been related to the exhumation of the gneissic core of the Menderes Massif, from which fragments were derived and incorporated into the upper parts of the Denizli subbasin during the Aquitanian.     

Identification of an underfilled foreland basin system in the Upper Devonian of the Central Pyrenees: implications for the Hercynian orogeny

A foreland basin succession has been identified in the Frasnian of the Central Pyrenees. This succession comprises a carbonate-dominated transgressive system which recorded the cratonward migration of the foreland basin subsidence, and siliciclastic depocenters which recorded the progression of the thrust-fold deformation. The foreland basin system has always been maintained in deep-marine environments, i.e., at an underfilled depositional state. It was associated with a thrust wedge which descended toward a deep-marine hinterland, i.e., with a type of orogenic wedge usually related to subduction zones. The Frasnian foreland basin system differs from the one known in the Carboniferous which evolved to overfilled depositional state and was associated with a thrust wedge rising toward a mountainous hinterland. Consequently, the Hercynian orogeny in the Pyrenees seems to result first, from a Frasnian thrusting controlled by a subduction zone located north of the Pyrenees, and second, from a Carboniferous thrusting controlled by the surrection of a frontal thrust belt in the Pyrenees. The association of underfilled foreland basin systems and hinterland-dipping thrust wedges, as exemplified in the Frasnian of the Pyrenees, can be interpreted as illustrative of the initial stages of thrust-wedge growth in deep-marine settings.     

循化-化隆盆地晚白垩世以来盆山耦合过程: 来自物源与磷灰石裂变径迹年代学分析的证据

循化-化隆盆地新生代沉积及盆地基底和周缘山系磷灰石裂变径迹年代学分析揭示了青藏高原东北缘晚白垩世以来经历过3期隆升剥露事件: (1)盆地基底及拉脊山和西秦岭北缘构造带磷灰石裂变径迹年龄分析普遍记录了晚白垩世-始新世中期相对快速的区域性的隆升剥露事件, 西秦岭北缘快速抬升的起始时间为84Ma, 受控于向北的逆冲抬升; 向北到循化-化隆盆地中部的拉目峡抬升的起始时间为69Ma; 更北的拉脊山一带快速抬升期主要为40~50Ma, 从而反映晚白垩世-始新世中期的快速抬升由南向北逐渐扩展.这一期构造隆升事件导致循化-化隆盆地和临夏盆地缺失了北部西宁-民和盆地古近纪所具有的西宁群沉积.隆升剥露结束于31Ma左右, 此时化隆-循化盆地向东与同时期的临夏盆地相连为一个统一的大型西秦岭山前盆地, 两者具有相同的构造、沉积演化史, 因此循化-化隆盆地他拉组底部地层年龄最老不会超过临夏盆地最老地层的古地磁年龄, 即29Ma.(2)渐新世晚期约26Ma拉脊山开始双向逆冲隆升, 并可能延续到中新世早期约21Ma, 隆升作用使循化-化隆盆地成为挟持于拉脊山逆冲带和西秦岭构造带之间的山前挤压型前陆盆地, 循化-化隆盆地开始大规模沉积巨厚的他拉组冲积扇相粗碎屑岩.(3)通过循化-化隆盆地咸水河组和临夏组的沉积相分析、古流方向和砾石成分分析, 揭示出拉脊山构造带在中新世8Ma左右发生的最大规模的双向逆冲隆升事件, 这次事件直接导致循化-化隆盆地由前陆挤压盆地转变为山间盆地, 形成现今青藏高原东北缘的盆山地貌基本格局.      

晚三叠世龙门山前陆盆地早期(卡尼期)碳酸盐缓坡和海绵礁的淹没过程与动力机制

晚三叠世龙门山前陆盆地分布于扬子克拉通西缘,属于印支期造山楔构造负载驱动的挠曲型前渊凹陷.其中卡尼期马鞍塘组是分布于底部不整合面之上的第一套地层单元,记录了前缘隆起边缘碳酸盐缓坡和海绵礁的构建和淹没过程.据钻孔揭示马鞍塘组的最大厚度超过250m,显示为西北厚东南薄的楔形结构,从北西向南东依次分布了深水盆地、碳酸盐缓坡和海绵礁和浅水滨岸带等沉积物类型.其中碳酸盐缓坡和海绵礁分布于前陆盆地的远端,呈面向西的条带状展布,其走向线与龙门山冲断带的走向大致平行.碳酸盐缓坡和海绵礁的厚度介于30～100m之间,由北西向南东变薄.在垂向上,马鞍塘组由3部分构成,下部为鲕粒滩和生物碎屑滩,中部为海绵礁,上部为黑色页岩,显示为向上变细、变深的沉积序列.在Li et al.(2003)盆地模拟的基础上,本次对卡尼期前陆盆地的沉降速率、沉积速率、海绵礁生长速率、相对海平面上升速率进行了定量计算,其中沉降速率为0.10mm·a-1、沉积速率为0.04mm·a-1、海绵礁生长速率为0.03mm·a-1、相对海平面上升速率介于0.01mm·a-1～0.05mm · a-1之间.研究结果表明:在卡尼期早期,相对海平面处于初始上升阶段,相对海平面上升速率较小,盆地处于欠补偿状态,沉积了碳酸盐缓坡型鲕粒滩和生物碎屑滩;在卡尼期中期,相对海平面上升速率等于海绵礁生长速率,海绵礁持续保持垂直向上的生长状态,形成了高度达100余米的塔礁;在卡尼期晚期,相对海平面上升速率大于海绵礁生长速率,礁顶的水深逐步变大,导致礁体被淹溺致死,从而在卡尼期形成了鲕粒灰岩滩-生物碎屑滩-海绵礁灰岩-页岩的向上变细、变深的沉积序列,显示了前陆盆地早期碳酸盐缓坡和海绵礁生长并被淹没的特有模式.本次研究成果表明龙门山前陆盆地的底部不整合面和碳酸盐缓坡、海绵礁的淹没过程是扬子板块西缘印支期造山楔逆冲构造负载的挠曲变形的产物,显示了在卡尼期松潘-甘孜残留洋盆的迅速闭合和造山楔构造负载向扬子板块的推进过程.