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1.
Sedimentary facies and sequence stratigraphy of the Asmari Formation at Chaman-Bolbol, Zagros Basin, Iran 总被引：1，自引：0，他引：1
Mahnaz Amirshahkarami Hossein Vaziri-Moghaddam Azizolah Taheri 《Journal of Asian Earth Sciences》2007,29(5-6):947-959
The Oligocene–Miocene Asmari Formation of the Zagros Basin is a thick sequence of shallow water carbonate. In the study area, it is subdivided into 14 microfacies that are distinguished on the basis of their depositional textures, petrographic analysis and fauna. Based on the paleoecology and lithology, four distinct depositional settings can be recognized: tidal flat, lagoon, barrier, and open marine. The Asmari Formation represents sedimentation on a carbonate ramp. In the inner ramp, the most abundant lithofacies are medium grained wackestone–packstone with imperforated foraminifera. The middle ramp is represented by packstone–grainstone to floatstone with a diverse assemblage of larger foraminifera with perforate wall, red algae, bryozoa, and echinoids. The outer ramp is dominated by argillaceous wackestone characterized by planktonic foraminifera and large and flat nummulitidae and lepidocyclinidae. Three third-order depositional sequences are recognized from deepening and shallowing trends in the depositional facies, changes in cycle stacking patterns, and sequence boundary features. 相似文献
2.
Stratified cultural remains from the Early Roman/Nabataean to Byzantine periods in the coastal zone of Aqaba, Jordan, and analyses of thirteen sediment cores provide evidence for changes in the depositional environment during the Holocene. The overall trend in subsurface sediments is a basal marine transgressive layer overlain by a regressional sequence of embayment lagoonal sediments identified from microfossil analyses, and backshore pond, alluvium, and eolian deposits until the 1st century B.C., when mudbrick structures appear. Based on two radiocarbon dates, a brackish water coastal embayment formed prior to ca. 5900–5700 B.C. and was subsequently filled by siltation. Local tectonic subsidence along faults of the Dead Sea transform may have helped form the lagoon. Freshwater Candona sp. ostracods found in sand layers in the lagoon facies show signs of having been transported and redeposited. These data indicate that lakes or marshes were likely located inland of the study area. Supporting faunal and floral evidence for wetter climatic conditions, wetland habitats, and extensive water diversion and agricultural terraces has been excavated at late Chalcolithic (4000–3500 B.C.) sites in the Aqaba region (Khalil & Schmidt, 2009 ). By the 8th century B.C., the depositional environment along the coastal plain of Aqaba was dominated by distal alluvial fan and eolian sedimentation and the shoreline had prograded about 400m seaward. The migration of human settlements since the 8th century B.C. from the center of the valley toward the southeast may be driven by the changing course of Wadi Yutim and conditions along the coastal plain. © 2010 Wiley Periodicals, Inc. 相似文献
3.
KRISTIAN SCHONING 《Boreas: An International Journal of Quaternary Research》2001,30(4):290-298
Eighteen sites in middle Sweden with sediments deposited during the brackish phase of the Yoldia Sea have been investigated with respect to the marine calcareous benthic fauna (i.e. foraminifera, ostracods and molluscs) and stable oxygen isotopes. At most sites the sediments consist of varved clay sequences which are correlated to the Swedish Time Scale and dated to the Early Preboreal. A marine benthic fauna has been recorded at 11 sites. The fauna occurs during c. 100 clay-varve years and the total length of the brackish phase is estimated to be 110-190 years. Near the inlet of saline water the fauna was dominated by the foraminifera Elphidium excavatum (Terquem) and further to the east the ostracod Cytheropteron montrosiense (Brady, Crosskey and Robertson) dominated. At shallower depths the fauna occurred during a shorter period owing to the formation of a stratified water column with a low-saline surface water. Very low δ 18 O c values were recorded, i.e. between -9.9‰ and -4.7‰ because of the influence of meltwater from the ice sheet. A different isotope fractionation between the foraminifera E. excavatum and the ostracod C. montrosiense was recorded. 相似文献
4.
《Quaternary International》2003,99(1):75-90
Aliki lagoon is a small lagoon located on the micro-tidal south coast of the Gulf of Corinth, Greece. The sediments of the lagoon recovered in three cores provide a record of late Holocene environmental change, including tectonic subsidence, tsunami layers, and change in local vegetation and sedimentation. Four periods of rapid environmental changes were identified over a 5000-yr-long record. These date from about 4700, 3000, 2500 and 2000 yr BP. Each change is linked to activity on the Egion fault, a deepening of the lagoonal bottom and a rise in relative sea level. Six tsunami events are recorded and have been caused by earthquakes on the Egion fault (three events ∼4700, ∼3000 and ∼2500 BP), Eliki fault (2350±40 yr BP) and two more distal fault ruptures. The vegetation history and pollen zones are similar to those recognised by Jahns (Vegetation Hist. Archaebot. 2 (1993) 187) on the Argive Plain, 100 km southeast of the lagoon. Five successive sedimentological configurations are established in relation to the time frame provided by the tectonic activity: (1) crevasse splay; (2) fresh to brackish water marsh; (3) and (4) brackish to hypersaline “blind” lagoon, and (5) brackish to hypersaline “blind” lagoon or brackish open lagoon. 相似文献
5.
Foraminifera in elevated Bermudian caves provide further evidence for +21 m eustatic sea level during Marine Isotope Stage 11 总被引：1，自引：0，他引：1
Peter J. van Hengstum David B. Scott Emmanuelle J. Javaux 《Quaternary Science Reviews》2009,28(19-20):1850-1860
Two hypotheses have been proposed to explain the origin of marine isotope stage (MIS) 11 deposits in small Bermudian caves at +21 m above modern sea level: (1) a +21 m MIS 11 eustatic sea-level highstand, and (2) a MIS 11 mega-tsunami event. Importantly, the foraminifera reported in these caves have yet to be critically evaluated within a framework of coastal cave environments. After statistically comparing foraminifera in modern Bermudian littoral caves and the MIS 11 Calonectris Pocket A (+21 m cave) to the largest available database of Bermudian coastal foraminifera, the assemblages found in modern littoral caves – and Calonectris Pocket A – cannot be statistically differentiated from lagoons. This observation is expected considering littoral caves are simply sheltered extensions of a lagoon environment in the littoral zone, where typical coastal processes (waves, storms) homogenize and rework lagoonal, reefal, and occasional planktic taxa. Fossil protoconchs of the Bermudian cave stygobite Caecum caverna were also associated with the foraminifera. These results indicate that the MIS 11 Bermudian caves are fossil littoral caves (breached flank margin caves), where the total MIS 11 microfossil assemblage is preserving a signature of coeval sea level at +21 m. Brackish foraminifera (Polysaccammina, Pseudothurammina) and anchialine gastropods (95%, >300 individuals) indicate a brackish anchialine habitat developed in the elevated caves after the prolonged littoral environmental phase. The onset of sea-level regression following the +21 m highstand would first lower the ancient brackish Ghyben-Herzberg lens (<0.5 m) and flood the cave with brackish water, followed by drainage of the cave to create a permanent vadose environment. These interpretations of the MIS 11 microfossils (considering both taphonomy and paleoecology) are congruent with the micropaleontological, hydrogeological and physical mechanisms influencing modern Bermudian coastal cave environments. In conclusion, we reject the mega-tsunami hypothesis, concur with the +21 m MIS 11 eustatic sea-level hypothesis, and reiterate the need to resolve the disparity between global marine isotopic records and the physical geologic evidence for sea level during MIS 11. 相似文献
6.
Akram El Kateb Claudio Stalder Christoph Neururer Robin Fentimen Jorge E. Spangenberg Silvia Spezzaferri 《Swiss Journal of Geoscience》2018,111(3):589-606
The eastern edge of the Djerba Island represents an important tourist pole. However, studies describing the environmental processes affecting this Island are scarce. Although never studied before, the peculiar Djerba lagoon is well known by the local population and by tourists. In July 2014, surface sediment and seawater samples were collected in this lagoon to measure grain size, organic matter content and living foraminiferal assemblages to describe environmental conditions. Seawater samples were also collected and the concentration of 17 chemical elements were measured by ICP-OES. The results show that a salinity gradient along the studied transect clearly impacts seagrass distribution, creating different environmental conditions inside the Djerba lagoon. Biotic and abiotic parameters reflect a transitional environment from hypersaline to normal marine conditions. Living benthic foraminifera show an adaptation to changing conditions within the different parts of the lagoon. In particular, the presence of Ammonia spp. and Haynesina depressula correlates with hypersaline waters, whilst Brizalina striatula characterizes the parts of the lagoon colonized by seagrass. Epifaunal species, such as Rosalina vilardeboana and Amphistegina spp. colonize hard substrata present at the transition between the lagoon and the open sea. 相似文献
7.
Outcrop and microscopic studies have been applied in this research paper in order to find out the Asmari Formation depositional sequences in the Shajabil Anticline section located at the north of the Izeh Zone,Zagros Basin,Iran.Five depositional sequences were identified based on 11 facies types （bioclast Nummulitidae Lepidocyclinidae packstone,bioclast perforate foraminifera Nephrolepidina Miogypsinoides wackestone-packstone,bioclast perforate foraminifera Corallinacea wackestone-packstone,bioclast echinoid Neorotalia Brachiopoda wackestone-packstone,coral floatstone-rudstone,bioclast Corallinacea imperforate foraminifera wackestone-packstone,bioclast imperforate foraminifera Archaias wackestone-packstone,bioclast imperforate foraminifera Dendritina wackestone-packstone-grainstone,bioclast imperforate foraminifera Borelis wackestonepackstone and very fine sandy mudstone） corresponding to the tidal flat,restricted and semirestricted lagoon and open marine environments of an inner and middle shelf areas.Well-exposed outcrop horizons of Thalassinoides at the study section are a favorable tool for the regional outcrop sequence stratigraphy.Thalassinoides is considered as an outcrop key-bed for recognition of the Rupelian-Chattian maximum flooding depositional sequence.Coral remnants （small colonies） in outcrop exposures also are associated with the HST depositional sequence （Chattian） for the Asmari Formation.The most important achievement of this research is use of associated maximum flooding surfaces （Pg30,Pg40,Pg50,Ngl0 and Ng20） in the Arabian plate.These maximum flooding surfaces could be recorded as an isochrones surface. 相似文献
8.
山西沁水盆地上石炭统—下二叠统太原组含有重要的可采煤层和煤层气资源,并在该盆地东南部陵川县附城镇一带出露良好露头。基于对太原组露头剖面和部分钻孔资料的研究,综合分析了该组的岩性、沉积构造、实体化石、遗迹化石和沉积序列等沉积特征。(1)太原组灰岩形成于正常浅海(开阔台地)和局限海湾(局限台地)2种沉积环境,其中,L1灰岩顶部、L2灰岩中下部、L4灰岩上部、L5灰岩顶部、L7灰岩顶部和L8灰岩形成于局限海湾环境,其他灰岩层均形成于正常浅海环境;(2)根据太原组煤系岩性组合特征,划分出6个岩性段,各段中的碎屑岩及所含煤层形成于障壁岛(砂岛)、潟湖和潮坪环境中;(3)通过对沉积特征和沉积序列的分析,识别出11种沉积序列类型,提出了太原组煤系发育的岛湖潮坪、局限海湾(潟湖)潮坪和滨岸潮坪等3种聚煤环境模式。该成果可为沁水盆地东南部太原组煤及煤层气勘探与开发提供沉积背景方面的重要信息和理论支撑。 相似文献
9.
The shallow marine sedimentary sequence of the Jaisalmer Basin exhibits one of the important and well-developed Tithonian sedimentary outcrops for western India. The ichnology and ichnofabric of the lower part of Bhadasar Formation (i.e., Kolar Dongar Member) belonging to Tithonian age are presented and discussed. The Kolar Dongar Member represents a shallow marine succession that contains 16 ichnotaxa: Ancorichnus ancorichnus, Conichnus conicus, Gyrochorte comosa, cf. Jamesonichnites heinbergi, Imponoglyphus kevadiensis, Laevicyclus mongraensis, Monocraterion tentaculatum, Ophiomorpha nodosa, Palaeophycus tubularis, P. bolbiterminus, Phycodes palmatus, Planolites beverleyensis, Rhizocorallium isp., Rosselia rotatus, R. socialis, and Teichichnus rectus. The ichnofabric analysis divulges five distinct ichnofabrics, each typifying distinct depositional environment within shallow marine conditions. The ichnofabric Ophiomorpha 1 with syn-sedimentary faulting exemplifies high energy conditions typical of lower shoreface environment, whereas the Ophiomorpha 2 ichnofabric typifies upper shoreface environment. The Ancorichnus ichnofabric reflects lower offshore condition of deposition. The high ichnodiversity Ancorichnus–Rosselia ichnofabric is indicative of inner shelf conditions, while low ichno-diversity Teichichnus ichnofabric indicates prevalence of low energy brackish bay environment. Thus, Tithonian Kolar Dongar Member indicates depositional environment ranging from shoreface to offshore to inner shelf and finally to brackish bay environment. 相似文献
10.
The Asmari Formation(a giant hydrocarbon reservoir)is a thick carbonate sequence of the Oligocenee Miocene in the Zagros Basin,southwest of Iran.This formation is exposed at Tang-e-Lendeh in the Fars interior zone with a thickness of 190 m comprising medium and thick to massive bedded carbonates.The age of the Asmari Formation in the study area is the late Oligocene(Chattian)eearly Miocene(Burdigalian).Ten microfacies are defned,characterizing a gradual shallowing upward trend;the related environments are as follows:open marine(MF 8e10),restricted lagoon(MF 6e7),shoal(MF 3e5),lagoon(MF 2),and tidal fat(MF 1).Based on the environmental interpretations,a homoclinal ramp consisting of inner and middle parts prevails.MF 3e7 are characterized by the occurrence of large and small porcelaneous benthic foraminifera representing a shallow-water setting of an inner ramp,infuenced by wave and tidal processes.MF 8e10,with large particles of coral and algae,represent a deeper fair weather wave base of a middle ramp setting. 相似文献
11.
12.
为探讨盘县土城向斜龙潭组物源及沉积环境,对ZK402号孔龙潭组样品进行微量元素及稀土元素测试分析,结果显示:龙潭期的水体为微咸水—半咸水的淡水环境,水体分层不强的厌氧环境—水体分层及底层水体呈现H2S的厌氧环境;泥岩中稀土含量高,源岩主要为钙质泥岩和碱性玄武岩。根据砂岩粒度分析、薄片鉴定、电子探针等综合分析,在龙潭组中识别出三角洲和障壁砂坝—潟湖沉积相以及三角洲前缘、下三角洲平原、上三角洲平原、潮坪、潟湖等亚相,龙潭早、晚期以潟湖相为主,龙潭中期以分流河道和分流间湾广泛发育为特征。 相似文献
13.
晋东南沁水盆地是目前我国进行煤层气勘探开发的主要地区之一，煤层气储层主要分布在石炭系和二叠系，其厚度明显受沉积古地理控制。本文通过对露头及钻井剖面的岩石学和沉积相研究,对该区主要含煤岩系-山西组和太原组进行了岩相古地理和煤储层聚集控制因素分析。太原组以石灰岩、铝土质泥岩、粉砂岩、粉砂质泥岩及砂岩为主，厚度44.90～193.48 m，含多层可采煤层，总厚度0～16.89 m，平均7.19 m。在太原组沉积期，研究区北部发育下三角洲平原相，煤层相对较厚，中部和南部为泻湖相，煤层相对较薄，东南角主要为滨外碳酸盐陆棚相，在晋城一带障壁砂坝相分布区，煤层亦较厚；山西组以砂岩、粉砂岩、泥岩为主，石灰岩仅在局部地区见到，该组厚18.60～213.25 m，含可采煤层1～2层，总厚度0～10.0 m，平均4.20 m，在山西组沉积期，北部以下三角洲平原分流河道相为主，中部和南部以分流间湾相为主，东南部则以河口砂坝相为主，厚煤带都位于中部和南部的三角洲分流间湾地区。总之，太原组富煤地带多与砂岩富集带相吻合，位于北部下三角洲平原和南部障壁砂坝地区，而山西组厚煤带大都位于南部三角洲分流间湾地区。 相似文献
14.
鄂尔多斯盆地中央古隆起东侧奥陶系是海相固体钾盐矿的重要靶区。本文在岩心、测井和地震等资料的基础上,开展了该地区马家沟组中组合(马五~5~马五~(10)亚段)的沉积微相、蒸发岩分布、蒸发岩形成机制和保存条件研究。结果表明:马家沟组中组合总体为局限台地环境,可进一步划分出潮坪、潮缘滩、外潟湖、内潟湖等沉积微相,各微相沿古隆起呈环带状展布,内潟湖是含钾蒸发岩的主要形成环境;内潟湖沉积具有明显的旋回性,马五~6、马五~8、马五~(10)时期为海退蒸发环境,以蒸发岩和白云岩为主,马五~5、马五~7、马五~9时期为海侵环境,以灰岩为主;海退期,向心浓缩作用形成了大型米脂蒸发盐盆,进一步在"深水成盐"机制下沉积了大量厚层含钾蒸发岩系;岩溶地貌与含钾蒸发岩系分布的关系表明含钾蒸发岩系主体分布于岩溶盆地内幕。印支期岩溶作用的强度和深度分析进一步显示古岩溶作用在岩溶盆地范围内基本未破坏到马家沟组中组合的含钾蒸发岩系,具备了钾盐矿的沉积和保存条件。 相似文献
15.
Western Amazonia's landscape and biota were shaped by an enormous wetland during the Miocene epoch. Among the most discussed topics of this ecosystem range the question on the transitory influx of marine waters. Inter alia the occurrence of typically brackish water associated ostracods is repeatedly consulted to infer elevated salinities or even marine ingressions. The taxonomical investigation of ostracod faunas derived from the upper part of the Solimões Formation (Eirunepé; W-Brazil) documents a moderately diverse assemblage (19 species). A wealth of freshwater ostracods (mainly Cytheridella, Penthesilenula) was found co-occurring with taxa (chiefly Cyprideis) usually related to marginal marine settings today. The observed faunal compositions as well as constantly very light δ18O- and δ13C-values obtained by measuring both, the freshwater and brackish water ostracod group, refer to entirely freshwater conditions. These results corroborate with previous sedimentological and palaeontological observations, which proposed a fluvial depositional system for this part of western Amazonia during the Late Miocene. We demonstrate that some endemic, “brackish” water ostracods (i.e., Cyprideis) have been effectively adapted to freshwater conditions. Thus, their occurrence is no univocal evidence for the influence of brackish or marine waters in western Amazonia during the Miocene. 相似文献
16.
北京延庆盆地第四纪早期介形类动物群、古生态及对该区古环境的认识 总被引：2，自引：1，他引：2
据延庆杨户庄等剖面的介形类化石，结合孢粉、有孔虫及延庆盆地的古地磁资料，确定含化石地层为下更新统。通过剖面下部产出的海相介形类、咸水介形美、有孔虫及剖面上部含的有孔虫、咸水介形类、轮藻等化石古生态的分析，认为延庆盆地在早更新世曾通过河道与海洋相通。推断有２个可能的通道：（１）吉永定河、桑干河、妫水河等河流；（２）经过八达岭、军都山的河流．笔者从地层对比确认新构造运动十分强烈．八达岭、军都山等山峦可能是早更新世以来逐渐升高形成的． 相似文献
17.
The biota of the 1.5 Ma period of the Middle Miocene Sarmatian of the Central Paratethys lack stenohaline components. This was the reason to interpret the Sarmatian stage as transitional between the marine Badenian and the lacustrine Pannonian stages. However, our new data indicate that brackish water conditions could not have prevailed. Sarmatian foraminifera, molluscs, serpulids, bryozoans, dasycladacean and corallinacean algae as well as diatoms clearly indicate normal marine conditions for the entire Sarmatian. During the Lower Sarmatian, however, a sea-level lowstand forced the development of many marginal marine environments. During the Late Sarmatian a highly productive carbonate factory of oolite shoals, mass-occurrences of thick-shelled molluscs and larger foraminifera, as well as marine cements clearly point to normal marine to hypersaline conditions. This trend is not restricted to the western margin of the Pannonian Basin System but can be observed in the entire Central and even Eastern Paratethys. 相似文献
18.
Excavations in the Helike Delta on the Gulf of Corinth have brought to light architectural remains from the Early Bronze Age (EBA), Geometric, Classical, Hellenistic, Roman, and Byzantine periods. Borehole results suggest that a lagoon intermittently occupied much of the delta during the Holocene. We discovered a well‐preserved EBA settlement about 1km inland from the present shore, buried under 3 to 5m of fine sediments containing marine, brackish, and freshwater microfossils. A Classical site 130m away, buried under 3m of similar sediments, may have been destroyed by the earthquake and tsunami of 373 B.C., which submerged the city of Helike. Possible tsunami evidence is noted. Although the EBA and Classical sites were both long submerged and buried by lagoonal sediments, tectonic uplift has raised both horizons above sea level. A shallow black clay layer suggests that a marsh covered the Classical and EBA sites in Byzantine times. © 2011 Wiley Periodicals, Inc. 相似文献
19.
Akbar Heidari Asadollah Mahboubi Reza Moussavi-Harami Luis Gonzalez Seyed Ali Moalemi 《Arabian Journal of Geosciences》2014,7(5):1829-1855
The Guri Member is a limestone interval at the base of the calcareous marls of the Mishan Formation. It is the youngest hydrocarbon reservoir of the southeast part of the Zagros sedimentary basin. This Member overlaid siliciclastic rocks of Razak Formation and is overlain by green and gray marls of the Mishan Formation. In order to consider the paleoecology and paleoenvironments of the Lower–Middle Miocene (Guri Member), we have studied biostratigraphy and sequence stratigraphy of the Guri Member based on foraminifer and microfacies in two stratigraphic sections including Dorahi–Homag and Chahestan. A total of 33 genera and 56 species of benthic and planktonic foraminifera were identified in two studied stratigraphic sections. Benthic and planktonic foraminifera demonstrate Aquitanian to Langhian age (Early–Middle Miocene) for this Member at the study area. Studied interval has deposited in four facies association including supratidal, lagoon, coral reef, and open sea on a carbonate ramp. Carbonate rocks of the Guri Member have precipitated in two and three depositional sequences at Chahestan and Dorahi–Homag sections, respectively. Sedimentation of marine carbonates of the Guri Member on siliciclastic deposits reflects a major transgression of sea level at Lower to Middle Miocene that led to creating a new sea in the Zagros basin at that age. Increasing siliciclastic influx along with a sea level fall finally caused burying of the carbonate ramp. Except for the beginning of sedimentation of carbonate at the base of both stratigraphic sections (depositional sequence 1), most of the system tracts are not matched to global sea level curve that reflect local effects of the basin. Distribution of foraminifera suggests precipitation in tropical to subtropical in mesotrophic to oligotrophic and eutrophic to oligotrophic conditions. Based on large benthic foraminifera (porcelaneous large benthic foraminifera and hyaline larger benthic foraminifera), water temperature average was determined between 25 and 30 °C that was confirmed by analyzing oxygen and carbon stable isotopes. Finally, we have utilized achieved data to reconstruction and modeling of paleoecology, paleoenvironments, and sea level changes in the southeast part of the Zagros basin. 相似文献
20.
J. Ignacio Martínez Yusuke Yokoyama Andres Gomez Adriana Delgado Hiroyuki Matsuzaki Esteban Rendon 《Journal of South American Earth Sciences》2010,29(2):214-224
The detailed stratigraphic survey and paleontological study (mollusks, corals, foraminifera and ostracods) of four low-level, ～3 m, marine terrace sections: Punta Canoas, Manzanillo del Mar, Playa de Oro, and Tierra Bomba Island, from the Cartagena region, southern Caribbean, supplemented with 22 radiocarbon dates, reveals that the northern terraces were deposited as parasequences in a clastic depositional system compared to the Tierra Bomba Island succession that was deposited in a carbonate depositional system between ～3600 and ～1700 cal yrs BP. Drier conditions and the southern location of the ITCZ at about 3 ka triggered stronger easterly Trades and more dynamic southwestward sediment drift fed by the Magdalena River mouth, thus promoting the formation of sand spits that ultimately isolated the Cienaga de Tesca coastal lagoon from the Caribbean Sea. Our estimates support the hypothesis that the present position of the terraces is the product of neotectonism rather than a higher 3 ka, sea-level. Upheaval of the terraces varies between ～3.8 mmyr?1 at Punta Canoas and ～2.2 mmyr?1 at Tierra Bomba to ～1.5 mmyr?1 at Manzanillo del Mar and Playa de Oro terraces. Our study corroborates previous contentions on the role of mud diapirism and the dynamics of the Dique Fault as late Holocene upheaval mechanisms. 相似文献