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1.
Stephen Louwye 《Geological Journal》2002,37(1):55-67
Diverse and well‐preserved palynomorph assemblages recovered from the Deurne Sands, a local member of the Upper Miocene Diest Formation near Antwerp, allow the recognition of dinoflagellate cyst biozones defined in the North Atlantic realm (East Coast, USA) and the North Sea region (Nieder Ochtenhausen well, northern Germany). Based on the dinoflagellate cyst assemblages and the calcareous microfossils, the deposition of the Deurne Sands took place at some time during middle to late Tortonian (Late Miocene). These sands can be correlated biostratigraphically with the Dessel Sands in the Campine area of northern Belgium. This correlation demonstrates the existence of two separate and contemporary depositional areas in northern Belgium during early Late Miocene times. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
2.
A stratigraphical and palaeoenvironmental analysis with organic‐walled palynomorphs of the Bolderberg and Diest formations provides new insights in the depositional history during Miocene times at the southern border of the North Sea Basin. The Neogene transgression invaded Belgium from a north–northwestern direction and fully marine sediments were deposited in the northern part of Belgium. The age and the palaeoenvironment of the deposits at the very border of the southern North Sea Basin remained till a few decades ago incomplete. The recovered dinoflagellate cysts, acritarchs and green algae from the Bolderberg Formation in the Wijshagen Borehole indicate a marginal marine depositional environment during late Burdigalian and Langhian times in the eastern Campine area, in contrast to the deeper marine conditions prevailing to the north–northwest. The relative dating of the Bolderberg Formation confirms that maximum flooding occurred during Langhian to early Serravallian times. Deposition apparently took place during the Middle Miocene Climatic Optimum, and ended when the climatic deterioration set in at around 14 Ma. A hiatus spanning ca. 2 Ma separates the Middle Miocene Bolderberg Formation from the Upper Miocene Diest Formation in the eastern Campine area at the border of the North Sea Basin. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
The occurrence of organic-walled dinoflagellate cysts (dinocysts) in the Diest Formation, a largely decalcified succession with a poor fossil content, and in the adjacent strata of Lower Miocene and Lower Pliocene formations, allowed a biostratigraphic evaluation of these deposits and an assessment of the hiatus between the lithostratigraphic units. The Diest Formation was deposited during Tortonian – Messinian times. Dinocyst biozones defined in the North Sea region and the U.S.A. East Coast are recognised within the Diest Formation, although environmental factors seem to have influenced the presence of some key zonal species in the shallow-marine deposits of northern Belgium. The two members of the Diest Formation studied, i.e., the Dessel Sands and the Diest Sands, appear to be strongly diachronous. The depocentre was located in the Campine area during the early Tortonian and shifted to the area north of Antwerp during late Tortonian to Messinian times. The age assessment provides a correlation of the sequence boundaries of Haq et al. (1987) at the top of the Diest Formation with SB 5.5. 相似文献
4.
Cengiz Yetiş Gilbert Kelling Prof. Dr. Sungu L. Gökçen Francois Baroz 《International Journal of Earth Sciences》1995,84(4):794-812
This study describes the lithostratigraphic character of mid-Cenozoic (Oligocene-Pliocene) sequences in different parts of the northeastern Mediterranean area and offers a detailed stratigraphic correlation for this region. The sequences concerned are drawn from the Camardi area (south-central Anatolia), the Adana Basin, the Misis Mountains and the Kyrenia Range (northern Cyprus) and the submerged Florence Rise (west of Cyprus). The stratigraphic relationships identified here indicate the following: (a) Following the middle Eocene (Lutetian) regression there was uplift throughout the entire region; (b) Episodes of fluvial and lacustrine deposition in intramontane settings ensued in most of this region during the late Eocene/early Miocene interval; (c) Following a regionally extensive phase of tectonic compression, major marine transgression commenced in the late Oligocene in northern Cyprus and in the early Miocene in adjacent southern Turkey, with the exception of the Ecemi§ Fault Zone where continental deposition continued; (d) These Oligo-Miocene transgressive sequences comprise a broadly diachronous complex of both shallow and deeper marine facies, including reefal carbonates, littoral clastics, basinal shales and fan-turbidites; (e) Deeper marine Miocene facies persisted longer in the Misis area and in northern Cyprus; (f) A regional regression occurred throughout most of the area during the late Serravallian to Tortonian interval and is marked by the abrupt, locally discordant appearance of extensive shallow marine, deltaic and fluvial deposits; (g) Continued regression in the Messinian led to the formation of significant evaporite deposits in the western and southern parts of the region, but localized uplift of the Misis area is attested by the initial deformation of the Neogene rocks there and the absence of Messinian sediments from this area; (h) In the Pliocene there was extensive emergence of the northern parts of the region interrupted by brief marine incursions. The present-day drainage pattern was established at this time; (i) Marine conditions persisted longer in northern Cyprus, where emergence occurred only in the latest Pliocene. 相似文献
5.
The Puffin Structure is interpreted from high‐quality 3D seismic data as a small multiringed impact structure formed by collision of a meteorite or small asteroid with unconsolidated, water‐saturated shallow‐marine shelf carbonates during the Middle Miocene (mid to late Serravallian). The impact created a dish‐shaped structure about 2.5 km in diameter with annular rings and no central uplift. 相似文献
6.
Electrical resistivity ground imaging (ERGI): a new tool for mapping the lithology and geometry of channel-belts and valley-fills 总被引：1，自引：0，他引：1
Dave Baines Derald G. Smith Duane G. Froese Paul Bauman† Grant Nimeck† 《Sedimentology》2002,49(3):441-449
Efforts to map the lithology and geometry of sand and gravel channel‐belts and valley‐fills are limited by an inability to easily obtain information about the shallow subsurface. Until recently, boreholes were the only method available to obtain this information; however, borehole programmes are costly, time consuming and always leave in doubt the stratigraphic connection between and beyond the boreholes. Although standard shallow geophysical techniques such as ground‐penetrating radar (GPR) and shallow seismic can rapidly obtain subsurface data with high horizontal resolution, they only function well under select conditions. Electrical resistivity ground imaging (ERGI) is a recently developed shallow geophysical technique that rapidly produces high‐resolution profiles of the shallow subsurface under most field conditions. ERGI uses measurements of the ground's resistance to an electrical current to develop a two‐dimensional model of the shallow subsurface (<200 m) called an ERGI profile. ERGI measurements work equally well in resistive sediments (‘clean’ sand and gravel) and in conductive sediments (silt and clay). This paper tests the effectiveness of ERGI in mapping the lithology and geometry of buried fluvial deposits. ERGI surveys are presented from two channel‐fills and two valley‐fills. ERGI profiles are compared with lithostratigraphic profiles from borehole logs, sediment cores, wireline logs or GPR. Depth, width and lithology of sand and gravel channel‐fills and adjacent sediments can be accurately detected and delineated from the ERGI profiles, even when buried beneath 1–20 m of silt/clay. 相似文献
7.
《International Geology Review》2012,54(6):705-729
In the Thrace Peninsula, Neogene units were deposited in two areas, the Enez Basin in the south and the Thrace Basin in the north. In the southwesternmost part of the peninsula, upper lower–lower upper Miocene continental to shallow marine clastics of the Enez Formation formed under the influence of the Aegean extensional regime. During the last stage of the transpressional activity of the NW-trending right-lateral strike–slip Balkan–Thrace Fault, which had controlled the initial early middle Eocene deposition in the Thrace Basin, a mountainous region extending from Bulgaria eastwards to the northern Thrace Peninsula of Turkey developed. A river system carried erosional clasts of the metamorphic basement southwards into the limnic depositional areas of the Thrace Basin during middle Miocene time. Deposition of fluvial, lacustrine, and terrestrial strata of the Ergene Formation, which conformably and transitionally overlie the Enez Formation, began in the late middle Miocene in the southwest part and in the late Miocene in the north‐northeast part of the basin. Activity along the NE-trending right-lateral strike–slip faults (the Xanthi–Thrace Fault Zone) extending from northeast Greece northeastwards through the Thrace Peninsula of Turkey to the southern shelf of the western Black Sea Basin began during the middle Miocene in the northern Aegean, at the beginning of the late Miocene in the southwest part, and at the end of the late Miocene in the northeast part of the Thrace region. Although the Neogene deposits in the Thrace Basin were evaluated as the products of a northerly fault, our data indicate that the NW-trending northerly fault zone became effective only during the initial stage of the basin development. The later stage deposition in the basin was controlled by the NE-trending Xanthi–Thrace Fault Zone, and the deposits of this basin progressively evolved north/northeastwards during the late Miocene. During the late early Miocene–late Miocene interval, extension within the Thrace region was part of the more regional Aegean extensional realm, but from latest Miocene time, it has been largely decoupled from the Aegean extensional realm to the south. 相似文献
8.
Disperse and punctual studies; absence of integration of data ranging from local to regional focus; interpretations based only on lithostratigraphic features; and interpretation of data premised on an allochthonous origin of the Caribbean plate, are some of factors that increase the confusion and uncertainty in understanding the Sinú-San Jacinto Basin. The sedimentary record of Upper Cretaceous to Eocene has been traditionally interpreted as the record of deep-water settings. However, recently these sediments have been related to shallow marine and deltaic settings. Second problematic point is about the deposition environment of the Oligocene to Late Miocene succession. Some studies suggest canyons, turbidites and sediments deposited in deep-water settings. However, recent studies propose deltaic and shallow marine settings. The last stratigraphic problem is related to the controversial fluvial vs. shallow marine interpretations of the Pliocene sediments. Based upon seismic stratigraphic analysis in recent and reprocessed 2D seismic data, integrated with well data, we propose chronostratigraphic charts for the northern, central and southern zones of the Sinú-San Jacinto Basin. Twenty seismic facies based on amplitude, continuity, frequency and geometry of seismic reflectors and twelve seismic sequences were recognized. The seismic stratigraphic analysis in this study suggests that the sediments of Upper Cretaceous to Paleocene/Eocene were associated to continental to shallow marine settings. Lagoons, coastal plain and carbonate platform dominated during this period. The Oligocene to Middle Miocene record was characterized by deep-water deposition, whereas the Late Miocene to recent sedimentation was characterized by falling base level, characterized by deltaic and fluvial deposits. Five syn-rift sequences with wedge-shaped geometry were identified in this study. Three Triassic to Jurassic syn-rift sequences were characterized by seismic facies typical of fluvial to lacustrine and flood plain sedimentation. Two Cretaceous to Paleocene syn-rift sequences were characterized by seismic facies related to lagoons to coastal plain settings. Normal high-angle faults with a northeast-southwest direction related to rifting processes controlled the development of these sequences. The sheet-drape post-rift section was characterized by passive margin settings in the northern part of the Sinú-San Jacinto Basin and by diachronic tectonic inversion of older normal faults during Cenozoic, predominantly in the central and southern zones. The stratigraphic record related to the Mesozoic to Early Cenozoic rifting; the shallow marine sedimentation during Eocene and the tectono-stratigraphic continuity across the northern Colombia and northwestern Venezuela is coherent and well explained by the in situ origin of the Caribbean plate and is not explained by the “allochthonous” model. 相似文献
9.
《Sedimentary Geology》2005,173(1-4):121-150
The hitherto poorly known Mut basin occupies a position that is critical to our understanding of the later Cenozoic history of south central Turkey. The biostratigraphic and sedimentological study reported here reveals an extended and complex pattern of basin evolution and enables the history of this basin to be compared in detail with that of adjacent south Turkish basins.The oldest basin fill deposits are demonstrated to be Oligocene to earliest Miocene in age and comprise alluvial redbeds, thick lacustrine deposits and thin lagoonal sediments mainly supplied from northern (Tauride) sources This mainly terrestrial megasequence resulted from an early Oligocene phase of crustal extension, leading to rapid “trap-door” subsidence and the formation of narrow E–W trending troughs. This phase was terminated by a minor marine incursion and through reactivation of basement faults during renewed extension in the earliest Miocene.The overlying Miocene succession, thus, rests with local angular discordance upon tilted and gently deformed Oligocene (and older) rocks. Subsequent subaerial erosion created an irregular pre-Burdigalian palaeotopography that strongly influenced the nature, thickness and distribution of the early Miocene basin fill. In palaeotopographic depressions, the Miocene sequence commences with alluvial fan, braidplain and meander belt redbeds formed in river systems that flowed mainly south and southeast. These pass up (and laterally) into more extensive lagoonal and shallow marine mixed clastic/carbonate units yielding late Burdigalian to early Langhian microfaunas, marking the inception of the main Miocene marine transgression in this area. Episodic northwards marine advance led to isolation of the northerly source of siliciclastic detritus and resulted in periodic onlap of mid- to inner-shelf fine-grained carbonates (with thin clastic intercalations) that include isolated coralgal build-ups, calcarenite mounds and sand-waves. At the peak of Miocene transgression (mid-Serravallian), thick reefal limestones were deposited far to the north and also formed on top of basement highs forming the southern and eastern flanks of the basin. Significant influxes of coarse and fine siliciclastics from the north attest to periodic progradational events that are more conspicuous and protracted in the late Serravallian and Tortonian. However, muddy deeper shelf conditions prevailed throughout the middle Miocene in the central part of the basin, while stronger currents and unstable slopes characterise the constricted marine strait in the southeast of the basin near Silifke.In terms of their sequential arrangement, palaeoenvironmental and tectonic evolution the Oligo-Miocene sediments of the Mut basin closely resemble coeval sequences in the adjacent Ecemis–Aktoprak and Karsanti–northern Adana basins and share a similar history, involving complex interplay between regional tectonics and eustasism. Deeper water Oligo-Miocene sequences in the ‘outboard troughs,’ such as the southern Adana basin and the Kyrenia–Misis–Andirin complex, yield more subtle signatures of these tectonic and eustatic events. The differences between these basins are attributable to the influence of regional kinematic elements generated during the reorganisation of plate boundaries in the northeast Mediterranean that followed final suturing of the Arabian and Anatolide plates in the mid-Cenozoic. 相似文献
10.
The Murray Basin in southeastern Australia is a large, shallow, intracratonic basin filled with laterally extensive, undeformed, Cenozoic carbonate and terrigenous clastic sedimentary rocks that constitute regional and locally important groundwater aquifers. The marine Oligo‐Miocene strata distributed throughout the southwestern portion of the basin are here encompassed within the Murray Supergroup. The Murray Supergroup (formerly Murray Group) incorporates the marginal marine marl and clay of the Ettrick Formation, Winnambool Formation and Geera Clay in the western and northern portions of the Murray Basin in South Australia, in addition to the limestone that outcrops along the banks of the River Murray in nearly continuous section for 175 km. The stratigraphic nomenclature of these rocks is revised as follows. The boundary between the lower and upper members of the Mannum Formation is redefined and a new Swan Reach Dolomite Member is erected. The Finniss Clay is revised to Finniss Formation possessing three new members: the Cowirra Clay Member, Portee Carbonate Member and Woolpunda Marl Member. The ‘Morgan Limestone’ is raised to Morgan Group and contains three new formations: the Glenforslan Formation, Cadell Formation (with Murbko Marl Member and Overland Corner Clay Member) and Bryant Creek Formation. The Pata Formation is redefined and described. Type and reference sections are erected for each new and revised unit, and are lithostratigraphically correlated to illustrate their stratigraphic architecture. 相似文献
11.
Peter Wycisk 《International Journal of Earth Sciences》1994,83(4):759-772
The mainly continental deposits of northwest Sudan and south-west Egypt have been correlated with coeval shallow marine and marine deposits in northern Egypt along a north-south running cross-section, based on surface and subsurface data. The palaeodepth curve of northern Egypt illustrates the gradual seal-level rise, reaching its maximum during the Late Cretaceous with conspicuous advances during the Aptian and late Cenomanian. A general highstand is also recorded during the Campanian-Maastrichtian in north-west Sudan. A detailed facies correlation is given for the Aptian and late Cenomanian highstand in western Egypt. The correlation of the Cenomanian Bahariya and Maghrabi formations displays short-term relative sealevel fluctuations. The interpretation illustrates the extensiveness of related erosional processes in the hinterland, partly intensified by temporarily uplift of the Uweinat-Aswan High in the south. Regional uplift and constant erosion took place in south-west Egypt during Coniacian and Santonian times. The regional stratigraphic gaps and uncertain interpretation of the Bahariya Uplift are induced by the influence of the Trans-African Lineament, especially during the Late Cretaceous. Low-stand fluvial sheet sandstones characterized by non-cyclic sequence development and high facies stability occur, especially in the Neocomian and early Turonian. During the Barremian and Albian, fluvial architecture changes to more cyclic fluvial sequences and increasing soil formation, due to increasing subsidence, more humid climatic conditions and the generally rising sea level, culminating in the extensive shallow marine Abu Ballas and Maghrabi formations. 相似文献
12.
祁连山北缘旱峡地区发育完整的下白垩统下沟组-中沟组沉积序列;以陆源碎屑岩为主,发育砾岩、砂岩、钙质粉砂岩和页岩等;其中砾石分选差、磨圆一般、成分以灰白色砂岩为主,砂岩成分、结构成熟度中等-差。岩石组合、沉积序列和综合沉积特征研究表明,下沟组和中沟组主要由湖泊、扇三角洲、河流等3种类型沉积相、亚相与微相类型组成,发育了一系列重力流成因的沉积类型;湖泊沉积主要发育在下沟组底部和中沟组,扇三角洲沉积分布在下沟组中-上部,中沟组发育河流沉积。研究区早白垩世中期古流向以EN向为主,早白垩世晚期以W向为主,表明沉积沉降中心也由早期的旱峡西移至研究区西南侧。在综合分析的基础上,建立了研究区下白垩统下沟组-中沟组沉积相模式。 相似文献
13.
Lower Pleistocene sediments recovered in boreholes from the Aberdeen Ground Formation in the central North Sea indicate that the unit was deposited in a delta front to prodelta/shallow, open shelf marine setting. Possible estuarine and clastic nearshore marine deposits have been identified on the western margin of the basin. The delta front sediments consist of interbedded, structureless to laminated sands and muds with organic debris, ferruginous nodules and common soft sediment deformation structures. Sporadic rippled and graded beds, basal scours to beds and starved ripples suggest periodic wave–current reworking. Prodelta/shelf marine sediments are predominantly argillaceous with only occasional thin sand beds and rare phosphatic bands. One exceptionally thick sand body or submarine channel-fill although this remains uncertain. The estuarine/clastic nearshore marine sediments include coarse channel-lag deposits and rippled and laminated subtidal sands. A rich microfossil assemblage recovered from the prodelta/shelf marine sequence indicates that deposition occurred under fluctuating climatic conditions. 相似文献
14.
《Journal of Asian Earth Sciences》1999,17(3):369-393
Neogene strata of the northern part of the Pegu (Bago) Yoma Range, Central Myanmar, contain a series of shallow marine clastic sediments with stratigraphic ages ranging from the Early to Late Miocene. The studied succession (around 750 m thick) is composed of three major stratigraphic units deposited during a major regression and four major transgressive cycles in the Early to Late Miocene. The transgressive deposits consist of elongate sand-bars and broad sand-sheets that pass headward into mixed-flats of tidal environments. Marine flooding in transgressive deposits is associated with coquina beds and allochthonous coral-bearing sandy limestone bands. Major marine regressions are associated with lowstand progradation of thick estuary point-bars passing up into upper sand-flat sand bodies encased within the tidal flat sequences and lower shoreface deposits with local unconformities. The succession initially formed in a large scale incised-valley system, and was later interrupted by two major marine transgressions in the generally regressive or basinward-stepping stratigraphic sequences. Successive sandbodies were formed during a sea-level lowstand and early stage of the subsequent relative rise of sea level in a tide-dominated estuary system in the eastern part of the Central Myanmar Tertiary Basin during Early to Late Miocene times. 相似文献
15.
《Journal of South American Earth Sciences》2000,13(6):511-525
Permian marine sedimentary rocks that crop out in northern Chile are closely related to the development of a Late Paleozoic magmatic arc. A study of Upper Paleozoic units east of Iquique (20°S) identified three members within the Juan de Morales Formation, each of which were deposited in a different sedimentary environment. A coarse-grained terrigenous basal member represents alluvial sedimentation from a local volcanic source. A mixed carbonate-terrigenous middle member represents coastal and proximal shallow marine sedimentation during a relative sea-level rise related with a global transgression. Preliminary foraminifer biostratigraphy of this middle member identified a late Early Permian (late Artinskian–Kungurian) highly impoverished nodosarid–geinitzinid assemblage lacking fusulines and algae, which is characteristic of temperate cold waters and/or disphotic zone. The upper fine-grained terrigenous member represents shallow marine siliciclastic sedimentation under storm influence. The Juan de Morales Formation consists of continental, coastal and shallow marine sediments deposited at the active western margin of Gondwana at mid to low latitudes. A revised late Early Permian age and similar paleogeography and sedimentary environments are also proposed for the Huentelauquén Formation and related units of northern and central Chile, Arizaro Formation of northwestern Argentina, and equivalent units of southernmost Peru. 相似文献
16.
Francesco Guerrera Mario Tramontana Ugo Donatelli Francisco Serrano 《Swiss Journal of Geoscience》2012,105(3):325-341
The space/time evolution of the Umbria-Romagna-Marche domains of the northern Apennine Miocene foredeep is proposed. In this period, the turbidite siliciclastic sedimentation is represented mainly by the Miocene Marnoso-Arenacea Formation, which generally ends with mainly marly deposits. From the internal Apennine sectors (Umbria-Romagna domain) to the external Adriatic Margin (Marche domain) the siliciclastic succession overlies hemipelagic marly deposits (Schlier Formation). The whole depositional area can be considered as a single wide basin with depocenter or main sedimentation areas progressively migrating eastwards. This basin is characterized by some morphological highs which did not constitute real dams for the sedimentary flows (turbidity currents). Multiple feeding (arkose, litharenites, calcarenites) from different sources is related to palaeogeographical and palaeotectonic reorganization of the most internal, previously deformed, Apennine areas. The activation of the foredeep stage is marked by the beginning of the siliciclastic sedimentation (Late Burdigalian in the most internal sector). This sedimentation ends in the most external sector in the Early Messinian, pointing to a depositional cycle of about 9?C10?Ma. The diachronism of the base of the siliciclastic deposition proves to be almost 5?Ma. The syn-depositional compressional deformation, which shows a marked diachronism, affected the internal area of the foredeep in the Early-Middle Serravallian, and progressively migrated up to Late Miocene, involving more and more external sectors. The deformed siliciclastic sedimentary wedge constitutes an orogenic pile incorporated in the Apennine Chain, represented by different tectonic elements superimposed by means of NE-vergent thrusts. The main stratigraphic and tectonic events of the Toscana-Romagna-Marche Apennines are presented in a general framework, resulting also in a terminological revision. 相似文献
17.
DENG Tao HOU Sukuan WANG Hongjiang 《《地质学报》英文版》2007,81(5):709-721
The Tunggurian Age was nominated in 1984, and the Second National Commission on Stratigraphy of China formally suggested establishing the corresponding chronostratigraphic unit, the Tunggurian Stage, based on the Tunggurian Age in 1999. The name of this stage comes from a lithostratigraphic unit, the Tunggur Formation, and the stratotype section is located at the Tunggur tableland, 15 km southeast of Saihan Gobi Township, Sonid Left Banner, Inner Mongolia. The Tunggurian Age is correlated to the Astaracian of the European land mammal ages, and they share the same definition of the lower boundary at the base of the paleomagnetic Chron C5Bn.1r with an age of 15.0 Ma. In the Tairum Nor section on the southeastern edge of the Tunggur tableland, this boundary is situated within the successive deposits of reddish-brown massive mudstone of the lower part of the Tunggur Formation, with a distance of 7.6 m from the base of the grayish-white sandstones in the middle part of the section. The Tunggurian is approximately correlated to the upper part of the marine Langhian and the marine Serravallian in the International Stratigraphical Chart. The Tunggurian Stage includes two Neogene mammal faunal units, i.e. NMU 6 （MN 6） and NMU 7 （MN 7/8）. The Tairnm Nor fauna from the Talrnm Nor section corresponds to NMU 6, and the Tunggur fauna （senso stricto） from the localities on the northwestern edge of the Tunggur tableland, such as Platybelodon Quarry, Wolf Camp and Moergen, corresponds to NMU 7. Among the Middle Miocene mammalian faunas in China, the Laogou fauna from the Linxia Basin, Gansu, the Quantougou fauna from the Lanzhou Basin, Gansu, the Halamagai fauna from the northern Junggar Basin, Xinjiang, and the Dingjiaergou fauna from Tongxin, Ningxia correspond to NMU 6. 相似文献
18.
BRIAN JONES 《Sedimentology》1992,39(5):857-876
Caves, fossil mouldic cavities, sinkholes and solution-widened joints are common in the Cayman and Pedro Castle members of the Bluff Formation (Oligocene-Miocene) on Grand Cayman and Cayman Brac because they have been subjected to repeated periods of karst development over the last 30 million years. Many voids contain a diverse array of sediments and/or precipitates derived from marine or terrestrial environs, mineral aerosols, and groundwater. Exogenic sediment was transported to the cavities by oceanic storm waves, transgressive seas, runoff following tropical rain storms and/or in groundwater. At least three periods of deposition were responsible for the occlusion of voids in the Cayman and Pedro Castle members. Voids in the Cayman Member were initially filled or partly filled during the Late Oligocene and Early Miocene. This was terminated with the deposition of the Pedro Castle Member in the Middle Miocene. Subsequent exposure led to further karst development and void-filling sedimentation in both the Cayman and Pedro Castle members. Speleothems are notably absent. The void-filling deposits formed during these two periods, which were predominantly marine in origin, were pervasively dolomitized along with the host rock 2–5 million years ago. The third period of void-filling deposition, after dolomitization of the Bluff Formation, produced limestone, various types of breccia, terra rossa, speleothemic calcite and terrestrial oncoids. Most of these deposits formed since the Sangamon highstand 125 000 years ago. Voids in the present day karst are commonly filled or partly filled with unconsolidated sediments. Study of the Bluff Formation of Grand Cayman and Cayman Brac shows that karst terrains on isolated oceanic islands are characterized by complex successions of void-filling deposits that include speleothems and a variety of sediment types. The heterogenetic nature of these void-filling deposits is related to changes in sea level and climatic conditions through time. 相似文献
19.
通过大量的野外剖面观察和盆地内钻井岩心的详细描述,综合测井资料,从岩石类型、结构、沉积构造、古生物化石及测井曲线响应特征等方面对鄂尔多斯盆地及周缘地区下二叠统太原组和山西组沉积相特征进行了全面分析研究。结果表明,太原组主要发育陆棚、海岸、冲积扇和三角洲等沉积相,海岸沉积相包括障壁岛、潟湖和潮坪沉积,三角洲沉积相可划分为三角洲平原、三角洲前缘和前三角洲沉积。山西组主要发育冲积扇、河流、曲流河三角洲、湖泊和海岸沉积相,其中河流沉积相包括辫状河和曲流河沉积,曲流河三角洲沉积相可划分为曲流河三角洲平原、曲流河三角洲前缘和前三角洲沉积,而湖泊沉积相以浅湖沉积为主,海岸沉积主要为潟湖沉积。太原期,海相沉积占主导,主要分布于银川-榆林北部一线以南广大地区,并且从东西两侧至中部地区由浅海陆棚沉积和滨浅海过渡为潟湖沉积和潮坪沉积,其间发育障壁岛。盆地西北缘发育冲积扇和扇三角洲沉积,北部广大地区以三角洲沉积为主,自北向南依次为三角洲平原和三角洲前缘沉积。山西期,海水从盆地东南部退却,整体演变为海陆过渡相沉积,盆地北部乌达-杭锦旗-鄂尔多斯一线发育冲积扇沉积,向南至靖边一带依次发育辫状河和曲流河沉积,靖边以南至延安以北地区以三角洲平原沉积为主,向南至同心-庆阳一线发育三角洲前缘沉积,盆地南部彭阳-泾阳地区主要为浅湖沉积,再向南发育物源来自南部的三角洲沉积,在东南部武乡-义马一带为潟湖沉积。 相似文献
20.
通过大量的野外剖面观察和盆地内钻井岩心的详细描述,综合测井资料,从岩石类型、结构、沉积构造、古生物化石及测井曲线响应特征等方面对鄂尔多斯盆地及周缘地区下二叠统太原组和山西组沉积相特征进行了全面分析研究。结果表明,太原组主要发育陆棚、海岸、冲积扇和三角洲等沉积相,海岸沉积相包括障壁岛、潟湖和潮坪沉积,三角洲沉积相可划分为三角洲平原、三角洲前缘和前三角洲沉积。山西组主要发育冲积扇、河流、曲流河三角洲、湖泊和海岸沉积相,其中河流沉积相包括辫状河和曲流河沉积,曲流河三角洲沉积相可划分为曲流河三角洲平原、曲流河三角洲前缘和前三角洲沉积,而湖泊沉积相以浅湖沉积为主,海岸沉积主要为潟湖沉积。太原期,海相沉积占主导,主要分布于银川—榆林北部一线以南广大地区,并且从东西两侧至中部地区由浅海陆棚沉积和滨浅海过渡为潟湖沉积和潮坪沉积,其间发育障壁岛。盆地西北缘发育冲积扇和扇三角洲沉积,北部广大地区以三角洲沉积为主,自北向南依次为三角洲平原和三角洲前缘沉积。山西期,海水从盆地东南部退却,整体演变为海陆过渡相沉积,盆地北部乌达—杭锦旗—鄂尔多斯一线发育冲积扇沉积,向南至靖边一带依次发育辫状河和曲流河沉积,靖边以南至延安以北地区以三角洲平原沉积为主,向南至同心—庆阳一线发育三角洲前缘沉积,盆地南部彭阳—泾阳地区主要为浅湖沉积,再向南发育物源来自南部的三角洲沉积,在东南部武乡—义马一带为潟湖沉积。 相似文献