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1.
Integrated geoscientific datasets have contributed to an understanding of the Tertiary palaeovalleys once draining the Gawler Craton. Systematic investigations of both the shape and depth of the channels are based on interpretations from field exposures, a compendium of geological and drilling data, computer modelling of ancient landscapes, topographic and evaluated digital elevation models, remote sensing imagery, magnetics, seismic, gravity, airborne and transient electromagnetics, and radiometrics. Physical property contrasts that exist between the channel sediments and the underlying bedrock, for example, can be differentiated by geophysical methods to locate the incised‐valley thalweg. Evidence from sedimentology is combined with evidence from other geological and geophysical characteristics to arrive at a general reconstruction of palaeovalley architecture and history. The palaeovalleys were originally incised into the weathered pre‐Tertiary landscape of mostly weathered basement, and Tertiary fluvial, lacustrine, estuarine and even marine sediments accumulated during the Eocene and Miocene. Marine influence extended at least 100 km up the palaeovalleys during at least three major transgressions in the Eocene and Miocene intervals. Major sedimentary phases occurred in the Paleocene to Early Eocene, Middle to Late Eocene, Oligocene to Early Miocene, and Middle Miocene to Early Pliocene times.  相似文献   

2.
A technique for obtaining age estimates for regolith profiles in Australia, based on the oxygen‐isotope composition of the clay mineral assemblage in a profile, is applied to a variety of regolith profiles and kaolinitic sediments from across Australia. Excluding monsoonal regions in the north of the continent, it is possible to distinguish profiles formed in the Late Mesozoic‐Early Tertiary (δ18O values between +15 and +17.5%δō) from profiles formed in post‐mid‐Tertiary times (>+17.5%ō). In addition it is concluded that there remain widespread remnants of a deep‐weathered regolith which developed in pre‐Late Mesozoic (Early Cretaceous or Jurassic?) times when Australia was at high latitude. The low δ18O values associated with clays formed in pre‐Late Mesozoic times (+10 to +15%o) suggest that deep weathering took place in a cool to cold and presumably humid climate, contrary to the traditional belief that deep weathering requires tropical to subtropical temperatures. The formation of deep‐weathered profiles at high latitude in a comparatively cold climate may be linked in part to higher past atmospheric CO2 levels.  相似文献   

3.
鲁西南地区分布着近东西向大致平行排列的早第三纪盆地群。在蒙阴、莱芜盆地早第三纪沉积称为官庄组，在平邑盆地称为卞桥组。依据沉积物特征和沉积旋回都能分为下段、中段和上段。通过对哺乳动物、介形类、轮藻、腹足类和孢粉等化石的研究可确定中段的沉积时代为早始新世，通过对轮藻、介形类和哺乳类动物的研究能确定下段和上段分别为始新世早期和中期。在卞桥组中段和官庄组中段发现介形类Ｃｙｐｒｉｄｅａ属，该属起源于晚侏罗世或早白垩世，在早白垩世繁盛，晚白垩世逐渐衰落，灭绝于晚古新世或早始新世，在早始新世沉积中的发现，是迄今在我国发现的最高层位。  相似文献   

4.
Apatite fission‐track analyses on samples from eastern Sardinia document a complex tectonic history, whose reconstruction is problematic because of the reactivation of faults and structures at different times from Jurassic to Miocene. The oldest ages (150–154 Ma) have been detected on the southern margin of the Gulf of Orosei and are related to the extensional tectonics that characterize the European passive margin during Early and Middle Jurassic times. Thermal modelling of these data allows reconstruction of the burial history of the Mesozoic basin and estimation of a sedimentary thickness of 2000 m. Part of these sediments was eroded during the following uplift, documented by mid‐Cretaceous fission‐track ages. A further exhumation episode of Eocene age has been revealed by fission‐track data on granite samples, and has been inferred to be related to the Alpine orogenic phase. This tectonic episode caused the exhumation of crustal blocks bound by faults that were finally reactivated during the Late Oligocene–Early Miocene.  相似文献   

5.
This paper is a summary of the present knowledge of the Tertiary stratigraphy of Western Australia. Also included is new information on the Cainozoic of the Carnarvon Basin, a result of petroleum exploration in the area.

Tertiary rocks formed during more than one cycle of deposition in three basins (Eucla, Perth, and Carnarvon), and also as thin units deposited in a single transgression along the south coast. The Tertiary stratigraphy of the Bonaparte Gulf Basin is not well known.

Drilling in the Eucla Basin has encountered up to 400 m of Tertiary in the south central part, with uniform thinning towards the margins. The section begins with a middle‐upper Eocene carbonate unit which represents the dominant event in the Tertiary sedimentation in this basin. More carbonates were deposited in the late Oligocene‐early Miocene and middle Miocene.

Along the south coast, the so‐called Bremer Basin, the Plantagenet Group (up to 100 m) of siltstone, sandstone, spongolite, and minor limestone, was deposited during the late Eocene.

The Perth Basin contains up to 700 m of Tertiary sediment, formed during at least two phases of sedimentation. The upper Paleocene‐lower Eocene Kings Park Formation consists of marine shale, sandstone, and minor limestone, with a thickness of up to 450 m. The Stark Bay Formation (200 m) includes limestone, dolomite, and chert formed during the early and middle Miocene. Events after deposition of the Stark Bay Formation are not well known.

The northern Carnarvon Basin and Northwest Shelf contain by far the most voluminous Tertiary sediment known from Western Australia: 3500 m is known from BOCAL's Scott Reef No. 1. A more usual maximum thickness is 2500 m. Most sediments were laid down in four episodes, separated by unconformities: late Paleocene‐early Eocene; middle‐late Eocene; late Oligocene‐middle Miocene; and late Miocene to Recent.

The Paleocene‐early Eocene cycle consists of about 100–200 m (up to 450 m in the north) of carbonate, shale, and marl of the Cardabia Group containing rich faunas of planktonic foraminifera.

The middle‐late Eocene sediments include diverse rock types. Marine and nonmarine sandstone formed in the Merlinleigh Trough. At the same time, the Giralia Calcarenite (fauna dominated by the large foraminifer Discocyclina) and unnamed, deeper water shale, marl, and carbonate (with rich planktonic foraminiferal faunas) formed in the ocean outside the embayment. Thickness is usually of the order of 100–200 m.

The main cycle of sedimentation is the late Oligocene‐middle Miocene, during which time the Cape Range Group of carbonates formed. This contains dominantly large foraminiferal faunas, of a wide variety of shallow‐water microfacies, but recent oil exploration farther offshore has recovered outer continental shelf facies with abundant planktonic foraminifera. A minor disconformity representing N7 and perhaps parts of N6 and N8 is now thought to be widespread within the Cape Range Group. The last part of this cycle resulted in sedimentation mainly of coarse calcareous marine sandstone (unnamed), and, in the Cape Range area, of the sandstone and calcareous conglomerate of the Pilgramunna Formation. Maximum thickness encountered in WAPET wells is 900 m.

After an unconformity representing almost all the late Miocene, sedimentation began again, forming an upper Miocene‐Recent carbonate unit which includes some excellent planktonic faunas. Thickness is up to 1100 m.

Thin marine sediments of the White Mountain Formation outcrop in the Bonaparte Gulf Basin. They contain some foraminifera and a Miocene age has been suggested.  相似文献   

6.

Basalt at Sassafras was erupted in the Middle Eocene. The K‐Ar ages average 45.3 ± 4.9 Ma on whole rock and 48.4 ± 1.9 Ma on plagioclase. The basalt is not limited to a plateau capping, but extends 150 m down into adjacent valleys. Comparison with nearby Eocene basalts shows that there was in excess of 250 m of local relief in the central Shoalhaven valley by the Early Tertiary. The basalts were extruded at high elevation, and denudation of the coastal margin of the upland was already well advanced. Post‐basaltic denudation has been very slow, and the Early Tertiary landscape is well preserved.  相似文献   

7.
A late‐Tertiary age, as well as the commonly accepted mid‐Tertiary age, is proved for widespread silcretes in S.A. This is demonstrated by stratigraphic relationships with palynologically dated sequences, and evidence of erosion of silcretes. The age limits are Early Eocene to Early Miocene and Medial Miocene to Early Pleistocene, probably Late Pliocene. The late‐Tertiary silcrete dominates the duricrusted landscape flanking the north of the Willouran and Flinders Ranges, and forms patches throughout the Tarkarooloo Lobe (Lake Frome area). Silica type varies according to the material cemented; chalcedony and opal are more common in finer grained, less permeable, clayey clastics, and micro‐ to crypto‐crystalline quartz ('grey billy’ or ‘terrazzo') in porous permeable arenites and regoliths.

‘Grey billy’ silcretes with pedogenic features resembling massive nodular calcretes were probably formed close to phreatic surfaces or in the soil zone, and result from deposition of silica and titania from surface waters near ground level. They can be used to mark unconformities. Those without such features were formed at depths of several to tens of metres in the phreatic zone, beyond the effects of a fluctuating groundwater table.

The varying composition of groundwaters and fluctuations of the phreatic surface probably occurred as the result of climatic changes from wet to arid to wet, causing alternate solution and redeposition of silica. Silcrete was essentially a late Mesozoic‐Cainozoic phenomenon, this being a time of general uplift of the Australian continent during intervals of climatic fluctuation. However, the time spans of Australian silcretes are not sufficiently known to make correlations with major climatic events, which are on a finer time‐scale.  相似文献   

8.
In the Northern foreland of Guyana-shield bauxites rest on basement or on Tertiary sediments. They are of Eocene age and represent very porous gibbsite rocks, which are free of quartz and feldspar and which contain only traces of kaolinite. They are covered by Tertiary sediments. The overburden in Guyana consist of the white sands of the Montgomery-Formation and in Surinam of Feldspar bearing sands of the Cosewyne Formation. A late diagenite to epigenetic resilicification which progressed from the bauxite surface into the substratus can be observed at several places in Guyana and Surinam. This resilicification has already been described by Aleva (1965) and by van der Marel (1960 in Montagne 1964). Time and mechanism of this resilification process is of interest. The Eocene foreland bauxite of Surinam and Guyana has been kaolinitizised along joints and fissures upon supply of silicic acid derived from weathering of the sedimentary overburden. At the same time detrial grains of quartz and feldspar have been flushed in from above. The resilicification is thus younger than the sediments on top.  相似文献   

9.
The intra- and epicontinental basins in north-east Africa (Egypt, Sudan) bear ample evidence of weathering processes repeatedly having contributed to the formation of mineral deposits throughout the Phanerozoic.The relict primary weathering mantle of Pan-African basement rocks consists of kaolinitic saprolite, laterite (in places bauxitic) and iron oxide crust. On the continent, the reaccumulation of eroded weathering-derived clay minerals (mainly kaolinite) occurred predominantly in fluvio-lacustrine environments, and floodplain and coastal plain deposits. Iron oxides, delivered from ferricretes, accumulated as oolitic ironstones in continental and marine sediments. Elements leached from weathering profiles accumulated in continental basins forming silcrete and alunite or in the marine environment contributing to the formation of attapulgite/saprolite and phosphorites.The Early Paleozoic Tawiga bauxitic laterite of northern Sudan gives a unique testimony of high latitude lateritic weathering under global greenhouse conditions. It formed in close spatial and temporal vicinity to the Late Ordovician glaciation in north Africa. The record of weathering products is essentially complete for the Late Cretaceous/Early Tertiary. From the continental sources in the south to the marine sinks in the north, an almost complete line of lateritic and laterite-derived deposits of bauxitic kaolin, kaolin, iron oxides and phosphates is well documented.  相似文献   

10.
Differential earth movements occurred during Eocene, Miocene, and late Caino‐zoic times. The faulting formed basins of sedimentation, led to dissection of land‐surfaces in some localities and burial in others, and faulted the Cainozoic sediments.

Laterite and silcrete cap remnants of relict landsurfaces of two different ages. Laterite formed before the Eocene; it was faulted and dissected during the Eocene in the north but continued to develop until the Miocene in the south. Silcrete formed from Eocene to Miocene times; its dissection was promoted by late Cainozoic tectonism.

Since laterite and silcrete formed on the same strata in warm, very moist environments, lithology and climate are not important genetic factors causing laterite to form at one time and silcrete at another. Only base levels of erosion differed. The silcrete surface was largely developed by streams flowing into mid‐Cainozoic lacustrine basins, whereas there is no evidence that these drainage conditions prevailed for laterite formation.  相似文献   

11.
川西高原的上白垩统及第三系   总被引：1，自引：0，他引：1  
刘耕武  李伟同 《地层学杂志》2002,26(3):161-169,205
川西高原的上白垩统及第三系属于山间盆地型陆相沉积 ,红层发育 ,化石稀少 ,地层划分、对比困难。本地区有化石证据的白垩纪地层仅见于雀儿山南麓的德格县 ,错阿组为一套红色含砾砂岩和粉、细砂岩 ,上部夹灰黄、灰黑色钙质粉砂岩及含铜砂岩 ,深灰色含铜砂岩中产有以希指蕨孢居统治地位的孢粉植物群 ,地质时代为晚白垩世中期。本区古近系红层发育 ,理塘县热鲁村附近的热鲁群下部为红色岩系 ,中上部灰黄、灰色粉砂岩内产以 Pali-binia和桃金娘科为主的植物群 ,时代为早—中始新世。目前可以肯定的中新统仅见于松潘县红土坡一带 ,为一套含煤的灰、灰黄色碎屑岩系 ,其中所含的叶化石和孢子花粉表明其时代为中新世。上新统至更新统分布较广 ,北部以白玉县昌台地区较为典型 ,称昌台群。无论从化石或岩性看昌台群均可分为上、下两套 :下部以杂色碎屑岩为主 ,夹砾岩和玄武岩 ,其中的孢粉组合以麻黄及榆科、藜科花粉丰富为特征 ;上部以含褐煤的暗色碎屑岩为主 ,除丰富的植物化石外 ,孢子花粉为松科、菊科、杜鹃科等居优势的组合 ,昌台群的地质时代为上新世到到早更新世。南部的上新统—更新统以昔格达组为代表 ,主要是河湖相暗色岩系 ,局部地区有褐煤夹层 ,产植物叶化石和孢子花粉 ,时代主要属于更新世 ,下部在某  相似文献   

12.
青藏高原北部可可西里盆地第三纪风火山群沉积环境分析   总被引：19，自引：4，他引：19  
青藏高原北部的可可西里盆地是高原腹地最大的第三纪沉积盆地,分布着沉积厚度达 4 782.8m的早始新世-早渐新世风火山群灰紫色砂岩、泥岩和砾岩,其沉积环境演化经历了四个阶段,从早期 56.0～ 52.2Ma河流为主的环境,到中期 52.2～ 4 3.1Ma的湖泊环境和 4 3.1～ 3 8.3Ma的河流与扇三角洲环境,演变到晚期 3 8.3～ 3 2.0Ma河流为主的环境。古水流方向也由北东向变为南东向,到晚期又转变为北向为主,反映盆地沉积中心逐渐向东向北迁移。这种沉积环境演化和盆地沉积中心迁移可能受青藏高原早期隆升的影响.  相似文献   

13.
Augen gneisses, mica schists, and marbles of the Menderes Massif and its sedimentary cover rocks are exposed south of the Gediz graben. The augen gneisses form the structurally lowest part of the studied lithological sequence, and are overlain by a schist complex. The structurally highest part is formed by a series of marbles. The ages of this lithological sequence range from Precambrian to Early Paleocene. Furthermore, this sequence records the tectonic evolution since the Precambrian. The sedimentary cover of the Menderes Massif consists of two groups of sediments from Early Miocene to Quaternary. The lower group, the Alayehir group, consists of Early- to mid-Miocene-aged fluvial and limnic sediments which form the lower and the upper parts, respectively. The Alayehir group is overlain by mainly fluvial sediments of the Gediz group. Both the Alayehir and the Gediz groups are separated by an angular unconformity. Six deformational phases could be distinguished within the metamorphic rocks of the Menderes Massif and its Tertiary cover. The structures which were interpreted to belong to deformational events predating the Paleocene are summarized as deformational phase D1. D1 structures were nearly completely overprinted by the subsequent deformation events. The second deformational phase D2 occurred between Early Eocene and Early Oligocene. D2 occurred contemporaneously with a Barrovian-type regional metamorphism. The third deformational phase D3 is characterized by folding of the axial planes which formed at the end of Early Oligocene. The deformational event D4 occurred during the Late Oligocene and is related to an extensional period. The deposition of the sedimentary rocks which belong to the Tertiary cover of the Menderes Massif that started in the Early Miocene was interrupted by a compressional phase (D5) during the Late Miocene. Sediments which were deposited since the Early Pliocene record structures which were related to a young extensional phase (D6). This extensional phase has continued to the Present.  相似文献   

14.
第三纪的板块运动驱动着澳大利亚的气候和植被进行演化。广布的湿润森林区是澳大利亚老第三纪的特征。一直到始新世 ,生物多样性都在不断地提高。毫无疑问 ,这是澳大利亚由高南纬区向北部中纬区运移的结果。从始新世到上新世 ,澳大利亚的气候总体上要比现在湿润 ,但降水量季节性变化的增强推动了中新世以后硬叶植物和旱生植物的发展。上新世晚期似乎与第四纪一样 ,都出现过周期性干旱。这种干旱与冰期条件有关 ,至少由南澳大利亚晚第四纪的记录可以认识到这一点 ,澳大利亚的这段历史与东亚的气候变迁是同步发生的。在东亚 ,印—澳板块的运动致使青藏高原抬升 ,从而引发了区内乃至全球气候的巨变。穿越赤道区的季风和信风的环流格局 ,致使新第三纪和第四纪中国与澳大利亚的气候系统的相关性更强。  相似文献   

15.
The Cainozoic history of the Lake Eyre region opened with a period of deep weathering during which many of the older rocks were extensively kaolinized. Following erosion and later deposition of a thin sheet of Tertiary fluviatile deposits, a period of weathering resulted in the widespread formation of silcrete. Another period of erosion and deposition was followed by soil formation and minor silici‐fication.

An important period of erosion followed during which some of the main elements of the present landscape were outlined. Warping during this interval gave rise to shallow basins in which lacustrine sediments accumulated. At about the same time, a system of mound springs developed near the western margin of the Great Artesian Basin. Another major period of erosion followed, by which time the main topographic features of the present landscape had evolved. This last event probably took place near the close of the Tertiary. Throughout the Tertiary, drainage was external and ancestral Lake Eyre remained fresh.

The Quaternary was characterized by four periods of aeolian and, to a lesser extent, water erosion and deposition alternating with periods of landscape stability, when weathering and soil formation took place.

Throughout the Cainozoic there was an alternation of relatively humid and dry periods, but true aridity and internal drainage did not appear until the Quaternary. Sand ridges were not formed until the late Quaternary. Intervals of gentle warping occurred from time to time during the Tertiary, but the Quaternary has for the most part been a period of stability. These events have given rise to a sequence of distinctive rock and soil‐stratigraphic units whose characteristics are considered in some detail.  相似文献   

16.
Fifty‐three sea‐floor samples close to Antarctica collected by Douglas Mawson during the Australasian Antarctic Expedition of 1911–1914 have beeen analysed for recycled palynomorphs. The distribution of the recycled microfossils provides a broad guide to the position of hidden sedimentary sequences on the Antarctic continental margin.

The samples were dredged off the East Antarctic coast between 91°E and 146°E. In three distinct ‐areas, concentrations of recycled palynomorphs suggest the presence nearby of eroding sedimentary sequences. Near the western edge of the Shackleton Ice Shelf the recycled suite suggests Early to Late Permian, Late Jurassic to mid‐Cretaceous, and Late Cretaceous to Early Tertiary sediments, with evidence for marine influence only in the Tertiary. Samples from the outer edge of the continental shelf and slope east of Cape Carr indicate Early Cretaceous and Late Cretaceous to Early Tertiary sequences, and the same age span is suggested by samples from the western side of the Mertz Glacier Tongue; in this area radio echosounding has suggested that inland sedimentary basins intersect the coast.

The sedimentary sequence predicted for the Shackleton Ice Shelf area probably faced the open Indian Ocean, at least since the Mesozoic. Cretaceous sequences predicted for the other localities occur at points on the Antarctic coast where they would be expected on the basis of most reconstructions. The area east of Cape Carr has as its conjugate’ coast part of the Great Australian Bight Basin; that off the Mertz Glacier, the area west of the Otway Basin. At both these areas on the southern Australian margin thick Cretaceous rift‐valley sequences occur.  相似文献   

17.
《Sedimentary Geology》2005,173(1-4):15-51
The Ulukışla Basin, the southerly and best exposed of the Lower Tertiary Central Anatolian Basins, sheds light on one of the outstanding problems of the tectonic assembly of suture zones: how large deep-water basins can form within a zone of regional plate convergence. The oldest Ulukışla Basin sediments, of Maastrichtian age, transgressively overlie mélange and ophiolitic rocks that were emplaced southwards onto the Tauride microcontinent during the latest Cretaceous time. The Niğde-Kirşehir Massif forming the northern basin margin probably represents another rifted continental fragment that was surrounded by oceanic crust during Mesozoic time. The stratigraphic succession of the Ulukışla Basin begins with the deposition of shallow-marine carbonates of Maastrichtian–Early Palaeocene age, then passes upwards into slope-facies carbonates, with localised sedimentary breccias and channelised units, followed by deep-water clastic turbidites of Middle Palaeocene–Early Eocene age. This was followed by the extrusion of c. 2000 m of basic volcanic rocks during Early to Mid Eocene time. After volcanism ended, coral-bearing neritic carbonates and nummulitic shelf sediments accumulated along the northern and southern margins of the basin, respectively. Deposition of the Ulukışla Basin ended with gypsum deposits including turbidites, debris flows, and sabkhas, followed by a regional Oligocene unconformity.The Ulukışla Basin is interpreted as the result of extension (or transtension) coupled with subsidence and basic volcanism. After post-volcanic subsidence, the basin was terminated by regional convergence, culminating in thrusting and folding in Late Eocene time. Comparisons of the Ulukışla Basin with the adjacent central Anatolian basins (e.g. Tuzgölü, Sivas and Şarkişla) support the view that these basins formed parts of a regional transtensional (to extensional) basin system. In our preferred hypothesis, the Ulukışla Basin developed during an intermediate stage of continental collision, after steady-state subduction of oceanic crust had more or less ended (“soft collision”), but before the opposing Tauride and Eurasian continental units forcefully collided (“hard collision”). Late Eocene forceful collision terminated the basinal evolution and initiated uplift of the Taurus Mountains.  相似文献   

18.
《Earth》2009,92(1-4):27-76
In this study we reconstruct the evolution of the northern New England passive margin whose development has been influenced by Pleistocene glaciations. The morphology of the northern New England shelf is rather unique consisting of a inner lowland, the Gulf of Maine, with an average depth of 150 m and an area of 90,700 km2 and Georges Bank, a high whose crest is less than 40 m deep and has an area of 27,000 km2. The bank's northern slope, facing the Gulf of Maine, has a maximum relief of 377 m. On the seaward side of Georges Bank is the 2000 m high continental slope deeply cut by canyons. Two channels, Northeast and Great South Channels, east and west of Georges Bank, provide passageways from the Gulf of Maine to the open sea. This morphology was acquired by a combination of Tertiary fluvial erosion, Pleistocene glacial erosion/deposition and Pleistocene/Holocene marine processes. Fluvial/glacial erosion in the Gulf of Maine was so extensive as to expose basement, thus making it possible to map the various terranes making up this foundation. These terranes include the pre-Carboniferous Avalon and Meguma units, a Carboniferous–Permian rift basin formed by the oblique continental collision during the closure of the Paleozoic proto-Atlantic and a Late Triassic–Early Jurassic rift system created during the opening of the present Atlantic. Basement in the Gulf of Maine remained above sea level from the opening of the Atlantic 190 Ma (Early Jurassic) to the Eocene 55 Ma. That the Gulf of Maine remained a high for so long may have been due to igneous activity along the northwest-trending Boston–Ottawa Lineation extending from the vicinity of the St. Lawrence River, Canada to Gulf of Maine from Late Triassic to Early Cretaceous. The northwest-trending New England Seamounts south of Georges Bank may represent a seaward extension of this lineation. On Georges Bank, rising hundreds of meters above the Gulf of Maine, the basement exposed in the gulf is mantled by sediments thousands of meters thick. Included in these sediments are Early Jurassic- to earliest Cretaceous reefs along the continental slope and carbonates north of the reefs grading landward into continental sediments, Cretaceous–Cenozoic continental/marine terrigenous sediments and Pleistocene glacial deposits. The continental slope on the seaward flank of Georges Bank has a complex history of early to mid Mesozoic carbonate accretion, mid to late Mesozoic and Cenozoic calcareous/terrigenous sediments and canyon erosion, burial and exhumation going back to Early Cretaceous.  相似文献   

19.
The Malatya Basin is situated on the southern Taurus-Anatolian Platform. The southern part of the basin contains a sedimentary sequence which can be divided into four main units, each separated by an unconformity. From base to top, these are: (1) Permo-Carboniferous; (2) Upper Cretaceous–Lower Paleocene, (3) Middle-Upper Eocene and (4) Upper Miocene. The Upper Cretaceous–Tertiary sedimentary sequence resting on basement rocks is up to 700 m thick.The Permo-Carboniferous basement consist of dolomites and recrystallized limestones. The Upper Cretaceous–Lower Paleocene transgressive–regressive sequence shows a transition from terrestrial environments, via lagoonal to shallow-marine limestones to deep marine turbiditic sediments, followed upwards by shallow marine cherty limestones. The marine sediments contain planktic and benthic foraminifers indicating an upper Campanian, Maastrichtian and Danian age. The Middle-Upper Eocene is a transgressive–regressive sequence represented by terrestrial and lagoonal clastics, shallow-marine limestones and deep marine turbidites. The planktic and benthic foraminifers in the marine sediments indicate a Middle-Upper Eocene age. The upper Miocene sequence consists of a reddish-brown conglomerate–sandstone–mudstone alternation of alluvial and fluvial facies.During Late Cretaceous–Early Paleocene times, the Gündüzbey Group was deposited in the southern part of a fore-arc basin, simultaneously with volcanics belonging to the Yüksekova Group. During Middle-Late Eocene times, the Yeşilyurt Group was deposited in the northern part of the Maden Basin and the Helete volcanic arc. The Middle-Upper Eocene Malatya Basin was formed due to block faulting at the beginning of the Middle Eocene time. During the Late Paleocene–Early Eocene, and at the end of the Eocene, the study areas became continental due to the southward advance of nappe structures.The rock sequences in the southern part of the Malatya Basin may be divided into four tectonic units, from base to top: the lower allochthon, the upper allochthon, the parautochthon and autochthonous rock units.  相似文献   

20.
The petrography, heavy mineral analysis, major element geochemical compositions and mineral chemistry of Early Cretaceous to Miocene–Pliocene rocks, and recent sediments of the Tarfaya basin, SW Morocco, have been studied to reveal their depositional tectonic setting, weathering history, and provenance. Bulk sediment compositional and mineral chemical data suggest that these rocks were derived from heterogeneous sources in the Reguibat Shield (West African Craton) including the Mauritanides and the western Anti-Atlas, which likely form the basement in this area. The Early Cretaceous sandstones are subarkosic in composition, while the Miocene–Pliocene sandstones and the recent sediments from Wadis are generally carbonate-rich feldspathic or lithic arenites, which is also reflected in their major element geochemical compositions. The studied samples are characterized by moderate SiO2 contents and variable abundances of Al2O3, K2O, Na2O, and ferromagnesian elements. Binary tectonic discrimination diagrams demonstrate that most samples can be characterized as passive continental marginal deposits. Al2O3/Na2O ratios indicate more intense chemical weathering during the Early Cretaceous and a variable intensity of weathering during the Late Cretaceous, Early Eocene, Oligocene–Early Miocene, Miocene–Pliocene and recent times. Moreover, weathered marls of the Late Cretaceous and Miocene–Pliocene horizons also exhibit relatively low but variable intensity of chemical weathering. Our results indicate that siliciclastics of the Early Cretaceous were primarily derived from the Reguibat Shield and the Mauritanides, in the SW of the basin, whereas those of the Miocene–Pliocene had varying sources that probably included western Anti-Atlas (NE part of the basin) in addition to the Reguibat Shield and the Mauritanides.  相似文献   

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