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701.
Siliciclastic and volcaniclastic influences on equatorial carbonates: insights from the Neogene of Indonesia 总被引:5,自引:0,他引:5
ABSTRACT In active tectonic areas of humid equatorial regions, nearshore shallow‐water environments are commonly sites of near‐continuous siliciclastic influx and/or punctuated volcaniclastic input. Despite significant clastic influence, Neogene carbonates developed in SE Asia adjacent to major deltas or volcanic arcs, and are comparable with modern mixed carbonate–clastic deposits in the region. Research into delta‐front patch reefs from Borneo and fore‐arc carbonate platform development from Java is described and used to evaluate the effects of siliciclastic and volcaniclastic influx on regional carbonate sedimentation, local changes in carbonate‐producing biota and sequence development. Regional carbonate development in areas of high siliciclastic or volcaniclastic input was influenced by the presence of antecedent highs, changes in the amounts or rates of clastic input, delta lobe switching or variations in volcanic activity, energy regimes and relative sea‐level change. A variety of carbonate‐producing organisms, including larger benthic foraminifera, some corals, coralline algae, echinoderms and molluscs could tolerate near‐continuous siliciclastic or volcaniclastic influx approximately equal to their own production rates. These organisms adopted various ‘strategies’ for coping with clastic input, including a degree of mobility, morphologies adapted to unstable substrate inhabitation or shedding sediment, and shapes adapted to low light levels. Local carbonate production was also affected by energy regime, clastic grain sizes and associated nutrient input. Clastic input influenced the inhabitable depth range for photoautotrophs, the zonation of light‐dependent assemblages and the morphology and sequence development of mixed carbonate–clastic successions. This study provides data on the dynamic interactions between carbonate and non‐carbonate clastic sediments and, when combined with information from comparable modern environments, allows a better understanding of the effects of siliciclastic and volcaniclastic influx on carbonate production. 相似文献
702.
陕西府谷老高川新第三纪“红层”的划分与时代 总被引:25,自引:6,他引:25
对陕西府谷老高川新第三纪“红层”岩石地层、磁性地层、生物地层的初步研究结果表明,该区上第三系一般含有中新统上部及上新统下部。上中新统地层的时代相当于Turolian的中、晚期,古地磁年龄约为7.4~5.3Ma,其中含有多层哺乳动物化石;下上新统沉积的时代相当于Ruscinian的早、中期,古地磁年龄约为5.3~4.36Ma。二者在岩性、所含动物群的组合及其性质等方面都存在着较大区别。 相似文献
703.
The Upper Miocene and Pliocene evaporite deposits of the Atacama Desert of northern Chile (Hilaricos and Soledad Formations) are among the few non‐marine evaporites in which aridity not only formed the deposits, but has also preserved them almost unaltered under near‐surface conditions. These deposits are largely composed of displacive Ca sulphate and halite together with minor amounts of glauberite, thenardite and polyhalite. However, at the base and top of these deposits, there are also beds of gypsum crystal pseudomorphs that originally formed as free‐growth forms within shallow brine bodies, rather than as displacive sediments. The halite is present as interstitial cement, displacive cubes and shallow‐water, bottom‐growth chevron crusts. Most of the calcium sulphate is presently anhydrite, pseudomorphous after gypsum, that was the primary depositional sulphate mineral. The secondary anhydrite formed under early diagenetic conditions after slight burial (some metres) resulting from the effect of strongly evolved pore brines. The anhydrite has been preserved without rehydration during late diagenetic and exhumation stages on account of the arid environment of the Atacama Desert. Both the Hilaricos and the Soledad Formations contain geochemical markers indicating that these Neogene evaporites had a largely non‐marine origin. Bromine content in the halite is very low (few p.p.m.), indicating neither a sedimentological relation with sea water nor the likelihood of direct recycling of prior marine halites. Moreover, the δ34S of sulphates (+4·5‰ to +9‰) also reflects a non‐marine origin, with a strong volcanic influence, although some recycling of Mesozoic marine sulphates cannot be ruled out. δ34S of dissolved sulphate from hot springs and streams in the area commonly displays positive values (+2‰ to +10‰). Leaching of oxidized sulphur and chlorine compounds from volcanoes and epithermal ore bodies, very common in the associated drainage areas, have been the main contribution to the accumulation of evaporites. The sedimentary and diagenetic evolution of the Hilaricos and Soledad evaporites (based on lithofacies analysis) provides information about the palaeohydrological conditions in the Central Depression of northern Chile during the Neogene. In addition, the diagenesis and exhumation history of these evaporites confirms the persistence of strongly arid conditions from Late Miocene until the present. A final phase of tectonism took place permitting the internal drainage to change and open to the sea, resulting in dissolution and removal of a significant portion of these deposits. Despite the extensive dissolution, the remaining evaporites have undergone little late exhumational hydration. 相似文献
704.
Isaac Casanovas‐Vilar Israel García‐Paredes David M. Alba Lars W. van den Hoek Ostende Salvador Moyà‐Solà 《Journal of Biogeography》2010,37(6):1079-1093
Aim To analyse the diversity dynamics of Miocene mammalian faunas in the Iberian Peninsula in order to determine whether the patterns are related to the dispersal of taxa from other areas into this region. Location Mainly the Iberian Peninsula, but two close geographical areas (Central Europe and the Eastern Mediterranean) are also considered in some of our calculations. Methods Genus‐level faunal lists for a total of 299 localities from the Iberian Peninsula, covering 10 successive biochronological units [Mammal Neogene (MN) zones] that span from the latest Early Miocene to the early Pliocene (about 17–4 Ma), were compiled. The dataset was expanded with a further 331 localities in Central Europe and the Eastern Mediterranean for the same time span. Next, a taxonomically standardized database was used to create composite faunal lists of micro‐ and macromammalian genera present during each MN zone. Separate genera‐by‐MN‐zone matrices for both micro‐ and macromammals were built for each region. Mean standing diversity as well as origination and extinction rates were calculated for the Iberian Peninsula, and their correlation with preservation rates is discussed. Simpson’s coefficient of faunal similarity with Central Europe and the Eastern Mediterranean was calculated in order to evaluate whether diversity patterns were related to changes in the affinity of the Iberian mammalian faunas with those of other regions. Results Diversity changes in the Iberian macromammalian faunas coincide with periods of increased faunal similarity with other regions, suggesting a relationship to the expansions and contractions of the geographical ranges of the constituent taxa. This pattern is not recognized for micromammals; that is, their diversity trends are not related to changes in geographical ranges. Main conclusions Climatic shifts result in expansions or contractions in the geographical ranges of macromammals, owing to changes in the distribution of their preferred habitats. The lower dispersal ability of micromammals results in a higher extinction risk when habitat fragmentation confines their populations to relatively small environmental patches. Hence, they are more severely affected by climatic changes. Our results thus emphasize the role of climatic forcing in mammalian biogeography and diversity. 相似文献
705.
706.
A summary of the present knowledge ofBolboforma is presented in this paper. The genusBolboforma contains a diverse group of marine, mostly single-chambered enigmatic microfossils (phytoplankton, possibly Chrysophyta)
which produced calcitic monocrystalline spheroidal tests with or without inner cysts and with various types of ornamentation.
The genusBolboforma occurs in the time interval between late Early Eocene to Late Pliocene, at middle and higher latitudes, and thus, has not
been recorded in Quaternary to Recent Sediments. The genus is represented globally, but the first and the last occurrence
of the genus appear to be spatially diachronous in both hemispheres.Bolboforma started in the southern hemisphere at the Campbell Plateau (SW Pazific) during the Early Eocene approximately 53 Ma ago,
and the genus lived there until latest Miocene times (5.3 Ma at the Kerguelen Plateau, Southern Indian Ocean). The first occurrence
ofBolboforma in the northern hemisphere is observed in Upper Eocene Sediments (ca. 36.5 Ma) in the Labrador Sea (North Atlantic), and
its youngest occurrence is observed in the Hatton-Rockall Basin (North Atlantic) in the Late Pliocene at 2.84 Ma. Well established
and common species permit the definition of nineteenBolboforma zones/subzones. Not all of these are observed in both hemispheres. In the southern hemisphere all four Paleogene zones, but
only eight Neogene zones are present, in the northern hemisphere only one Paleogene zone, but fourteen Neogene zones have
been determined.
Bolboforma distribution, which appears to be broadly bipolar in temperate to cool regions at middle to higher latitudes, aso seems to
be linked to the evolution of surface watermasses and their boundaries.
相似文献
707.
中国气藏主要形成、定型于新近纪以来的构造运动 总被引:47,自引:22,他引:25
王庭斌 《石油与天然气地质》2004,25(2):126-132
中国大多数气田最终形成、定型于新近纪-第四纪,它们广泛地分布于各类含气(油)盆地。因此,晚期、超晚期生烃成藏、定型以及气藏受制于新近纪以来构造演化历史是中国天然气带有普遍性的重要特征。中国气藏形成与新近纪以来构造演化历史关系密切,主要体现在:(1)在西部,形成的中国式前陆盆地是中国最主要天然气聚集区之一,为形成众多气田创造了有利条件,也是这些盆地本部气藏主要的形成、定型时期。(2)在中部,是四川盆地所有气田主要的形成、定型时期;在鄂尔多斯盆地促进了靖边至乌审旗地区天然气的进一步富集。(3)在东部,为渤海海域晚期成藏创造了有利的地质条件,也促进了其他盆地(坳陷)一些气藏的形成。(4)在近海海域,既促进了有机成因气藏的快速形成,也促进了无机成因非烃气藏以及无机与有机成因天然气的混源,形成了独具特色的成藏模式。 相似文献
708.
Abstract: A new species of the genus Epiphaxum (family Lithotelestidae) is described and illustrated in detail, and compared to other species. Epiphaxum arbuscula sp. nov. has been collected from Upper Eocene (Priabonian), Upper Oligocene (Chattian) and Lower Miocene (Upper Burdigalian) deposits of the Aquitaine Basin, south-west France. Epiphaxum is a poorly documented genus but its fossil record extends back to the Late Cretaceous; it was previously known only from the Paleocene (Danian). Epiphaxum arbuscula differs from all others species of the genus in the form of its colony. In contrast to the creeping colonies of previously known species, it has branched colonies. It is very common at one Upper Oligocene outcrop from which an assemblage with submarine cave remains has been described. A close relationship between the three extant species (two from the Caribbean Sea and one from the Indo-West Pacific region) and the Paleogene species is also noted. These constitute a group that has not undergone any important morphological changes for the last 65 million years. 相似文献
709.
南海珠江口盆地LH-19-4-1井新近纪有孔虫生物地层研究 总被引:3,自引:1,他引:2
标准化石的末现面(LAD)被广泛用于全球性地层划分和对比,但是,只有像白垩纪与第三纪之间的撞击事件所引起的全球性生物集群绝灭(LAD)才具有全球等时间的性质。标准浮游有孔虫化石带的LAD,可能与白垩纪与第三纪之间的撞击事件所引起的LAD一样、具有全球等时面的性质,所以它可以用于全球地层的划分和对比。依据标准浮游有孔虫带的研究,南海珠江口盆地LH-19-1-1井的岩屑地层(430m-2 630m)一共识别出20个带(N_(22)-N_3)。更新世:N_(22)带(430m-620m);晚上新世:N_(21)-N_(20)带(620m-680m);早上新世:N_(19)-N_(18)带(680m-790m);晚中新世:N_(17)-N_(16)带(790m-1 139m);中中新世:N_(15)-N_8带(1 139m-1 898m);早中新世:N_7-N_4带(1 898m-2 588m);晚渐新世:N_3带(2 588m-2 630m)。它们可以和世界其他地区的地层作准确的对比。 相似文献
710.
ZHONG Jianhu WEN Zhifeng GUO Zeqing WANG Haiqiao GAO Jianbo Earth Resource Information College University of Petroleum Dongying Shandong Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou Guangdong 《《地质学报》英文版》2004,78(3):736-743
Typical reefs in the Paleogene and early Neogene strata of the Qaidam Basin, Tibetan Plateau, China, reveal their internal structures and sedimentation environments and consist mainly of algal reef, stromatolite reef and thrombolite reef with distinct reef structures, fore-reef, back-reef and reef-plateau. The fore-reef is characterized by a combination of pinnacle reef, thrombolite and algal reef. The back reef is composed of stromatolite reef and algal reef. The pinnacle reefs (micro-atoll), most of which are several tens of centimeters in diameter (whereas some exceptionally big ones are over 200 cm in diameter), and several tens of centimeter to 2 m in height, are situated on the far front-edge of the reef; the pinnacle reef is also often of recumbent form with a gravel-filled circular hole in the center. The algal reef is in the form of dome and irregular beds, and filled with algal detritus, ostracodes, spirorbis fossils, ooid and terrigenous debris, and worm traces; cavities and scour marks are of 相似文献