论层序地层与岩石地层单位之间的关系——兼论沉积岩区1∶5万区域地质调查中填制“层序—组图”的双重表示方法

从时空关系出发讨论层序地层学与岩石地层学等分支学科之间的关系。建议采用两类主要地层分类系统的多重地层划分方案,把层序地层单位作为相对独立的辅助性地层单位。简述层序地层单位与岩石地层单位之间的几种关系。把层序地层方法用于山东淄川、文祖幅区调中,提出在沉积岩区１∶５万区调中填制“层序—组图”的双重表示方法     

Lake Winnipeg sediment physical properties: interpretation, composite stratigraphic sections and calibration of acoustic reflection profiles

High resolution sediment physical properties, measured on gravity and piston cores collected during cruises to Lake Winnipeg, include bulk density, acoustic velocity, magnetic susceptibility, shear strength and colour reflectance. The high resolution data are used here to construct complete stratigraphic (composite) sections of Lake Winnipeg sediments from a series of individual, discontinuous cores for the North and South Basins. These composite sections are used to evaluate basin-wide glacial and post-glacial depositional histories and to compare the northern and southern basin histories. In addition, these sections provide a baseline depth reference for interpretation of the biostratigraphy, paleomagnetic record and rock magnetic stratigraphy. Some of the data (density and shear strength) are also be used to estimate sediment stress history for the two major lithostratigraphic units and their variations across the basin.     

南秦岭勉略古缝合带非史密斯地层和古海洋新知

南秦岭勉略古缝合带是一个构造混杂岩型非史密斯地层区,由不同时代的原地地层系统和异地地层系统的构造岩片构成。泥盆纪—石炭纪硅质岩的常量元素、稀土元素分析结果指示了勉略小洋盆的存在。区域背景分析表明晚震旦世到早寒武世,南秦岭为扬子板块北部边缘的一部分,中、晚寒武世以后开始分裂形成南秦岭裂陷槽。该海槽于中、晚志留世萎缩但未关闭,泥盆纪又进一步开裂逐渐形成大陆边缘裂谷盆地,晚泥盆世后期到早石炭世早期形成一开放小洋盆。早石炭世后期出现洋壳俯冲,从而转化为活动大陆边缘盆地。该洋盆可能持续到二叠纪,并于印支期最终关闭、碰撞和造山。     

Distribution of Carbon and Oxygen Isotopes in theSequence Stratigraphic Framework of the Middle andUpper Proterozoic in the Ming Tombs Area, Beijing

This paper discusses the distribution pattern and geological significance of the carbon and oxygen isotopes (δ13C and δ18O) in the depositional sequences of Gaoyuzhuangian, Yangzhuangian and Wumishanian ages of the established Middle and Upper Proterozoic sequence stratigraphic framework in the Ming Tombs area lying in western Yanshan Mountain of Beijing. Besides, sketchy determination of δ13C and δ18O was also performed for other formations and members. The analytical results show the following: under the condition of clear-water carbonate sediments, δ13C and δ18O, featuring smaller variation of δ13C but larger variation of δ18O, can well delineate the relative change of sea level, which reflects the difference of primary sedimentary settings; in the presence of terrigenous substances, δ13C values vary greatly while δ18O slightly; the carbon and oxygen isotopes show marked changes at sequence boundaries. Besides, particular patterns can be found in regard to the distribution of carbon and oxy     

含煤岩系沉积学和层序地层学研究现状和展望

在对含煤岩系沉积系研究历史进行回顾的基础上,论述了含煤岩系层序地层学方法以及海平面变化与聚煤作用的关系。注重强调分布广泛的厚煤层实际上是在基准面或海平面的抬升过程中堆积的,煤层底面代表海泛面。     

Pleistocene stratigraphy of the Boco Plain,western Tasmania

The Late Devonian‐Early Carboniferous Mansfield Basin is the northernmost structural sub‐basin of the Mt Howitt Province of east‐central Victoria. It is comprised predominantly of continental clastic sedimentary rocks, and is superimposed upon deformed Cambrian to Early Devonian marine sequences of the Palaeozoic Lachlan Fold Belt. This paper documents evidence for synsedimentary deformation during the early history of the Mansfield Basin, via sedimentological, structural and stratigraphic investigations. Repeating episodes of folding, erosion and sedimentation are demonstrated along the preserved western margins of Mansfield Basin, where fold structures within the lower sequences are truncated by intrabasinal syntectonic unconformities. A convergent successor basin setting (an intermontane setting adjacent to, or between major fault zones) is suggested for initial phases of basin deposition, with synsedimentary reverse faulting being responsible for source uplift and subsequent basin deformation. Palaeocurrents within conglomerate units indicate derivation from the west and are consistent with episodic thrusting along basin margin faults providing elevated source regions. Periods of tectonic quiescence are represented by finer grained meandering fluvial facies (indicative of lower regional topographic gradients) which display drainage patterns that appear not to have been influenced by bounding faults to the west. An up‐sequence increase in the textural and compositional maturity of basin sandstones and conglomerates is proposed to be a result of the incorporation of basin fill into ongoing basin deformation, with unstable metapelitic rocks being progressively winnowed from clast populations. Rather than resulting from Carboniferous (Kanimblan) reactivation of extensional structures, as is generally assumed, the deformation observed within the lower units of the Mansfield Basin is suggested here to be essentially syndepositional and at least Late Devonian in age.     

Stratigraphy and correlation of Carboniferous ignimbrites,Rocky Creek region,Tamworth Belt,Southern New England Orogen,New South Wales

Carboniferous (Visean to Westphalian) pyroclastics and lava flows in the Rocky Creek region, used to redefine the base of the Kiaman reversal, are formally defined or redefined and the status of the main formations clarified. These units include the Caroda Formation, containing the Kooringal Dacite, Boomi Rhyolite and Barney Springs Andesite Members; the Clifden Formation with the Wanganui Andesite, Glen Idle Rhyolite, Appleogue Dacite, Bexley Rhyolite, Pine Cliffs Rhyolite and Downs Rhyodacite Members; Rocky Creek Conglomerate with the Hazelvale Rhyodacite, Mt Hook Rhyolite, Darthula Rhyodacite and Pound Rock Rhyodacite Members; and Lark Hill Formation with the Eulowrie Pyroclastic, Tycannah Rhyodacite and The Tops Rhyolite Members; a number of informal units are also described. The restriction of most volcanic units to one of the three thrust blocks (Boomi, Kathrose and Darthula blocks) of the Rocky Creek region, suggests their current relationships reflect either shortening due to overthrusting or an original distribution affected by depositional or erosional processes. A westerly increase in the proportion of ignimbrites indicates nearness to sources in that direction. Intermediate volcanism, largely confined to southern and central parts of the Boomi block in the east, began in the Visean and ended in the early Namurian. Acid volcanism also began in the Visean in the northern Boomi block but, with the exception of the Peri Rhyolite Member of the Clifden Formation, did not become widespread until later in the Namurian and Westphalian. In contrast, only acid volcanism took place during the early Namurian to Westphalian in the Kathrose and Darthula blocks. Correlations based on AS3 and SL13 SHRIMP dates illustrate a discordance of about 3% when compared with the most likely location for the base of the Kiaman reversal. The bases of both the Rocky Creek Conglomerate and Lark Hill Formation appear to be slightly diachronous.     

Lowstand ramps,fans and deep‐water Palaeoproterozoic and Mesoproterozoic facies of the Lawn Hill Platform: The Term,Lawn, Wide and Doom Supersequences of the Isa Superbasin,northern Australia

The Term, Lawn, Wide and Doom Supersequences represent tectonically driven, second‐order sedimentary accommodation sequences in the Isa Superbasin. The four supersequences are stacked to form two major depositional wedges or packages extending south from the Murphy Inlier onto the central Lawn Hill Platform. A major intrabasin structure, the Elizabeth Creek Fault Zone separates the two depositional wedges. The Term and Lawn Supersequences each form a thick, crudely fining‐upward sedimentary succession. The basal part of each supersequence comprises sand‐dominated facies, deposited under lowstand conditions. The overlying transgressive deposits comprise thick successions of carbonaceous, shale‐prone sediment that represents times of increased accommodation. Synsedimentary fault activity along the northwest‐trending Termite Range Fault and major northeast‐trending faults including the Elizabeth Creek Fault Zone resulted in overthickened sections of parts of the Term and Lawn Supersequences in regional depocentres. A regional extensional event occurred during Wide Supersequence time, and resulted in strike‐slip deformation, uplift and tilting of fault blocks and erosion of underlying Lawn sequences. This tectonic event created small, fault‐bounded depocentres, where basal silty turbidites of the Wide Supersequence are locally thickened. Denudation of fault blocks in the hinterland provided increasing coarse clastic sediment‐supply forming thick, sand‐dominated, lowstand deposits of the upper Wide Supersequence. Overall, the Wide Supersequence exhibits a coarsening‐upwards facies trend. Tectonic quiescence resulted in the accumulation of siltstone‐dominated transgressive and highstand turbidite deposits in mid‐Wide time. The base of the Doom Supersequence comprises thick, feldspathic, debris‐flow sandstones signalling a new provenance. Decreasing accommodation is reflected by coarsening‐ and shallowing‐upwards facies trends in late Doom time. Declining accommodation and the end of sedimentation in the Isa Superbasin were most likely initiated by deformation at the start of the Isan Orogeny.     

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