Potassium‐argon ages on the Cainozoic volcanic rocks of New South Wales

During the Cainozoic there was widespread volcanism, mainly basaltic, in eastern New South Wales. Numerous new K‐Ar ages, together with previously published results, provide information on the age of virtually all the main volcanic provinces, and indicate that the volcanism started about 70 m.y. ago in the Late Cretaceous, and was continuous from about 60 m.y. ago (Palaeocene) until about 10 m.y. ago (middle Miocene). There has been no volcanic activity since 10 m.y. ago.

The ages of uplift of the Eastern Highlands are estimated from the relationship of the dated basaltic flows to the topography. A major uplift is deduced some time between the mid‐Cretaceous and late Oligocene, followed by a quiescent period. A further uplift started some time after the middle Miocene, and it continues to the present day. The highland was uplifted differentially both along and transverse to the axis.     

Nature of late‐Early to Middle Devonian tectonism in the Buckambool area,Cobar, New South Wales

In the Buckambool area, Cobar, New South Wales, the boundary between dominantly shallow‐water, shelf sediments of the Winduck Group and fluviatile sediments of the Mulga Downs Group has been established as a small hiatus not resolvable by available fossil age data. Although dips are parallel over much of the area, disconformable and locally angular unconformable relations are present. This hiatus, late‐Early to Middle Devonian in age, marks a period of uplift, localised folding and erosion. These reflect movement of basement blocks along major fractures that are now revealed as lineaments.

Terminal deformation in the area, reflected by folding and re‐activation of lineaments, postdated deposition of the Mulga Downs Group, and is probably Carboniferous in age.     

Late Tertiary ‘grey billy’ and the age and origin of surficial silicifications (silcrete) in South Australia

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.     

鲁西隆起区晚中生代地层碎屑石榴石分析及物源区构造演化示踪

以鲁西淄博、临朐、平邑、蒙阴盆地为重点研究区,通过盆地中生界砂岩中碎屑石榴石的成分分析,探讨鲁西隆起及周边地区中生代构造演化历史。研究表明,鲁西盆地砂岩中石榴石成分在早中侏罗世和中晚侏罗世期间出现变化,暗示着物源的转变,早中侏罗世时期主要物源是鲁西隆起,中晚侏罗世时期转变为胶东地区和鲁西隆起。侏罗纪时期石榴石的物源转变显示,苏鲁苏鲁造山带可能在中晚侏罗世时期已经抬升至地表。白垩纪鲁西盆地物源主要为胶东地区,鲁西隆起的物源贡献较小,但是青山组中段和王氏组中段物源略有波动。白垩纪鲁西盆地石榴石物源显示,控制鲁西盆地沉积的主要是苏鲁造山带,古地理格架显示东高西低的特征,盆地物源的波动暗示鲁西隆起可能在早白垩世中晚期和晚白垩世中期经历过抬升。     

Quaternary and Holocene coastal uplift in Ikaria Island,Aegean Sea

Abstract

Geomorphological, biological and AMS radiocarbon dating provide evidence of an about lm high elevated palaeo-shoreline at the NE coast of Ikaria Island,Aegean Sea, and to a seismic uplift which occurred after AD950-1150 and was probably responsible for damage in an ancient tower. These data are important for several reasons. They provide evidence for a strong earthquake in an island usually assumed aseismic, coastal uplifts and coastal fauna are scarce in this region, while the Late Holocene uplift correlates with a flight of marine terraces of probably Quaternary age, at least up to 40m high. Long-term uplift is not observed at the footwall of a fault bounding a major graben north of Ikaria, it represents a structural puzzle and it may help to shed some light to the evolution of various extensional terranes.     

Early Uplift History of the Tibetan Plateau:Records from Paleocurrents and Paleodrainage in the Hoh Xil Basin

Paleocurrent indicator data collected in field work were used to study the early Cenozoic regional paleodrainage patterns in the Hob Xil basin in northern Tibetan plateau. The paleocurrent directions of the Eocene Fenghuoshan Group obviously show that the flows were northward with a unidirectional dispersal pattern. This probably reflects the uplift of the Qiangtang terrain during the initial basin deposition period and indicates that the Tanggula Moutains occurred as topographic highlands at least in the Eocene. Paleoflows of the Oligocene Yaxicuo Group were dominantly oriented to the north and then flowed eastwards during its late deposition. This regional variability of paleodrainage patterns of the Yaxicuo Group is interpreted to record the dispersal style of sediments from transverse rivers to longitudinal river systems. It is inferred that the Oligocene uplift of the Kunlun Mountains obstructed by northward paleoflows and created longitudinal river systems parallel to the orogenic belts. The temporal and spatial changes of the paleodrainage patterns suggest that the northern boundary of the Tibetan plateau during the early Cenozoic was situated in the Hoh Xil area and its uplift has progressed northwards through time.     

Late Cainozoic geology,soils, and landscape evolution of the Torrens Creek area,North Queensland

The major features of the geology and geomorphology of the semi‐arid, tropical Torrens Creek area of North Queensland are described. The evolution of the landscape through the late Cainozoic is discussed with reference to three phases of landscape instability and erosion, each separated by phases of stability during which weathering and soil formation proceeded. These erosional periods were probably initiated by episodic uplift of the Great Divide region. Tentative correlations with landscape events in the nearby Nulla Basalt Province suggest that soil profile development probably occurred during late Pliocene (2.3–2.0 m.y. ago), mid‐Pleistocene (1.3–1.1 m.y. ago), and in Quaternary (less than 0.1 m.y. ago) times.     

Grooves and striations on the Stanthorpe Adamellite: Evidence for a possible late Middle ‐ Late Triassic age glaciation

Evidence for glacial erosion of competent intrusive igneous rock is described for sites at Quart Pot Creek, Stanthorpe, Queensland. The bedrock, comprising the Stanthorpe Adamellite, was emplaced during the Early‐Middle Triassic. It is argued that the pluton was exposed during the late Middle ‐ Late Triassic and subjected to glacial erosion at that time. This was consequent to the rapid uplift and denudation of the landscape, which accompanied the Hunter‐Bowen Orogeny. Burial of the eroded surface occurred most probably during that ice age and a subsequent period of subsidence. The ancient surface has been exhumed during more recent denudation. It is suggested that during the late Middle ‐ Late Triassic, climatic conditions remained cold enough over this part of southeastern Australia at least for valley glaciers to form and influence landscape development.     

Geological development of Heard Island,Central Kerguelen Plateau

We report ⁴⁰Ar–³⁹Ar laser step-heating age determinations on 15 stratigraphically controlled lava flows and intrusive rocks from Heard Island, Central Kerguelen Plateau (Indian Ocean). The island history began with uplift of pelagic limestone intruded by 22 Ma gabbro sills. Subaerial and wave erosion levelled the early island, producing an unconformity onto which pillow lavas, tuffaceous sediments and shallow-water, fossiliferous marine siltstone (Drygalski Formation) were deposited, beginning in late Miocene time. Two volcanic systems then formed in the late Quaternary. Big Ben dominates the larger southeast part of the island, while Mount Dixon occupies the northwest Laurens Peninsula. Feeder dykes and the early lava flows in both systems are 400–200 ka. Lava flows with evolved compositions (trachytes, trachyandesites) erupted 100–20 ka. Well-preserved parasitic cones exposed at low elevations are 15–10 ka and younger. Mawson Peak, near the summit of Big Ben, has erupted lava flows as recently as 2007. Heard Island, and nearby active McDonald Island, are subaerial features of a larger Neogene volcanic region of Central Kerguelen Plateau that includes several large sea knolls and recently identified submarine fields of small cones. This broadly distributed volcanic activity is linked to incubation of plume material at the base of the nearly stationary overlying Central Kerguelen Plateau.     

Geomorphic constraints on the Late Neogene tectonics of the Otway Range,Victoria

A Pliocene strandline system in the Hanson Plain Sands, between the volcanic plains of the Western District and the northern flanks of the Otway Range in southwest Victoria, provides an excellent datum against which to measure Late Neogene fault‐related uplift. Individual strandlines that can be traced from elevations of ～120 m near Cobden to ～245 m on the Ferguson Hill structure are displaced across northeast‐trending faults and monoclines associated with the Simpson and Ferguson Hill structures. A break in slope in the Otway Range front at elevations of 230–280 m, beneath which drainage incision parallels the trends of the strandlines, probably correlates with the Pliocene coastline on the ancestral Otway Range. By analogy with correlative systems in the Murray Basin, deposition occurred during sea‐stands between 0 and 65 m above present‐day sea‐level, implying uplift of between 175 and 240 m since the Early Pliocene. Enhanced incision parallel to the strandlines, in combination with tilting of fault blocks about northeast axes at a high angle to the strandlines, has facilitated the development of a remarkable rectilinear drainage net. Local inversion of the drainage where it focused basalt flows constrains the age of incision and faulting to greater than ca 1 Ma and, most probably, less than ca 2 Ma.     

Pliocene and Quaternary regional uplift in western Turkey: the Gediz River terrace staircase and the volcanism at Kula

Along the upper reaches of the Gediz River in western Turkey, in the eastern part of the Aegean extensional province, the land surface has uplifted by 400 m since the Middle Pliocene. This uplift is revealed by progressive gorge incision, and its rate can be established because river terraces are capped by basalt flows that have been K–Ar and Ar–Ar dated. At present, the local uplift rate is 0.2 mm a⁻¹. Uplift at this rate began around the start of the Middle Pleistocene, following a span of time when the uplift was much slower. This was itself preceded by an earlier uplift phase, apparently in the late Late Pliocene and early Early Pleistocene, when the uplift rate was comparable to the present. The resulting regional uplift history resembles what is observed in other regions and is analogously interpreted as the isostatic response to changing rates of surface processes linked to global environmental change. We suggest that this present phase of surface uplift, amounting so far to 150 m, is being caused by the nonsteady-state thermal and isostatic response of the crust to erosion, following an increase in erosion rates in the late Early Pleistocene, most likely as a result of the first large northern-hemisphere glaciation during oxygen isotope stage 22 at 870 ka. We suggest that the earlier uplift phase, responsible for the initial 250 m of uplift, resulted from a similar increase in erosion rates caused by the deterioration in local climate at 3.1 Ma. This uplift thus has no direct relationship to the crustal extension occurring in western Turkey, the rate and sense of which are thought not to have changed significantly on this time scale. Our results thus suggest that the present, often deeply incised, landscape of western Turkey has largely developed from the Middle Pleistocene onwards, for reasons not directly related to the active normal faulting that is also occurring. The local isostatic consequences of this active faulting are instead superimposed onto this “background” of regional surface uplift. Modelling of this surface uplift indicates that the effective viscosity of the lower continental crust beneath this part of Turkey is of the order of 10¹⁹ Pa s, similar to a recent estimate for beneath central Greece. The lower uplift rates observed in western Turkey, compared with central Greece, result from the longer typical distances of fluvial sediment transport, which cause weaker coupling by lower-crustal flow between offshore depocentres and eroding onshore regions that provide the sediment source.     

Character,genesis and tectonic setting of igneous rocks in the Sistan suture zone,eastern Iran

Igneous rocks in the Sistan suture zone have characteristics that can be correlated with important tectonic events. A Late Cretaceous ocean basin is recorded by ophiolites now exposed in numerous mélange zones. Subduction beneath the Afghan block is indicated by Late Cretaceous-Paleocene calc-alkaline volcanics. Collision of the Lut block with the subduction complex in the middle Eocene produced widespread deformation and was followed by the emplacement of late Eocene-early Oligocene calc-alkaline granitic batholiths that probably formed by widespread anatexis of marine sediments. A dominantly Oligocene magmatic event is represented by widespread alkaline volcanics and minor intrusions that appear to be related to major transcurrent faults. Miocene calc-alkaline activity was limited to sporadic volcanism in the north and minor intermediate intrusions farther south. These units are largely underformed and not related to any major faults. The youngest magmatic event is recorded by late Miocene-Pliocene mafic flows that are weakly alkaline, clearly related to right-lateral faults and probably were derived from a deep crustal or upper mantle source.     

Middle Proterozoic uplift events in the Dunbar dome of northeastern Wisconsin,USA

Isotopic ages of granitic and metamorphic rocks exposed in the Dunbar structural dome of northeastern Wisconsin identify a protracted series of tectonic and hydrothermal events that culminated in major regional uplift during Middle Proterozoic (Keweenawan; ca 1,100 Ma) continental rifting and volcanism. The major rock-forming events and the structural development of the dome occurred during the interval 1,862+/–4 Ma to 1,836+/–6 Ma. Whole-rock Rb-Sr ages are partly reset in response to a widely recognized but cryptic event in Wisconsin and Michigan at about 1,630 Ma. The scale and systematic character of the whole-rock resetting strongly suggests the presence of a fluid phase derived in situ from water dissolved in the silicates or externally from a subthrust plate of low-grade metamorphic rocks. The regional nature of the 1,630-Ma disturbance possibly indicates that it is related to a major tectonic event such as an active plate margin far to the south. Rb-Sr biotite ages for the Dunbar dome (this study), the southern complex of the Marquette district (Van Schmus and Woolsey 1975) and the Felch trough area (Aldrich and others 1965) provide a remarkably coherent pattern that reflects multiple episodes of differential uplift. Younger events superimposed on a regional 1,630-Ma imprint are recorded at 1,330 Ma and 1,140 Ma. The 1,330 Ma disturbance could reflect stabilization following intrusion of the Wolf River batholith at 1,485 Ma. The 1,140-Ma uplift event occurred during Keweenawan rifting and volcanism as a result of stresses imposed on a mosaic of fault-bounded blocks with possible subcrustal influence. The remarkably small variance in the 1,140-Ma biotite age peak argues for rapid uplift and cooling, and hence rapid erosion. Detritus from the uplift probably was being shed into nearby tectonic basins most of which did not survive subsequent uplift and erosion.     

TAKE ANOTHER VISION TO THE UPLIFT OF THE QING—ZANG (TIBETAN) PLATEAU BASED ON CENOZOIC VOLCANISM

TAKE ANOTHER VISION TO THE UPLIFT OF THE QING—ZANG (TIBETAN) PLATEAU BASED ON CENOZOIC VOLCANISM     

塔里木盆地古城墟隆起奥陶系多期古流体活动证据及意义

深部热流体活动与碳酸盐岩储层改造及油气成藏具有密切的关系.通过对塔里木盆地古城墟隆起奥陶系的11块样品的成岩观测和流体包裹体系统分析, 识别出3期古流体活动.结合埋藏史, 确定这3期流体活动的发生时间分别为: 第1期以第1世代高角度裂缝及网状裂缝充填方解石为代表, 推测与加里东晚期构造运动有关; 第2期为构造-热液白云岩化流体, 可能与塔里木盆地经历二叠纪末大规模的火山活动有关; 第3期以充填于孔、缝中央的晚期方解石为代表, 记录了晚期天然气充注事件, 发生于喜山期.第1期流体活动伴随的构造运动导致了早期充注的油气沥青化; 第2期流体活动对该区域的储层有建设性改造作用, 所形成的鹰山组内幕储层成为了区内重要的勘探目的层; 第3期流体活动记录了晚期天然气充注事件.因此, 工区应以寻找喜山晚期天然气藏为主要勘探目标.      

中新生代天山地区隆升历史的裂变径迹证据

本文对天山及其两侧盆地的8条典型地质剖面进行了大量的磷灰石裂变径迹测试,重点分析了天山地区不同区域的抬升历史的差异。结果表明天山主要经历4次构造抬升过程,每次抬升的范围并不相同,且存在东西差异:①早白垩世抬升,在天山南北两侧都有发生,且南边抬升早,北边抬升晚。本次抬升导致早中侏罗世天山地区准平原化状态开始解体,盆山分异开始出现;②晚白垩世抬升,从约96Ma开始,天山南侧为盆山同升的区域性隆升,天山北侧的抬升主要发生在东部地区;③古近纪抬升,从约46Ma开始,主要发生在中天山和南天山,造成天山两侧盆地物源区的重大变化,本次抬升为印度-亚洲碰撞在天山地区产生的最早的远程效应;④中新世以来的抬升,从约25Ma开始,主要发生在库车盆地北缘和北天山—准噶尔南缘。从抬升剥蚀量来看,从东向西逐渐变大。     

Anomalously high uplift rates along the Ventura—Santa Barbara Coast, California—tectonic implications

The NW—SE trending segments of the California coastline from Point Arena to Point Conception (500 km) and from Los Angeles to San Diego (200 km) generally parallel major right-lateral strike-slip fault systems. Minor vertical crustal movements associated with the dominant horizontal displacements along these fault systems are recorded in local sedimentary basins and slightly deformed marine terraces. Typical maximum uplift rates during Late Quaternary time are about 0.3 m/ka, based on U-series ages of corals and amino-acid age estimates of fossil mollusks from the lowest emergent terraces.In contrast, the E–W-trending segments of the California coastline between Point Conception and Los Angeles (200 km) parallel predominantly northward-dipping thrust and high-angle reverse faults of the western Transverse Ranges. Along this coast, marine terraces display significantly greater vertical deformation. Amino-acid age estimates of mollusks from elevated marine terraces along the Ventura—Santa Barbara coast imply anomalously high uplift rates of between 1 and 6 m/ka over the past 40 to 100 ka. The deduced rate of terrace uplift decreases from Ventura to Los Angeles, conforming with a similar trend observed by others in contemporary geodetic data.The more rapid rates of terrace uplift in the western Transverse Ranges reflect N—S crustal shortening that is probably a local accommodation of the dominant right-lateral shear strain along coastal California.     

Cenozoic uplift and subsidence in the North Atlantic region: Geological evidence revisited

The topographic evolution of the “passive” margins of the North Atlantic during the last 65 Myr is the subject of extensive debate due to inherent limitations of the geological, geomorphological and geophysical methods used for studies of uplift and subsidence. We have compiled a database of sign, time and amplitude (where possible) of topographic changes in the North Atlantic region during the Cenozoic (65–0 Ma). Our compilation is based on published results from reflection seismic studies, AFT (apatite fission track) studies, VR (vitrinite reflectance) trends, maximum burial, sediment supply studies, mass balance calculations and extrapolation of seismic profiles to onshore geomorphological features. The integration of about 200 published results reveal a clear pattern of topographic changes in the North Atlantic region during the Cenozoic: (1) The first major phase of Cenozoic regional uplift occurred in the late Palaeocene–early Eocene (ca 60–50 Ma), probably related to the break-up of the North Atlantic between Europe and Greenland, as indicated by the northward propagation of uplift. It was preceded by middle Palaeocene uplift and over-deepening of some basins of the North Sea and the surrounding areas. (2) A regional increase in subsidence in the offshore marginal areas of Norway, the northern North Sea, the northern British Isles and west Greenland took place in the Eocene (ca 57–35 Ma). (3) The Oligocene and Miocene (35–5 Ma) were characterized by regional tectonic quiescence, with only localised uplift, probably related to changes in plate dynamics. (4) The second major phase of regional uplift that affected all marginal areas of the North Atlantic occurred in the Plio-Pleistocene (5–0 Ma). Its amplitude was enhanced by erosion-driven glacio-isostatic compensation. Despite inconclusive evidence, this phase is likely to be ongoing at present.     

新生代阿尔金山脉隆升历史的裂变径迹证据

10个片麻岩和花岗岩的磷灰石裂变径迹年龄值位于35.6~13.6 Ma之间,表明了阿尔金山脉的隆升开始于渐新世,并一直延续至中新世.山脉早期的隆升速率较低,后期可能存在一个快速的隆升时期;阿尔金山脉并非整体的均匀隆升,其内分布的NEE走向的断裂也局部控制了山体的隆升;如果山脉的隆升是阿尔金断裂左行走滑的结果,那么可推测阿尔金断裂大型左行走滑的起始时间应为渐新世.区域资料分析表明,青藏高原北缘在渐新世至中新世期间发生了大规模的、区域性的抬升.     

Coarse-grained submarine fan and slope apron deposits in a Cretaceous back-arc basin, Antarctica

The Cretaceous of west James Ross Island, Antarctica represents the proximal fill of a late Mesozoic back-arc basin that was probably initiated by oblique extension during the early development of the Weddell Sea. The succession records sedimentation in two contrasting depositional systems: a laterally persistent slope apron flanking the faulted basin margin interrupted both spatially and temporally by coarse-grained submarine fans. Slope apron deposits are dominated by thinly interbedded turbiditic sandstones and mudstones (mudstone association), interspersed with non-channelized chaotic boulder beds, intraformational slump sheets and isolated exotic blocks representing a spectrum of mass-flow processes from debris flow to submarine gliding. Localized sand-rich sequences (sandstone-breccia association) represent sandy debris lobes at the mouths of active slope chutes. The submarine fan sediments (conglomerate association) are typified by coarse conglomerates and pebbly sandstones, interpreted as the deposits of high-density turbidity currents and non-cohesive debris flows. Three assemblages are recognized and are suggested to represent components of the inner channelled zone of coarse-grained submarine fans, from major fan channels through ephemeral, marginal channels or terraces to levee or interchannel environments. The occurrence of both slope apron and submarine fan depositional systems during the Early and Mid-Cretaceous is attributed to localized input of coarse arc-derived sediment along a tectonically active basin margin. Periods of extensive fan development were probably linked to regional tectonic uplift and rejuvenation of the arc source region; cyclicity within individual fan sequences is attributed to migration or switching of fan channels or canyons. Slope apron sedimentation was controlled largely by intrabasinal tectonics. Local unconformities and packets of amalgamated slide sheets and debris flow deposits probably reflect episodic movement on basin margin faults. Differential subsidence across the basin margin anchored the basin slope for at least 20 Myr and precluded basinward progradation of shallow marine environments.