Evolutionary events of Cainozoic Ostracoda of western Philippine Sea and paleoceanographical implications

The Oligocene ostracod fauna of IISDP Site 292 of the western Philippine Sea was marked by high density, diversity and origination, probably reflecting a favorable period for deep-sea Ostraroda; while the sharp decrease in dtmsity and diversity as well as the repeatedly occurring vxtinctions in thc. Neogene may indicate the deterioration in bottom-water environmcnts at that tlme. Five rriajor faunal changes have been recognized in terms of density, diversity and evolutionary artivity (origination and extinction), occurring in the earliest Oligocene (PI8), mid-Oligocene (P21), earliest Miocene (N4), early Middle Miocene (N8) and late Pliocene (N21). respectively. These changes in ostracod faunas are suggested to represent short-term events related to global paleoceanographical changes and to record the Cainozoic cooling history of the West Pacific Ocean and Philippine Sea deep-water. Project supported by the National Natural Science Foundation of China (Grant No. 49676287).     

A geomorphic framework for understanding the surface archaeological record in arid environments

The Narcao and Cixerri basins in Southwestern Sardinia are east-west trending basins of Oligocene age. Recent geological mapping, combined with structural and stratigraphical analyses, support the proposed hypothesis that these basins were very open growth synclines confined within a structural high, delimited by northwest trending dextral strike slip faults. Previously the basins have been interpreted as fault-bounded grabens. The newer revised interpretation is consistent with the existence of NNW trending dextral strike-slip dynamic, related to a north-south shortening which has generated reverse faulting and tight folds in the underlying, pre-synclinal evolution, Eocene succession. This deformation, along with an interfering sub-orthogonal thrust and fold system which affects the Mesozoic sequence, was traditionally linked to the Pyrenean Orogenesis. The Oligocene–Aquitanian shortening, which resulted in the growth synclines and strike-slip faulting, is consistent with the structural development recognized in north-central Sardinia; there structures related to the collision between continental margins that resulted in the Northern Apennines are well documented. Therefore, the Oligocene tectonics of Southwestern Sardinia also must be related to the collision event between the Southern Europe margin (i.e. a crustal sector corresponding to the future Corsica-Sardinia block) and the Adria Plate, which generated the Northern Apennines. Conversely, the previous E-W shortening- related structures must be related to Pyrenean tectonics.     

Studies of Cainozoic environmental change in Tasmania and coastal East Antarctica: a review

Observational studies on Cainozoic environmental changes in both Tasmania and East Antarctica have led to important modifications in the accepted interpretation of the history of glaciation for each area. Many contributors have played an important role in the processes of investigation leading to the present state of knowledge. A crucial role has been played by the integration of the methods of glacial geomorphology, stratigraphy, sedimentology and dating methods. From studies based on combinations of these approaches, a model of multiple glaciations has been developed to explain observed features in Tasmania. This model is complemented by studies of vegetation history, largely through pollen analysis. A less complete picture of the history of ice‐sheet fluctuations in East Antarctica is beginning to emerge from similar applications of cross‐disciplinary studies.     

Plate kinematics, origin and tectonic emplacement of supra-subduction ophiolites in SE Asia

A unique feature of the Circum Pacific orogenic belts is the occurrence of ophiolitic bodies of various sizes, most of which display petrological and geochemical characteristics typical of supra-subduction zone oceanic crust. In SE Asia, a majority of the ophiolites appear to have originated at convergent margins, and specifically in backarc or island arc settings, which evolved either along the edge of the Sunda (Eurasia) and Australian cratons, or within the Philippine Sea Plate. These ophiolites were later accreted to continental margins during the Tertiary. Because of fast relative plate velocities, tectonic regimes at the active margins of these three plates also changed rapidly. Strain partitioning associated with oblique convergence caused arc-trench systems to move further away from the locus of their accretion. We distinguish “relatively autochthonous ophiolites” resulting from the shortening of marginal basins such as the present-day South China Sea or the Coral Sea, and “highly displaced ophiolites” developed in oblique convergent margins, where they were dismantled, transported and locally severely sheared during final docking. In peri-cratonic mobile belts (i.e. the Philippine Mobile Belt) we find a series of oceanic basins which have been slightly deformed and uplifted. Varying lithologies and geochemical compositions of tectonic units in these basins, as well as their age discrepancies, suggest important displacements along major wrench faults.We have used plate tectonic reconstructions to restore the former backarc basins and island arcs characterized by known petro-geochemical data to their original location and their former tectonic settings. Some of the ophiolites occurring in front of the Sunda plate represent supra-subduction zone basins formed along the Australian Craton margin during the Mesozoic. The Philippine Sea Basin, the Huatung basin south of Taiwan, and composite ophiolitic basements of the Philippines and Halmahera may represent remnants of such marginal basins. The portion of the Philippine Sea Plate carrying the Taiwan–Philippine arc and its composite ophiolitic/continental crustal basement might have actually originated in a different setting, closer to that of the Papua New Guinea Ophiolite, and then have been displaced rapidly as a result of shearing associated with fast oblique convergence.     

Cainozoic heritage in the modern landscape near Bungonia,southern New South Wales

The regional topography of much of the New South Wales Southern Highlands was long attributed to Quaternary erosion, but it has been recently demonstrated that the region was, in fact, well developed by the Eocene. The hillsides at Inverary Park are mantled by the Late‐Eocene Reevesdale Basalt, thus indicating the extent of landscape development by the mid‐Tertiary. Pre‐, intra‐, and post‐basaltic alluvial and lacustrine sediments are compared with the current extent of the basalt, clearly demonstrating the age of this landscape and the paucity of modification since the Late Eocene. Stratigraphic techniques, U/Th, TL and ¹⁴C dating aid reconstruction of much of the Cainozoic history of Inverary Park. Major changes in sediment type and source have long been common, but Late Quaternary changes do not correlate well with similar observations elsewhere, suggesting that changes in hydrologic regime, notably climate change, are not necessarily responsible for changes in the stratigraphic record. This landscape development and preservation is also at odds with most models of landscape development.     

豫西伊川—汝阳地区新生代玄武岩特征及岩浆起源

在豫西伊川—汝阳两县交界地区,出露一套新生代玄武岩。该玄武岩以低硅富碱和钛为特征,属轻稀土元素富集型。玄武岩岩石化学成分比较均一,以碱性橄榄玄武岩为主,微量元素镍和铬含量低,这些特征指示了该玄武岩属上地幔低度部分熔融产生的原生岩浆快速喷出地表的产物。岩浆在上升运移过程中,没有发生明显的分离结晶和同化混染作用,起源于60～85km的上地幔范围。     

台湾省地层多重划分对比研究

台湾省地层多重划分对比研究福建省地矿局台湾省地层研究组（福建省地质矿产局，福州，３５０００３）地层学是地层领域中的基础学科。随着现代地层学和沉积学的发展，地质学家普遍认识到沉积地层叠复是在复杂的侧向堆积过程中形成的，且岩石地层单位具有普遍的穿时性。因...     

Discovery of two ophiolite complexes of different ages in the Khoy area (NW Iran)

New field and laboratory studies on the ophiolite of Khoy (northwestern corner of Iran) lead to the discovery that there are not one, but two ophiolitic complexes in the Khoy area: (1) an old, poly-metamorphic ophiolite, whose oldest metamorphic amphiboles yielded a Lower Jurassic apparent ⁴⁰K–⁴⁰Ar age, and whose primary magmatic age should logically be pre-Jurassic (Upper-Triassic?); (2) a younger non metamorphic ophiolite of well dated Upper Cretaceous age. To cite this article: M. Khalatbari-Jafari et al., C. R. Geoscience 335 (2003).