CORUNDUM OF PING SHAN DISTRICT, W. CHIHLI.

I. GEOLOGY AND TOPOGRAPHY OF THE CORUNDUM DISTRTOT. The corundum is found in Ping Shan Hsien (平山縣) which is located in the south-western part of Chihli. It connects with Chin Hsing     

CORUNDUM OF PING SHAN DISTRICT, W. CHIHLI.

I. GEOLOGY AND TOPOGRAPHY OF THE CORUNDUM DISTRTOT. The corundum is found in Ping Shan Hsien (平山縣) which is located in the south-western part of Chihli. It connects with Chin Hsing     

Structural analysis of Bermagui area,N.S.W.

The Ordovician rocks exposed along the N.S.W. coast, near Bermagui, comprise a sequence of alternating greywacke and shale and a less abundant sequence of alternating chert and detrital beds. The only lithological boundary that can be mapped is the contact between the two sequences and it sheds little light on the large scale structure. However, due to continuity of outcrop, well‐defined vergence zones and abundant younging evidence it is possible to interpret the regional structure.

Two generations of folds (B1 and B2) are recognized and the regional folds, a N/S trending anticlinorium to the east and synclinorium to the west, are interpreted as second generation structures (B2). First generation folds (B1) are refolded by B2 on the limbs of the large B2 structures and are commonly recumbent. In the hinges of the regional B2 folds, B1 axial planes are steeply dipping and the folds instead of being refolded by B2, are more tightly appressed than elsewhere. A model is described to explain these observations.     

宜昌奥陶纪的古环境演变

<正> 宜昌黄花场的奥陶系剖面,1972年以来逐渐作为我国研究奥陶系的标准剖面。宜昌王家湾的奥陶系—志留系界线剖面在国际上也被认为是界线对比的标准。本文仅就古环境方面的研究进行初步探讨,研究的标本(编号ACC)采用穆恩之等1972年测制的剖面。     

滇西保山地区的石炭系

<正> 滇西保山地区石炭系研究较早。Cowper Reed(1927)描述施甸早石炭世的珊瑚Siphonophyllia of. caninoides, Palaeosmilia fraterna等。王鸿祯(1945)讨论过本区石炭系的划分与对比,在施甸由旺西山及保山二十五里铺找到珊瑚 Pseudouralinia keyserlingophylloides, Siphonophyllia huangi, Kueichouphyllum sinense, Lithostrotion irregulare等,肯定了杜内阶上部及维宪阶地层。并认为,在保山瓦房街位于维宪阶之上的一套厚170米杂色     

Paleosols and the forest border in Keewatin,N.W.T.

The morphology of paleosols and radiocarbon-dated charcoal from buried surface horizons of soils provide evidence to suggest that between periods of northward forest encroachment tundra climate has dominated areas at least 50 km south of the present forest/tundra border in southwest Keewatin. The present forest/tundra border climate is nearly as severe as any climate that has prevailed in the area since deglaciation.     

Resolution of foraminiferal biotopes in Broken Bay,N.S.W.

A recent benthonic foraminiferal population consisting of 144 species from an interacting marine‐estuarine environment has been analysed by Q‐mode cluster analysis to reveal biotopes. Simplification of the total populations, both in terms of abundance and occurrence, discloses that the more significant subpopulation is composed of the widely‐occurring species. Subpopulations based on rarely occurring but locally abundant species do not define meaningful biotopes.     

Petrology of the Nandewar Volcano,N.S.W., Australia

The Nandewar Mountains, N.S.W., Australia, are the remains of a Miocene continental alkaline volcano whose products range from olivine basalts to comendites and alkali rhyolites. Intermediate hawaiites, mugearites and benmoreites predominate in the shield, in which olivine basalts are rare, and the trachytic rocks form many intrusions into the shield. The Nandewar alkaline series shows extreme fractionation of a relatively differentiated alkali olivine basalt magma, saturated with silica, to yield extremely oversaturated peralkaline comendites and peraluminous alkali rhyolites. The nature of the ferromagnesian phases forming was controlled by low oxygen fugacities. Throughout the series clinopyroxenes range from diopsidic augite, through sodic ferrohedenbergites to hedenbergite-acmite solid solutions. Riebeckite-arfvedsonite solid solutions appear in the trachytes and comendites, and aenigmatite appears in some of the peralkaline rocks. The feldspars in the series fractionate from calcic labradorite through potash oligoclase and calcic anothoclase towards the minimum melting alkali feldspar composition, Ab₆₅Or₃₅. The compositions of the alkali rhyolites approach the minimum in the system SiO₂-KAlSi₃O₈-NaAlSi₃O₈. All the mineralogical and chemical evidence points to the development of the Nandewar series by the processes of extreme crystallization differentiation of an alkali olivine basalt parent magma. No significant contamination occurred, xenoliths and xenocrysts are absent, and volatile transfer and metasomatism played a minor role.     

Geomorphology and tectonics of the Dorrigo Plateau,N.S.W.

The Dorrigo Plateau is covered by basalt, which is a remnant of the 18 Ma old Ebor Volcano. The centre of this volcano is an intrusion in the Bellinger Valley. The volcano was erupted on a palaeoplain of moderate relief. Subsequent uplift and tilting led to erosion of the Nambucca Beds, together with much of the volcano, and creation of a major escarpment, part of the Great Escarpment of eastern Australia. In this area the Great Escarpment is younger than 18 Ma.     

Some Feldspars, Nephelines and Analcimes from the Square Top Intrusion, Nundle, N.S.W.

The Square Top intrusion, near Nundle, New South Wales, revealsin its mineralogy and chemistry the transition of analcime-olivinetheralite to analcime tinguaite. Chemical, X-ray, and opticaldata are presented on 2 plagioclases, 9 alkali feldspars, 2nephelines and 3 analcimes, from various members of the differentiationsequence. With differentiation, plagio-clase becomes enrichedin Ab and, to a lesser extent, in Or. The coexisting alkalifeldspars initially reveal enrichment in Ab and trend from sanidineto lime anorthoclase; subsequently in the tinguaites, the sanidinesbecome enriched in Or. Nephelines in the lower theralites havehighly sodic compositions and become slightly enriched in Kin the later differentiates. Replacement of Si by NaAl in theanalcimes decreases with progressive differentiation. The rapidcooling of this relatively small intrusion assisted fractionalcrystallization, and resulted in the preservation of disorderedplagioclase and alkali feldspars. The Square Top feldspar crystallizationtrends are compared with trends presented by Tuttle and Bowen(1958). The location of the feldspar boundary curve in the Ab–An–Orsystem and some general relationships in the undersaturatedportion of the Ne–Ks–Qz system, including the heteromorphicfelsic assemblages developed from the lowest temperature liquids,are also discussed.     

Grain-size spectra maps of beaches in W. Peloponnese, Greece

Grain-size spectra maps of sands from beaches of the western Peloponnese are related to statistical parameters and can be used to infer characteristics of the sedimentation process involved which were unresolved by previous statistical analysis. On the basis of similarities in spectral patterns, the studied beaches fall into four groups: A, B, C, and D. The periodicity observed on the sinuous pattern of the spectra map of groups A and B is interpreted as indicating edge-wave activity. Regarding group D, the gradual W—E increase of particle size along the coast suggests a W—E increase of wave energy, which is also reflected by the inclined trend of the spectra map. Lack of periodicity on the contour pattern of group C probably reflects intensive sample-to-sample sorting variation.