摘要:

SUMMARYThe feasibility is discussed of using anisotropy of magnetic susceptibility to find preferred directions of grain orientation and current directions in sediments, and it is concluded that it should be possible to find these directions in silts and sands containing between 0.01 and 1% of magnetite.Some examples are given of the use of the method under controlled conditions, and it is shown to give the same result as optical grain orientation determination in one example and to predict the same current direction as macroscopic indications in two others. Some of the limitations of the method are suggested by examples in which the results would have been misleading if accepted unconditionally.

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1965.tb01550.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYSize, flatness, and orientation of both maximum projection plane and longest axis were measured on 298 particles larger than 32 mm on two gravel bars in a modern stream in southeastern Indiana. Maximum projection planes dip into the current and long axes are transverse to it. Size and flatness have little effect on orientation.

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1965.tb01551.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYSpeleothems of Great Onyx Cave, Kentucky, are composed of calcite, aragonite, and gypsum. Calcite is present in all carbonate samples, and where aragonite is also present, the speleothem core is always of calcite, overlain by a progression of alter‐ nating shells of aragonite and calcite, calcite being the outermost carbonate shell. In some specimens, gypsum encrusts these other two phases but is never itself enclosed by a carbonate, thus demonstrating that carbonate deposition was complete in these specimens before sulfate deposition began.Cave temperature is constant at 12.5°C. The pH‐values of standing and dripping water ranged from 7.5 to 8.7, with the value of 8.7 being recorded where precipitation and crystallization of calcite was taking place. At a pH of 8.7, some authors consider that calcium carbonate should normally crystallize as aragonite, but in the cave studied, pH seems to have little effect and temperature may be the controlling factor.Strontium is measurable in most of the aragonite‐bearing samples and not in the calcite ones. But two calcite stalactites and separated calcitic portions of mixed aragonite‐calcite stalactites contain considerable quantities of strontium. Although the affinity of strontium for the aragonite lattice is demonstrated, it is probable that in these cave deposits, the strontium did not have a primary influence on the poly‐ morph which cr

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1965.tb01552.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYUpper Triassic Lockatong argillite (lacustrine facies) and reddish‐brown Brunswick mudstone (mudflat facies) contain numerous pseudomorphs after glauberite. Those in the Brunswick Formation are large calcite casts of complete crystals both isolated and in bunches in beds a few inches thick, or are slender skeletal crystal casts forming open‐work rosettes in massive mudstone. Those in analcime‐rich dolomitic Lockatong argillite are smaller, more slender, skeletal crystal‐casts filled with dolomite and analcime; most of them are scattered through the rock but locally arranged in vague geometric patterns; less commonly they form conspicuous rosettes and downward‐ diverging conical sprays.Many glauberite crystals (and rarely halite in the Brunswick mudstone) grew in soft mud during Late Triassic time, thus emphasizing dryness and the role of saline water in the later history of the closed carbonate‐sulphate Lockatong lake. Early extraction of calcium and magnesium carbonates and later of sodium and silica during each chemical cycle left the lake enriched in calcium, sodium, and sulphate. These crystallized as glauberite and possibly anhydrite in lake‐bottom mud and in surface mudcracks during the waning of a chemical cycle.Crystals of the soluble salts in the Lockatong mud were then replaced by dolomite and analcime from solutions released during dewateri

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1965.tb01553.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYIn principle, sedimentary folding in Early Ordovician limestones in Sweden corres‐ ponds to the arching of a marble plaque on the wall of the “H6tel de Ville” of Cham‐ bery. This folding is due to dilatation within an unyielding frame by the swelling of a certai

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1965.tb01554.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Sedimentary Manganese Ores. I. M. Varentsov.

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1965.tb01555.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY