摘要:

SUMMARYThe origin of many sedimentation units deposited in granular cohesionless materials can be rationally explained by utilizing the concept of theprofile of equilibrium.This basic concept can be formally expressed in terms of the variables, or groups of variables, that characterize a sediment transport system. A change in one or more variables or a shift in local base level will generally cause a shift in the spatial position of the profile, resulting in either aggradation or degradation. As shown by flume experiments, the rate of shift of the profile is a critical factor in bedding genesis.A relatively large and rapid upward shift of the profile results in the deposition of a tabular or wedge‐shaped unit of cross‐bedding, i.e., a laboratory delta. On the other hand, a gradual upward shift of the profile results in the deposition of a sequence of horizontal bedding that is commonly associated with intercalations of ripple or dune cross‐bedding. For the intermediate case of a moderately rapid shift of the profile, the depositional sequence includes trough units and poorly‐defined tabular units of cross‐bedding with numerous intercalations of horizontal bedding. The concept of the profile of equilibrium therefore provides a rationale for considering the depositional framework for sedimentary structures produced by cur

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01580.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYA study of six gravity cores from an abyssal plain at the western side of the Madeira‐Cape Verde Basin shows that individual turbidites can extend over a distance of at least 35 miles (65 km) in this area of final turbidity current deposition. Cores from the continental rise include relatively thinner turbidites; evidence from one of these indicates some local erosion of the sea floor: this apparently did not exceed 15 cm (as represented in the core

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01581.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYSome results of turbidity‐current theory are applied to analyses of turbidite layers in cores from the route of a large turbidity current of sheet‐flow type. Novel features are that current velocity is estimated from the sediment sizes deposited, and the lateral spreading of the current is considered. An approximate quantitative picture of the current is obtained. It is compared with the turbidity current which caused the Grand Banks cable bre

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01582.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYCalcareous siltstone beds in the sub‐littoral marine sedimentary rocks of the highest Ludlovian (Upper Whitcliffian) in south Radnorshire display symmetrical ripples with wave lengths around 30 cm. These structures are interpreted as having been formed by the deposition of calcareous silt layers in conformity with bottom surfaces previously scoured into a pattern of symmetrical, gently‐rounded, crests and troughs; hence, they are termed scour ripples. There is some evidence of a longitudinal relationship between the scour ripples and the scouring and depositing currents involved in their format

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01583.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe large and extensive transverse and barchane dunes of coastal South West Africa are strongly oriented under the influence of predominantly southerly winds. During periods of strong winds (40–50 miles/h) deposition occurs on the lee slope in three ways: (1) sand is blown over the crest of the dune and falls on the lee slope; (2) rapid deposition near the dune crest results in periodic slumps and slides down the lee slope; (3) eddy currents developed to the lee of the dune pick up sand from the surface downwind from the dune and transport it to the lee slope.The size and strength of the lee eddy is surprising. With winds in the 40–50 miles/h range frequent gusts lift fine sand from the downwind surface to a height of several feet. Less frequently sand is picked up from a low position on the lee slope and redeposited higher on the slope. The addition of material to the lee slope by the eddy is much less volumetrically than the contribution directly over the dune crest from the windward direction; however, with strong winds the removal and transportation of sand from the area downwind of the lee slope back to the lee slope appears to be important in the deflation of this surface. The width of the area influenced by the lee eddy during strong winds is about equal to the height of the dune.Observations in low dunes from 1 to 20 ft. high at Sapelo Island, Ga., U.S.A., confirm the presence of a well developed eddy to the lee of these dunes during strong and moderate winds (20–50 mil

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01584.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYSand dikes that have been found in Recent desert sediments are described, and an explanation of their origin is presented. The Recent dikes are compared with ancient ones of Permian age.

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01585.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYThe communication describes dome‐like masses of sand apparently developed by gully erosion on the upper surfaces of Ordovician sandstones. The similarity of these structures to the minor topography of tidal marshes is noted, and it is suggested that similar processes may be responsibl

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01586.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

SUMMARYA series of samples from the continental shelf off New Jersey reveals a continuous surface layer of fine sand overlying a variety of sediment type. Ripples and shell debris suggest the fine sand is reworked and is in adjustment with the present shelf environment.

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01587.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01588.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Book reviewed in this article:The Identification of Detrital Feldspars—Developments in Sedimentology. 6. L.van der pla

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1966.tb01589.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY