Deep sea sedimentation

Our plain-English summary of Deep sea sedimentation, by P.E. Biscaye (Environmental Health Perspectives, 1974).

The study

• Author: P.E. Biscaye
• Journal: Environmental Health Perspectives
• Published: 1974;9:177-8
• Read it: PubMed · Publisher · Free full text

Abstract

An important problem in the study of microparticles in the marine environment, suspended in the water column or deposited as sediment on the ocean bottom, is the determination of provenance of the microparticles-where did they come from and by what processes were they transported to the sampling location? Two techniques of possible interest to those concerned with tracing the origins and dispersion paths of asbestos particles are described. One utilizes variations in the naturally occurring rubidium-strontium isotope system and is used to characterize a bulk sample, i.e., a large number of particles. The other utilizes scanning electron microscopy to observe variations in surface texture of individual grains which, in the case of quartz particles in the natural environment, can be related to the transport processes to which they have been subjected.

In plain English

This article described two techniques the author used to trace where particles in sediments, sea water and dust came from. It reported no asbestos measurements or health data. The author presented both as of possible interest for tracing asbestos particles, saying the first could, with enough sample material, characterize asbestos sources from terrains of different geologic ages. It used natural rubidium-strontium isotopes to give a bulk sample an "apparent age" reflecting its continental source. Apparent ages at about 150 Atlantic points ranged from under 300 million years in the South Atlantic to over 2000 million years near the Canadian Shield. Dusts sampled across the Atlantic and on Barbados gave about 500 to 750 million years, similar to eastern Equatorial Atlantic sediments at that latitude, east of the Mid-Atlantic Ridge. West of the Ridge at that latitude, sediments were significantly lower than both. The author concluded wind-borne African dust appeared to be the major influence on deep-sea sediments east of the Ridge there. A second technique, scanning electron microscopy of quartz grain surfaces, indicated a large portion of Argentine Basin sediment came from Antarctica, not South America.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: descriptive methods article (brief account by one author of two geochemical techniques for tracing particle origins, with example applications)
• Who was studied: deep-sea sediment samples at about 150 data points in the Atlantic Ocean, dust samples collected from ships and on Barbados, and sediment from the Argentine Basin east of southern South America; no people were studied
• Exposure: no asbestos or human exposure was studied; the author presented both techniques as of possible interest for tracing asbestos particles, and said the rubidium-strontium technique could be used to characterize sources of asbestos
• Main results:
  • Across the Atlantic, sediment apparent ages ranged from less than 300 million years in the South Atlantic to more than 2000 million years next to the Canadian Shield
  • Dusts sampled from ships across the entire Atlantic and on Barbados had apparent ages of about 500 to 750 million years, similar to deep-sea sediments at that latitude in the eastern Equatorial Atlantic, east of the Mid-Atlantic Ridge
  • In this Equatorial Atlantic comparison, sediments west of the Mid-Atlantic Ridge had significantly lower apparent ages than both the dusts and the sediments east of the Ridge
  • Quartz grain surface textures indicated that a large portion of Argentine Basin sediment came from Antarctica rather than the adjacent South American continent
• The authors' conclusion: For the Equatorial Atlantic, the author concluded that wind-borne African dusts appear to be the major influence on deep-sea sediments east of the Mid-Atlantic Ridge, while west of the Ridge they are diluted by sediment from other sources. The author also suggested that the isotope technique could be used to characterize sources of asbestos.

Topics

Medical terms in this study, explained in our Lexicon: Scanning Electron Microscopy (SEM).

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