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Vineyards, Rocks, and SoilsThe Wine Lover's Guide to Geology$
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Alex Maltman

Print publication date: 2018

Print ISBN-13: 9780190863289

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780190863289.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 25 September 2021

Sediments and Sedimentary Rocks

Sediments and Sedimentary Rocks

5 (p.69) Sediments and Sedimentary Rocks
Vineyards, Rocks, and Soils

Alex Maltman

Oxford University Press

We are on more familiar ground in this chapter, looking at processes and materials found in the world all around us. Even the names of sedimentary rocks are well known–sandstone, shale, limestone, and so on. Clearly, these materials are highly relevant to vineyard geology because more than three-quarters of the land surface is sedimentary in origin: most of the world’s vineyard areas are underlain by sedimentary rocks. Sediment is the detritus produced from the weathering of already existing rocks. (I explore the process in Chapter 9.) Usually, wind, ice, or water soon moves the debris away, eventually to be deposited and then buried beneath further sediment and with time hardened into sedimentary rock. Weathering can also dissolve material, later to be precipitated. And, needless to say, all the sediment in question here is of geological origin; it has nothing to do with the organic sediment that is thrown, say, in a bottle of vintage port! Wind and flowing water may be able to pick up sediment and move it, depending on the size of the fragments. Faster-moving currents can carry bigger particles: it’s to do with energy, as discussed in the context of rivers in Chapter 8 (see Figure 8.8). The result is sediment sorting. We can easily see the results on a beach–a sandy spot here, a pebbly patch there–because the tides and shore currents have moved the sediment around and sorted it. Thus, most detrital sediments have a characteristic grain size, and we use this to classify the material. The terms for the different sizes are pretty much in line with everyday language: sand, silt, clay, and so on (Figure 5.1). Clay is the finest sediment. It’s composed mainly of the tiny clay minerals that we met in Chapter 3 and has the smooth, slippery feel and handling properties we’re all familiar with; the individual constituent particles are far too fine to see, even with a powerful hand lens. Imagine: if we scaled up a grain of sand to the size of a wine cask, then an individual clay flake would be smaller than a coin.

Keywords:   Urgonian, abrasion, boulder bed, calcium, diatom, fissility, ironstone, kieselguhr, lithification, magnesium

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