Plants, Their Fossilization, and Techniques of Fossil Study

Abstract

If you have ever watched moving water carry sand grains, silt particles, twigs, seeds, leaves, or in flood time large logs and even houses, you have watched what may be a preliminary stage in the formation of fossils. When the stream slows down as it meets a body of standing water, such as a pond, lake, or sea, its load begins to be dropped or to sediment out. The heavier particles are dropped first, closer to shore, and the lighter particles are dropped farther from shore. Changes in the rate of flow of the moving water produce variations in the size and type of particles deposited over any particular area. In this way a delta is built up (Fig. 1-1). A vertical section through the deltaic deposits may reveal layers of varying thickness and constitution, some sandy, some muddy, some with otherwise mixed particles. Fig. 1-2 shows rock strata that were built up in this way.