Figure 3. Photograph of excavated exposure in a gravel pit in a delta in Whitefield, Maine. The person in the lower right hand corner of the photo is standing adjacent to the foreset beds of the delta. The foreset beds form as sediment is brought to a lake or the ocean by streams and is deposited at the delta and cascades down the delta's front slope. As the delta builds outward, stream sediments called topset beds are deposited on top of the front slope foresets. In the photo from the top of the face downward, about one-quarter of the exposure is comprised of horizontal layers of gravelly sand. These horizontal layers are the topset bed deposits brought by streams to the ocean and deposited over the foreset beds. The boundary (white line) between the horizontal beds and the dipping beds is called the topset / foreset contact. It represents the approximate position of the surface of the body of water into which the streams entered, resulting in the creation of the delta.
Last updated on October 6, 2005