Facies Relationships and Sea-Level Change 95 3. Are all of the conglomerates the same age? PART...
Facies Relationships and Sea-Level Change 95 3. Are all of the conglomerates the same age? PART A Correlation of Siliciclastic Rocks The first part of the exercise utilizes the Devonian rocks in New York and Pennsylvania. These rocks formed the basis for the acceptance of the facies con- cept in North America. Fifteen somewhat generalized stratigraphic sections, which were measured through the Devonian rocks at localities approximately 32 km X4. What trend is visible in the sandstone beds as apart, are plotted as logs in figure 7.5. Section 1 is toward the west and section 15 is toward the east in they are traced from east to west? a traverse that lies generally along the New York- Pennsylvania border. Symbols of the lithology are those used in previous exercises. Total thickness of the preserved sections are shown to scale. Various time lines, which have been identi- fied and correlated by the use of fossils, are shown by a series of dots through each column and are marked by small letters. The various time horizons or levels of contemporaneous deposition are shown by the same letters. For example, all the rocks immediately below the dotted line marked "a" in each of the 15 sections were deposited contemporaneously 5. Why do shale beds thin as traced from west to east? 1. Construct a restored section for these Devonian rocks (figure 7.5) similar to the example of Cam- brian rocks in figure 7.4. Detach both pages of fig- ure 7.5 (left and right). Placing them side by side the long way, tape the two pages together and With lines and symbols, interconnect various lithologic units and show the facies rela- tionships of the relatively coarse-grained rocks in the east to the fine-grained rocks in the west. 6. What happens to the sandstone that occurs near 2. Does Walther's law apply to these rocks? Are the base of sections 12, 13, 14, and 15? there exceptions?