Eighth Edition
by Harold L. Levin

Chapter 5 - page 1

The Sedimentary Archives

Introduction

The characteristics of sedimentary rock deposited in an area depend on:

1. Tectonic setting.
2. Physical, chemical, and biological processes in the depositional environment.
3. Method of sediment transport.
4. Rocks in source area from which sediment is derived.
5. Climate (and its effect on weathering).
6. Post-depositional processes of lithification (cementation, compaction).
7. Time.

Tectonic Setting

Tectonics: The forces controlling deformation or structural behavior of a large area of the Earth's crust over a long period of time.

An area may be:

• Tectonically stable - like the midwestern US.
• Subsiding (sinking) - like New Orleans or Mexico City.
• Rising gently - like New England and parts of Canada after glacier retreat.
• Rising actively to produce mountains and plateaus - like parts of Oregon in the Cascade Mountains .

Tectonics influences the grain size and thickness of sedimentary deposits.

Recent uplift of the source area leads to rapid erosion of coarse-grained sediment.

Subsidence in the depositional basin leads to the accumulation of great thicknesses of sediment.

Note thick accumulations of shallow water sediment in the Appalachians.

Principle tectonic elements of a continent

Craton - Stable interior of a continent, undisturbed by mountain-building events since the Precambrian.

• Shields - Large areas of exposed crystalline rocks.
• Platforms - Ancient crystalline rocks are covered by flat-lying or gently warped sedimentary rocks.

The craton and orogenic belts of North America.