Final answer:
Stratigraphy is the study of rock layers, focusing on the principles of superposition and stratigraphic superposition, vital for dating methods in geology and archaeology. It includes subfields such as biostratigraphy and lithostratigraphy, and uses observations and techniques like seismic surveys to analyze and date strata.
Step-by-step explanation:
Understanding Stratigraphy
Many dating methods are based on stratigraphy, a branch of geology focusing on the study of rock layers (strata) and layering, which is crucial in understanding geological time. Stratigraphy involves two fundamental principles: the law of superposition and the concept of stratigraphic superposition. The law of superposition dictates that in any undisturbed sequence of strata, the oldest layer is at the bottom, and each successive layer is younger than the one beneath it. When it comes to archaeological stratification, this principle helps to date artifacts based on their relative depths within these layers. This principle also holds for natural forces and human intervention that might disturb these layers.
Stratigraphy is not limited to identifying the order and relative positions of the strata; it also concerns biostratigraphy and lithostratigraphy. Biostratigraphy uses fossils found within the strata to infer the age and depositional environments of sedimentary rocks. For instance, distinct pig species in different strata at Olduvai Gorge allowed paleoanthropologists to establish the stratigraphy and to date the layers relative to each other. Lithostratigraphy analyzes the rock layers themselves.
Geologists conduct stratigraphic studies through techniques like outcrop observations, sediment cores collection, and seismic surveys. These help to understand not only the sequence but also the characteristics and contents of the strata. Objects found within, or cutting through, several strata indicate they are younger than the strata they disturb, essential for understanding stratigraphic relationships and dating.