The Rise of Stratigraphic Geology

New concepts, techniques

• Structural
  • Strike and dip
  • Folds, faults
  • Basin, dome
  • Uplift
  • Marker beds to illustrate structure
• Stratigraphic
  • Formations (replace gebriges) based on lithology
  • Unconformities
  • Incorporate fossils in work
  • Correlation between regions, basins or countries
  • Development of fossil correlation (1830s)
• Display and tools
  • Geological maps
  • Structural cross sections
  • Stratigraphic sections
• Influences are varied
  • Geognosy/Werner, Hutton, Cuvier, Smith, Webster, etc.

System: Changing concepts

• Original idea was a collection of lithologic units bounded by unconformities (see next class as well)
• Murchinson: Discrete and coherent fauna in each system
  • Fossils in Silurian used to correlate across Europe
• Sedgwick: Each system has a consistent structural trend
  • Fossils not abundant in Cambrian
• Devonian
• In part, identified by “transitional faunas” between the Silurian and Coal Measures (Carboniferous)

Correlation

• Significant shift of criteria during all this!
• Lithology was the dominant criteria into the 1830s
  • Recall initial correlations by Buckland (1821), Connybeare and Phillips (1822) and De la Berche (1824)
  • Used by Murchinson and Sedgwick in early work (1830s)
  • Led to the anomaly of the Devonian
• Shift to fossils in the late 1830s-40s
  • Resolved Devonian problem (c. 1839)
  • Used by Murchinson to correlate Silurian (1840s)
  • Used to identify the Permian atop the Coal Measures