Strata and Maps
Maps
- Various efforts in geognosy tradition, capped by Cuvier and Brongniart (1808, 1811)
- Smith’s map of Britain
- Essentially completed around 1803, published 1815
- Unique shading
- Formation names: locality + lithology
- Not readily comparable to parallel efforts elsewhere
- Recognition of characteristic fossils of specific formations
- Webster’s map and sections of the Isle of Wright Basin (1814)
- Uppermost Secondary (Chalk) and lowest Tertiary strata
- Both deformed (folded)
- Attempted to match Tertiary beds to Paris Basin using lithology
Formation Issues
- Shift from gebrige to formation
- Gebrige: lithology/mineralogy, dip, position, altitude
- Formation: lithology, position in sequence
- Correlation
- Criteria tried: rock type, structural position, dip, altitude, fossils
- By 1820, rock type still predominate one
- Fossil info noted but not yet primary criteria
- International correlations emerge by early 1820s
Ideas on Geology around 1820
- Examples
- London: London Basin
- Milan-Turin: Po Valley
- Naples: Volcanic fields
- Edinburgh: Scottish Lowlands and Southern Uplands
- Zurich: High Alps and Tertiary lowland (Swiss Plain)
- General ideas
- Tertiary
- Isolated basins
- Identify and map formations; include fossils
- Attempt to correlate basins
- Work out relation of sediments to adjacent uplands
- Secondary
- Section more regular across Europe (i.e., Coal Measures to Chalk)
- Need to add fossil data and map new areas (Scotland, Switzerland, etc.)
- Primary and Volcanics
- Work on relationships between these and stratified units (ex: dikes)
- Recall problems of origin of basalt and magmas
- Examine dip and altitude of crystalline rocks
- Sea level fall (classic model) versus uplift (new idea)
- Need to figure this out
- Tertiary sections high in the Alps (?)
- Correlation
- By this time, rock type is the most useful
- Other geognost criteria fail
- Need to test fossils as tools
- Tertiary