Abstract
The Yorkshire Lower Lias consists essentially of fine-grained sediments, in the clay to fine silt size range. The occurrence of several types of shellbed, siliciclastic layers and concentretionary horizons makes it possible to distinguish five stratigraphically distinct facies, which can be interpreted in terms of specific depositional environments. To investigate the presence of cyclicity, spectral analysis has been applied to three geochemical time series all covering the bottom 10 m (=20 couplets) of the Banded Shales unit, and to a gamma-ray log of the adjacent Felixkirk Borehole. Within the dating limitations of the ammonite zonation scheme it seems possible to distinguish the precession, obliquity and eccentricity cycles of the Earth's orbit. Based on this evidence it is suggested that orbitally forced climatic changes influenced the depositional system at two levels: 1) short-term variations expressed on a couplet scale, affecting the storm frequency and perhaps magnitude; and 2) longer term variations affecting weather and clay production in the source area. -from Authors
| Original language | English (US) |
|---|---|
| Pages (from-to) | 345-366 |
| Number of pages | 22 |
| Journal | Orbital forcing and cyclic sequences |
| State | Published - Jan 1 1994 |
| Externally published | Yes |