Abstract
Nannofossils are restricted largely to the Greenhorn and Niobrara cycles, with most study to date concentrated on the Greenhorn cycle assemblages. Paleoecologic studies of the Greenhorn indicate initial invasion of oceanic waters into the basin from the south, with rapid lateral and northward expansion. Assemblage diversities are initially low, but attain open ocean values by peak transgression. Two surface watermasses (northern and southern) are evident at initial oceanic invasion, with a third developing by peak transgression. Rhythmic bedding in the Greenhorn near peak transgression appears related to surface water fertility cycles. Studies in the Niobrara indicate the presence of seven standard nannofossil zones. -from Authors
Original language | English (US) |
---|---|
Pages (from-to) | 521-537 |
Number of pages | 17 |
Journal | Geological Association of Canada Special Paper |
Volume | 39 |
State | Published - 1993 |
All Science Journal Classification (ASJC) codes
- Fuel Technology
- Geology
- Geochemistry and Petrology