Frequency Distribution of Thickness of Sediments Bounded by Cenozoic Biostratigraphic Events in Wells Drilled Offshore Norway and along the Northwestern Atlantic Margin |
| |
Authors: | Frits Agterberg Felix Gradstein Gang Liu |
| |
Institution: | (1) Geological Survey of Canada, 601 Booth Street, Ottawa, ON, Canada, K1A0E8;(2) University of Ottawa, Ottawa, ON, Canada, K1N6N5;(3) Geological Museum, University of Oslo, PO Box 1172, Blindern, Oslo, N-0318, Norway;(4) State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074, China |
| |
Abstract: | Sampling for microfossils in exploratory wells in basins with hydrocarbon potential is subject to considerable uncertainty,
mainly because the samples usually are small and subject to caving. Biostratigraphic events defined on fossil taxa include
their last occurrences of which the depths along the wells generally can be measured with precision. The RASC method for ranking
and scaling of stratigraphic events produces an average basin-wide optimum sequence and zonation that can be used for correlation
of strata between wells. In this optimum sequence the fossil events are ordered according to their occurrences in geological
time. Depth differences between successive events in the optimum sequence satisfy a frequency distribution that is of interest
for potentially increasing stratigraphic resolution. In this article the depth difference frequency distribution is modeled
for three large Cenozoic microfossil data sets consisting of 30 wells in the North Sea Basin, 27 wells on the Labrador Shelf
and Grand Banks, and 11 wells in the western Barents Sea. The shapes of the three frequency distributions satisfy bilateral
gamma distributions with similar parameters. These distributions are fitted by the construction of straightlines on normal
Q–Q plots of square root transformed average-corrected depth differences. The gamma distribution model is approximately satisfied
except for small negative and positive depth differences, which have anomalous frequencies because of the discrete sampling
method used in exploratory well-drilling to collect microfossils. It implies not only comparable average stratigraphic order
of events, but also comparable average sedimentation rates in the three Cenozoic basins selected for study. |
| |
Keywords: | Sediment thickness biostratigraphic events exploratory wells bilateral gamma distribution normal Q– Q plots North Sea Basin Northwestern Atlantic Margin |
本文献已被 SpringerLink 等数据库收录! |
|