Small Fossils with Big Applications—The BP Gulf of Mexico Time Scale—A Step Change in Time Resolution
Boulder, Colo., USA: Geologic time scales are critical to understanding the
timing, duration, and connection of geologic events. They are not static,
and can be improved with research, integration, and refinements realized
from biostratigraphic repetitive analysis. Over the past century they have
proven important tools in petroleum exploration and studies of climatic and
geologic events. Still, many geologists may not know the importance of
microfossils to the construction of time scales and biostratigraphy.
Biostratigraphy was first applied by the petroleum industry nearly a
century ago in the U.S. Gulf of Mexico (GoM) to help understand the geology
of this structurally and stratigraphically complex basin. Nevertheless,
only a few industrial time scales have been published for this region. BP
conducted a multi-decade microfossil research program (circ. 2000) to
produce an integrated planktonic foraminifera and calcareous nannofossil
deep-water GoM time scale. This integrated framework was constructed from
the heritage time scales of BP (Amoco, Arco) and the analyses of hundreds
of GoM wells over several decades.
Today, the culmination of this research is the BP Gulf of Mexico Neogene
Astronomically-Tuned Time Scale (BP GNATTS) that spans the past 25 million
year record from the Late Oligocene (25.05 million years ago) to recent
time. This time scale was primarily calibrated utilizing an orbitally tuned
composite section from Ocean Drilling Program Leg 154 on Ceará Rise and
provides a stratigraphic resolution (number of events per unit of geologic
time) of 144 thousand years. This is approximately double that of published
GoM time scales and a fivefold increase over the highest resolution global
calcareous microfossil timescales.
The resolution of this time scale has provided a valuable aid in seismic
correlations between GoM mini-basins. When applied and integrated with
geological and geophysical data it has helped reveal subsurface details
through detection of unconformities (missing time), sediment redeposition,
slumps, faults, and sand to sand correlation.
The BP GNATTS has been successfully tested outside of the GoM in the
Mediterranean Sea, and with a resolution comparable to eccentricity (~120
thousand years), it lends itself as a possible tool for better calibration
of global records of sea level and paleoclimatic events. One of the most
compelling results of this work is best illuminated in the paper’s final
sentence. “Results presented here lend conviction to the promise that
microfossil biostratigraphy is far from the end of its constructive growth,
rather it is a discipline with great current utility and with a realistic
expectation for developing new and exciting applications.”
FEATURED ARTICLE
BP Gulf of Mexico Neogene Astronomically-Tuned Time Scale (BP GNATTS)
Authors: J.A. Bergen, S. Truax III, E. de Kaenel, S. Blair, E. Browning, J.
Lundquist, T. Boesiger, M. Bolivar, K. Clark. Contact author: Emily
Browing, Emily.Browning@bp.com. Paper:
https://pubs.geoscienceworld.org/gsa/gsabulletin/article/570010/bp-gulf-of-mexico-neogene-astronomically-tuned
.
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