10 | Halliburton Landmark
The Ups and Downs of Short-term
Cretaceous Sea-level Change: An
Attempt to Quantify the Magnitude of
Ancient Eustatic Changes
Exploration Insights | 11
WHAT’S NEW IN
®
NEFTEX INSIGHTS
by: David C. Ray, Mike Simmons, Frans S.P. van Buchem,
Graham Baines, Andrew Davies, Benjamin Gréselle, and
Christopher Robson
GUYANA-SURINAME KEEPS ON
GIVING
Recent Cenozoic discoveries in adjacent blocks such
as Jethro/Joe (Orinduik Block), and the Cretaceous
discovery at Maka Central-1 (Block 58, Suriname),
indicate that the potential for exploration success
exists outside the prolific Stabroek Block.
Learn more...
GLOBAL SOURCE ROCK AND
RESERVOIR INSIGHTS IN THE
DYNAMIC PALEOGENE WORLD
We have created three, new, fully-integrated
global Neftex ® Palinspastic Digital Elevation
Models (PDEMs), and Neftex Palinspastic Gross
Depositional Environment (PGDE) maps, for the
Paleogene.
Learn more...
UPDATED ISOCHRON POINT DATA IN
PLATE MODEL
The isochron points available as supporting data within
the plate model have been significantly updated. They
now include the isochron points made available by The
Global Seafloor Fabric and Magnetic Lineation Data Base
Project.
Learn more...
Stratigraphic architectural response to sea-level fluctuations in Barremian strata at La Montagnette in the Vercors region, France. The
prominent cliff is dominated by highstand progradation. Source: Mike Simmons (Halliburton)
WHY IS THE MAGNITUDE OF SEA-
LEVEL CHANGE IMPORTANT?
Isolating the eustatic signal from the sedimentary
record remains challenging, yet much progress
is being made towards understanding the timing,
magnitude, and rate of Phanerozoic eustasy
on both long-term (10 7 –10 8 yrs) and short-
term (10 5 –10 6 yrs) scales. Eustasy contributes
to the sequence stratigraphic organization of
sedimentary successions and is a fundamental
consideration in the majority of Neftex ® products,
including our gross depositional environment
maps, chronostratigraphic charts, and wells.
An ability to determine the eustatic signal is,
therefore, important for our understanding of the
stratigraphic record, helping us to understand the
often-incomplete nature of the geological record.
The ability to quantify the magnitude of the
pervasive short-term sea-level signal is of
considerable importance for hydrocarbon
exploration because it is used to predict reservoir-
scale facies variability. For example, intervals of
significant (>40 m) short-term sea-level variation
are likely to be evident within the stratigraphic
record, being characterized by marked facies
variability and repeated episodes of non-
deposition and erosion. In contrast, intervals
of slight (<10 m) sea-level variations are likely
to be reflective of local drivers of sea-level
change; and where eustatic processes dominate
sedimentation, facies variability will be subdued.
Consequently, variations in the magnitude of
short-term sea-level change should impart an
identifiable and predictable character to the
stratigraphic record.
As short-term eustasy is principally the result
of climatic processes that have characteristic
upper magnitude limits (Figure 1), the magnitude
of sea-level change can be used to identify the
dominant process (i.e. glacio-eustasy, thermo-
eustasy, or aquifer-eustasy). For example,