Abstract:
Sequence stratigraphy is a modern method
of stratigraphic analysis, whereby stratal stacking patterns and
facies relationships of sedimentary rocks are studied within a time
framework. Sequence stratigraphy is now routinely employed in both
academic and industry research, to understand local to global changes
in the geological record, to improve the predictability of petroleum,
coal and mineral resources exploration, and to optimize the
development of petroleum-producing reservoirs.
In spite of its popularity, the sequence stratigraphic method tends to
be confusing and hence difficult to apply because of the proliferation
of an unnecessarily complicated terminology, with several synonymous
terms for the same concept, or similar terms for different concepts.
In addition to this, the existence of several different approaches to
sequence stratigraphy complicates further its applicability. This
paper takes a balanced approach to explaining what is the relationship
between all existing approaches, what are the reasons for having this
diversity of opinions, and what is the logical way that would help one
select the optimum approach for each case study. Ultimately, all
current approaches are correct in the context under which they were
proposed. The proponents of each model have often used case studies
from different sedimentary basins to support their methodology, which
explains the difference of opinions that is observed today. The
applicability of the sequence stratigraphic model varies with the data
set that is available for analysis (e.g., seismic data versus well
logs or outcrop), tectonic setting, depositional setting, and the
scale of observation. Taking the right decision regarding the method
that provides the optimum approach under specific circumstances
requires an emphasis on depositional processes rather than terminology
or other model-dependent assumptions. This promotes flexibility in the
application of sequence stratigraphy, and guides the practitioner
through a process-based, model-independent approach.
The lack of formal inclusion of sequence stratigraphy in the current
international stratigraphic codes may be attributed largely to trivial
differences in terminology and the style of conceptual packaging of
the rock record into sequences and systems tracts. The choice of how
we name the packages of strata between specific sequence stratigraphic
surfaces varies with the model, which is why the systems tract
nomenclature becomes less important than the correct identification of
the stratal stacking pattern which defines that particular package of
strata. Even the selection of what surface (or set of surfaces) should
serve as the ‘sequence boundary’ becomes subjective and trivial to
some extent, as the correct interpretation of all sequence
stratigraphic surfaces and of the origin of strata that separate them
is far more important for the success of the sequence stratigraphic
method. Irrespective of the model of choice, the ‘pulse’ of sequence
stratigraphy is fundamentally represented by shoreline shifts, whose
type and timing control the formation of all genetic packages of
strata (systems tracts) and bounding surfaces. Beyond nomenclatural
preferences, each stage of shoreline shift (normal regression, forced
regression, transgression) corresponds to the formation of a systems
tract with unique characteristics in terms of stratal architecture,
sediment dispersal patters and distribution of depositional elements
across a sedimentary basin. These fundamental principles are common
among all models, and allow for a unified sequence stratigraphic
approach. Finding the common ground between the various ‘schools’ is
the key for making real progress towards standardizing the concepts of
sequence stratigraphy (Catuneanu, 2006).
Reference:
Catuneanu, O. (2006) Principles of Sequence Stratigraphy. First
Edition, Elsevier, Amsterdam, 375 pp.
Brief Biography of the Speaker:
Octavian Catuneanu is Professor in the Department of Earth and
Atmospheric Sciences at the University of Alberta, with Ph.D. degrees
from the University of Toronto (1996) and the University of Bucharest
(1992). He is the recipient of several distinctions in the field of
Geology, including best paper awards from the Geological Society of
America (2002) and the Romanian Academy (1994). Octavian Catuneanu has
served as the Chair of the North American Commission on Stratigraphic
Nomenclature (2005-2006), the Chair of the Canadian Sedimentology
Research Group (a division of the Geological Association of Canada;
2004-2007), and he is the current Chair of the International Working
Group on Sequence Stratigraphy (working towards the standardization of
sequence stratigraphy in the International Stratigraphic Guide and in
the North American Stratigraphic Code). He is the Editor-in-Chief of
the Journal of Marine and Petroleum Geology, and also serves on the
editorial board of the Journal of African Earth Sciences and as an
Associate Editor of the Bulletin of Canadian Petroleum Geology. He is
the author of Elsevier’s textbook titled “Principles of Sequence
Stratigraphy” (Elsevier’s best seller in Earth Sciences, and recipient
of a CHOICE Award for one of the best reference titles), co-editor or
senior editor of several books and special issues, and author of
numerous publications in the fields of sedimentology, stratigraphy and
basin analysis. He is currently involved in several international
research programs and as an instructor of sequence stratigraphy and
basin analysis workshops for conferences and companies worldwide. |
