Publication Date:
2009-04-01
Description:
Sequence stratigraphy has been applied from reservoir to continental scales, providing a scale-independent model for predicting the spatial arrangement of depositional elements. We examine experimental strata deposited in the Experimental EarthScape facility at St. Anthony Falls Laboratory, focusing on stratigraphic surfaces defined by discordant contact geometries, surfaces analogous to those delineated in the original work on seismic sequence stratigraphy. In this controlled setting, we directly evaluate critical sequence-stratigraphic issues, such as stratigraphic horizon development and time significance, as well as the internal geometry and migration of the bounded strata against the known boundary conditions and depositional history. Four key stratigraphic disconformities defined by marine downlap, marine onlap, fluvial erosion, and fluvial onlap are mapped and vary greatly in their relative degree of time transgression. Marine onlap and downlap contacts closely parallel topographic surfaces (time surfaces) and, prior to burial, approximate the instantaneous offshore topography. These stratal-bounding surfaces are also robust stratigraphic signals of relative base-level fall and rise, respectively. Marine onlap surfaces are of special interest. They tend to be the best preserved discordance, where widespread, allogenic-based onlap surfaces subdivide otherwise amalgamated depositional cycles amidst cryptic stacks of marine foresets; however, local, autogenic-based marine onlap discordances are present throughout the fill. A critical distinguishing feature of allogenic onlap is the greater lateral persistence of the discordance. Surfaces defined by subaerial erosional truncation and fluvial onlap do not have geomorphic equivalence because channel processes continually modify the surface as the stratigraphic horizons are forming. Hence, they are strongly time transgressive. Last, the stacking arrangement of the preserved bounded strata is found to be a good time-averaged representation of the mass-balance history. John M. Martin is presently at ExxonMobil Upstream Research Company, where his research interests are in geomorphology and the details of stratigraphic accumulation from a variety of depositional environments. He earned his Ph.D. from the University of Minnesota, Minneapolis, where much of his work was centered at St. Anthony Falls Laboratory. Chris Paola is a professor in the Department of Geology and Geophysics, University of Minnesota, Minneapolis, and does research at St. Anthony Falls Laboratory. His research interests are in physical sedimentary geology and stratigraphy, especially the dynamics of channelized systems. He received his B.S. degree in environmental geology from Lehigh University, his M.S. degree in applied sedimentology from the University of Reading, and his D.S. degree in marine geology from Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography. Vitor Abreu received his Ph.D. from Rice University and is presently an ExxonMobil stratigraphy coordinator. He is also an adjunct professor at Rice University, teaching sequence stratigraphy and has published several articles and given numerous talks and seminars within industry and academia. He was the recipient of the Jules Braunstein Memorial Award (2002 AAPG Annual Meeting) and is currently an AAPG distinguished instructor. Jack E. Neal received his B.S. degree from the University of Tulsa and his Ph.D. from Rice University. His interests are seismic and sequence stratigraphy, structure-stratigraphic interaction, paleoclimate, and hydrocarbon systems. He has published on northwestern Europe sequence stratigraphy, graphic correlation, and lacustrine sequence stratigraphy. He has worked globally in research, exploration, development, and production assignments with Exxon and ExxonMobil since 1994. Ben Sheets is an assistant professor of marine geology and geophysics in the School of Oceanography at the University of Washington, Seattle. He earned his B.A. degree from Carleton College and his Ph.D. from the University of Minnesota, Minneapolis. His research involves processes, geomorphology, and stratigraphy in a variety of coastal and submarine sedimentary systems.
Print ISSN:
0149-1423
Electronic ISSN:
1943-2674
Topics:
Geosciences
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