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DYNAMIC STRATIGRAPHY WORKGROUP |
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Tidal bar architecture in the Eocene Baronia Sandstone, Ager Basin, Spain
People:
Research Question:
What is architecture of tidal bars described previously in Piggy-Back Ager Basin in southern Pyrenees?
This project is following previous studies on tidal deposits with the aim to better understand the architecture of tidal bars. Because of the highly variable current changes the architecture and heterogeneities of shallow water tidal deposits are more complicated than fluvial or wave dominated deposits. Despite multiple studies on modern and recent tidal deposits there are not many studies on ancient tidal deposits and even less that focus on tidal bar deposits.
Summary of work: Our observations on lower Eocene deposits of the lower Baronia sandstone, in Ager Basin, indicate that the tidal deposits represent tidal dunes rather than tidal bars. The interpretation is based on the detailed architecture of the tidal deposits. The tidal bars are thought to build mainly through the lateral migration relative to the dominant paleoflow and therefore the preserved accretion surfaces will be oriented at high angle relative to the paleoflow. The tidal dunes have a dominant forward migration component (similar to deltas!) and therefore the accretion surfaces will be oriented at low angle to the paleoflow. The difference between tidal dunes and bars is important for hydrocarbons reservoir characterization because the sand-bodies will have a different orientation and the internal heterogeneities (flow barriers) will be different. Based on the sedimentology and ichnology of the Baronia deposits we also reinterpret the paleo-geography of the Ager Basin during Lower Baronia as a tidal dominated strait or seaway with large dunes migrating under dominant eastward or westward oriented currents. This interpretation is different from the previous interpretation that Ager Basin was a gulf that received a large river input from the east. |
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Publications and presentations:
Publications
Conference/meeting presentations
Olariu, C., Steel, R.J., Dalrymple, R.W., and Olariu, M.I., 2009, Distinguishing Tidal Bars from Tidal Compound-Dunes in Ancient Deposits Why Bother?, IAS Annual Meeting, Alghero, Italy.
Dalrymple, R.W., Olariu, C., Steel, R.J., Gingras, M., and Rubino, J. L., 2008, Tidal Dunes of the Eocene Baronia Sandstone, Ager Basin, Spain: A Reinterpretation of the Type Area for the “Tidal-Bar” Facies Model, 7th International Conference on Tidal Environments Qingdao, China. |
