Acknowledgments & References The modeling study is partially funded by the Geological Society of America and American Association of Petroleum Geologist. We thank Husky Energy for the general support of our modeling lab. We also thank TGS/Nopec Geophysical Company, ConocoPhillips, Canadian Department of Natural Resources, Canada-Nova Scotia Offshore Petroleum Board, and Suncor Energy for providing the seismic data used in this study. A special thanks also goes to Schlumberger for providing Petrel, the software tool that we use to interpret the seismic data. Withjack, M. O. and Callaway, S., 2000. Active normal faulting beneath a salt layer: An experimental study of deformation patterns in the cover sequence. AAPG Bulletin, v. 84, no. , p. 627-651. Eisenstadt, G. and Sims, D., 2005. Evaluating sand and clay models: do rheological differences matter? Journal of Structural Geology, v. 27, p. 1399-1412. Withjack, M. O., Schlische, R. W., Olsen, P. E., 2010. Development of the passive margin of eastern North America - Mesozoic rifting, igneous activity, and breakup, in Roberts, D. G., and Bally, A. W., eds., Phanerozoic Regional Geology of the World. Summary & Future Work Thickness of clay layer affects deformation patterns Distribution of clay layer may affect deformation patterns Kinematic model of Orpheus rift basin Future Work The modeling results and strain analysis suggest that the internal clay layer underwent not only folding but also thickness changes during deformation. Model A (thin clay) Standard Model (Initial depth 1 cm) Model D (Initial depth 0.5 cm) Varying depth of clay layer Multiple internal clay layers Model C (thick clay) 1 2 3 5 3 km a Late Triassic ? 3 km c ROU ROU CAMP-related intrusions Buckle folds Detached thrust faults Latest Triassic - earliest Jurassic ? 3 km b Deposition of interbedded salt and salt impurites Late Triassic ? Late Rifting: Minibasins and CAMP Intrusion Middle Rifting: Upper Argo Formation Early Rifting: Lower Argo Formation ROU 4 (Left) Map showing early Mesozoic rift basins (green areas), including Orpheus rift basin, as part of eastern North American rift system formed during break-up of Pangea and general stratigraphy of the Orpheus rift basin. The Orpheus rift basin contains Late Triassic-Early Jurasssic salt of the Argo Formation. Note the presence of salt impurities within the Argo salt. ROU: Rift-onset unconformity; BU: Breakup unconformity; AvU: Avalon unconformity: CU: Cenozoic unconformity; CAMP: Central Atlantic Magmatic Province. Yellow line is the seismic line shown in this study. (Below) Similarities between modeling results (Model A) and structures in Orpheus rift basin. Similar to the models, buckle folds in the synrift section of the Orpheus rift basin are present adjacent to a sedimentary load (i.e., minibasin). Seismic line is 1:1 at 4.5 km/s. 5 km 1 s (TWTT) North South 5 cm Prerift Postsalt minibasin Postrift Synrift salt Igneous sheets Synrift presalt Comparison with Natural Examples Boudins Overturned folds Minibasin Upright gentle folds 400 km North Atlantic Ocean North America N Orpheus Basin modified from Withjack et al. (2010) Period PERMIAN & OLDER TRIASSIC Postrift Prerift Synrift EARLY JURASSIC & YOUNGER Late Early Mid Strati- graphy Tectonic Stages AvU CU BU CAMP Mini- basin ROU Argo Salt Preliminary Modeling Results: Models with various depth of internal clay Time: 5 hours 5 cm Standard Model (Putty:Clay = 4:1) Initial depth of clay layer: 1 cm Model C (Putty:Clay = 4:1) Initial depth of clay layer: 0.5 cm 5 cm Time: 5 hours 40 30 0 10 20 Extension (%) Strain analysis of the internal clay layer Line of equal value Shortening (%) 30 40 20 10 Standard Model Model A Model B Model C Strain Analysis Percentage of extension vs shortening of the internal clay layer in all models. The amount of shortening in all models is less than the amount extension. Zone of extension Zone of shortening % Extension or shortening = (Lf-Lo)/Lo x 100% Lf = Final Length; Lo = Ori