VIRTUAL FIELD TRIP # 7 One-Day Field Trip by Boat to Atchafalaya and Wax Lake Delta Systems, LA Spring Field Trip - May 1, 2004          This trip is designed for geoscientists interested in the sedimentology and sedimentary architecture of deltas. The Wax Lake delta is part of the Atchafalaya-Wax Lake bayhead delta complex. These two bayhead deltas started being deposited in the late 1940s as a product of diversion of the Mississippi River water and sediment down the Atchafalaya River course. These deltas represent the embryonic stage of a new major delta lobe in the Mississippi River deltaic system. The Wax Lake delta has not been modified by man’s activities and represents an outstanding natural setting for studying the early stages of delta-building. LEADER: DR. HARRY ROBERTS, COASTAL STUDIES INSTITUTE, LOUISIANA STATE UNIVERSITY Click for larger view. Group photo - left to right: Row 1 (top) Tom VanWagoner, Tim Rynott, Jim Flis, Dave Domec, Paul Langlois, Dan Ruberg, Row 2 (middle) Don Rehmer, Mike Quinn, Arden Anderson, Dave Fugitt, Harry Roberts, Chris (our boat skipper), Row 3 (bottom) (seated) Barry Wawak, Ted Gard. [not pictured] - Mary Broussard, photographer.   Ted Gard's Summary of 2004 Wax Lake Outlet Delta Fieldtrip, St. Mary Parish, Louisiana The weather smiled kindly on the adventurous trippers just long enough to do a complete tour and traverse of the delta made by the Wax Lake Outlet canal. The canal is a cut between the Atchafalaya River and Atchafalaya Bay made in the late1940’s to relieve flood pressure on Morgan City. Trip leader Dr. Harry Roberts of LSU Coastal Studies Institute (CSI) told us that most of delta has built up since the 1973 flood and is still building rapidly at the present time. The delta is unmarked by human intervention and forms a great lab model for sedimentary process study. The LGS trip moved down the canal from the US 90 crossing in three CSI boats. As we approached the delta we noticed that the water depth of the canal decreased from 70’ to 16’ in less than a mile. The channels split around numerous depositional bars that are evident from the marsh and willow vegetation above the water line. The crew cut and recovered a 20’ vibracore in a weedy patch of bar. The core revealed pre-delta laminated gray bay clay capped by a shell layer. Above the shell layer was a 1’ layer of pro-delta clay topped by banded gray and reddish sandy sediments indicative of a component of Red River provenance sediments. The pro-delta clay is from the mid-1950’s. Everything above is younger up to the present. We drifted to other parts of the delta, where Harry got out of the boat (nobody followed him) and dug into the bottom to show us the sandy sediments of the emerging distributary mouth bar near the lower end of the delta. Clouds began gathering and we headed back to our launch site and parted company with LSU-CSI. As we moved up US 90 toward New Iberia the clouds let loose and never stopped until we were all well home. Many thanks to Harry Roberts, LSU-CSI and their able boatmen for conducting the trip, Stone Energy for sponsorship and drinks and to all the participants for making it a fun-filled learning experience full of cool stuff. Ted Gard   Virtual  Fieldtrip  Stops   Fieldtrip Leaders   Leave from Patterson, Louisiana.   Happy Trippers Outward Bound.   Head of Passes, Wax Lake Outlet.   Locating the Site for the Vibrocore.   Taking a Core.   Examining the Core.   Mouth Bar.   Homeward Bound - The Wax Lake Outlet & Intercoastal Canals. Click for larger view. Aerial Photo of Wax Lake Delta showing fieldtrip stops: # 2 - Head of Passes. # 3 - Vibrocore location. # 4 - Mouth bar. [Barry Wawak's photo of Harry Roberts' aerial photo.] Click for larger view. Location map of the Atchafalaya River, the Atchafalaya Basin, and both the Atchafalaya and Wax Lake Deltas. [from H.H. Roberts, et al., "An Embryonic Major Delta Lobe: A New Generation of Delta Studies in the Atchafalaya-Wax Lake Delta System," GCAGS/GCSSEPM Transactions, Vol. 53, 2003, p. 691.] Many thanks to BARRY WAWAK and TED GARD for their help with photo sequencing and captions. This virtual fieldtrip owes a great deal to TED GARD, BARRY WAWAK, and MARY BROUSSARD, who were most generous with their time, their comments, their resources. Special thanks to the MARY BROUSSARD [mb], TED GARD [tg], and BARRY WAWAK [bw] for the use of their excellent fieldtrip photographs. Lafayette Geological Society thanks STONE ENERGY for its sponsorship of this fieldtrip. LINKS Shaded Relief Map of Louisiana   Web Author: Karen W. Broussard