AGS Monthly Meeting

November Presentation: Sedimentation rates and sediment content of Lake Lanier, implications for lakebed development and deposition

When: November 25, 2022
6:00: Social: refreshments and snacks served
6:45: Business meeting (zoom starts)
7:00: Presentation

The meeting will be in person at the Fernbank Museum and via zoom. Click on this link to join meeting via zoom.

Speaker bio:  Steve Fitzpatrick has taught geology, environmental science, and integrated science at Perimeter College of Georgia State University for 12 years. He has a master’s degree (2011) in Geology from the University of Georgia, with specialties in subsurface runoff, soil structure, and shallow field geophysics. Throughout his career Steve has conducted geological, soil science, hydrology, and general environmental academic fieldwork as well as experimental design for geology and environmental science labs. Steve is currently writing an environmental science textbook based on a an empirical natural-science approach rather than the usual social-science driven one. He is also attempting to reinvigorate a program of doctoral study, a seemingly ongoing effort. Maybe this presentation will help with that effort! Who knows? Anyway, in his spare time Steve likes to watch movies, play music, spend time with family and friends, and errantly wander around the countryside.

Abstract:  Lake Sidney Lanier is an impoundment reservoir in North Georgia, U.S.A. that was completed in the late 1950’s for the purposes of municipal use and recreation. Lake Lanier was formed when Buford Dam to the southwest of the lake was completed. The geological setting of Lake Lanier is that of deeply folded ridges and interfluves trending SW-NE set within the high-grade metamorphic rock of the Southeastern Piedmont Physiographic Province. Throughout its short history Lake Lanier has significantly altered the ecosystem, geology, and hydrology of the area. These changes have included sediment budget imbalances, altered hydrochemistry through increased resident time, anthropogenic forcing through development and contamination, and lake bottom sedimentation. Prior to Lake Lanier, sediments did not collect on the bottom of that reach of the Chattahoochee River: it did not function as a depositional basin. The entirety of the Piedmont is that of an erosive geological setting due to the trend of differential stress place upon the country rock during the development of the Appalachian Mountains ~300 Mya. The entirety of this region drains streams southward. The artificial emplacement of Lake Lanier, as well as other reservoirs in North Georgia, provides a unique setting for upland sediment deposition from upland contributions These contributions include a wide variety of naturally weathered products from a variety of metamorphic rocks north of the lake – such as amphibolite, gneiss, and schist – as well as anthropogenic contributions. Furthermore, Buford Dam is an embankment dam within a tectonically quiescent region and as such has a possible lifespan of hundreds or more years. Lake Lanier has a maximum depth of 160 feet and as such may accumulate significant layers of sediment on its bottom annually. One can reasonably assume that these sedimentary layers, over time, are being altered through something akin to early-stage diagenesis.