Beaches of Glacial Lake Agassiz

1. Beaches of Glacial Lake Agassiz 070079 Kirsten Landen December 7, 2010 Geomorphology Dr. Wiseman

2. Topics of Interest Glacial Lake Agassiz Background Information Classification of Beaches Southern Outlet Beach Descriptions Campbell & Lower Campbell Beaches Formation of Beaches Significance of Agassiz Beaches

3. Background Information Formed 11,700 year BP Red River-Des Moines ice lobe retreated north of the Hudson Bay/Gulf of Mexico drainage divide First named by Warren Upham in 1880 Lake & drainage basin covered 2million km2 Rocky Mountains to the Lake Superior Basin South Dakota to Hudson Bay

4. Background Information Total water area was 950,000km2 Maximum water extent covered 350,000km2 During a glacier advance between 9900-9500 years BP 50+ documented beaches

6. Classification of Beaches Typical beach ridge: 3-10ft above the surrounding land on the side away from the lake 10-20ft above the surrounding land on the side of the lake 165-412 feet wide Stratified sand and gravel (largest material 2-6in) Surrounding area composed of till, unstratified clay, larger boulders

7. Classification of Beaches

8. Southern Outlet Beaches Classified by four series of closely-spaced beaches Herman, Norcross, Tintah & Campbell ? ? Decreasing elevation ? ?

9. Southern Outlet Beaches

10. Southern Outlet Beaches

11. Southern Outlet Beaches: Herman Splits into 12-13 individual strands Poorly developed Especially east of the Riding & Duck Mountains Splitting occurred at 3 hinge lines Highest elevation of the southern beaches

12. Southern Outlet Beaches: Norcross Classified by four extensive closely-spaced shorelines Sometimes grouped into two main areas Northernmost area is well-developed Slight divergence Approx. 20 ft lower than the Herman Beach

13. Southern Outlet Beaches: Tintah Two pairs of beaches No definite split Wide divergence Medium elevation of the southern beaches

14. Southern Outlet Beaches: Campbell Divided into Campbell and Lower Campbell beaches Campbell is the most well-developed beach of Lake Agassiz Lower Campbell is well-developed in the north but poorer in the south No split but some slight divergence

15. Campbell Beach Most well-developed beach of Lake Agassiz Composed of gravel and sand deposits �-1mile wide and 25-30ft deep Classified by offshore barriers, berms or erosional escarpments

16. Campbell Beach Formation indicates a return of drainage to its southern outlet Lake Agassiz had temporarily been draining east Stopped with the re-advancement of an ice sheet

17. Lower Campbell Beach Well developed in the northern reaches, less so in the southern extent Classified by barrier beaches, berms and erosional escarpments Only 1.5 miles apart from the Campbell beach in the south

18. Lower Campbell Beach Formed after a 60ft drop in lake level Due to a retreat of an ice sheet which opened up a lower outlet Differential uplift started during formation Indicated by the convergence of the beaches in the south

19. Campbell & Lower Campbell Beaches

20. Formation of Beaches Unlikely that an extensive, well-developed beach can form with high levels of differential isostatic rebound Relationship of Agassiz outlets, fluctuations in ice-margins & differential rebound provided the mechanism for deepening (transgressing)& lowering (regressing) the lake And in turn, forming the beaches

21. Formation of Beaches Regression can deposit a uniform layer of sediment Often abrupt change that can interrupt accumulation Poor berms & barrier beaches Transgression creates waves that work coarse-grained sediment upslope Forms larger/extensive beaches

22. Formation of Beaches Four (Five) southern outlet beaches formed through transgression Tintah�s formation sped up by re-advancing ice at the NW outlet Campbell�s transgression controlled by isostatic rebound of the NW outlet Campbell experienced longest transgression

23. Formation of Beaches

24. Formation of Beaches

25. Significance of Agassiz Beaches Silt & clay deposits form fertile soils Agriculture Sand & gravel deposits are important sources of structural supplies Gravel pits Cultural significance Archaeological sites, First Nations burial grounds

26. Text References Fisher. (2005). Strandline analysis in the southern basin of glacial Lake Agassiz, Minnesota and North and South Dakota, USA. Geological Society of America. 117(11), 1481-1496. Johnston. Glacial Lake Agassiz. Ottawa: Geological Society of Canada, 1946. Lepper, et al. (2007). Ages for the Big Stone Moraine and the oldest beaches of glacial Lake Agassiz: Implications for deglaciation chronology. Geological Society of America, 35(7), 667-670. Neilsen. (1987). Origin & Palaeoecology of post-Lake Agassiz raised beaches in Manitoba. Canadian Journal of Earth Sciences, 24(7), 1478-1485. Rayburn & Teller. (2007). Isostatic rebound in the north-western part of the Lake Agassiz basin: Isobase changes and overflow. Paleogeography, Palaeoclimatology, Palaeoecology, 246(1), 23-30. Teller. (2001). Formation of large beaches in an area of rapid differential isostatic rebound: the three-outlet control of Lake Agassiz. Quaternary Science Reviews, 20(15), 1649-1659. Teller, Glacial Lake Agassiz. Canada: Geological Society of Canada, 1983. Upham. Upper Beaches & Deltas of Glacier Lake Agassiz. Washington: Government Printing Office, 1887.

27. Image/Diagram References Sl. 5: Maximum Extent & Major Features of Lake Agassiz Teller, Glacial Lake Agassiz. Canada: Geological Society of Canada, 1983. Sl. 7: Typical Section Across a Beach Ridge at Lake Agassiz Warren Upham, Upper Beaches & Deltas of Glacier Lake Agassiz (Washington: Government Printing Office, 1887), page 11. Sl. 9: Relative Elevations of Lake Agassiz Beaches Teller. (2001). Formation of large beaches in an area of rapid differential isostatic rebound: the three-outlet control of Lake Agassiz. Quaternary Science Reviews, 20(15). Sl. 10: Southern Extent of Lake Agassiz Fisher. (2005). Strandline analysis in the southern basin of glacial Lake Agassiz, Minnesota and North and South Dakota, USA. Geological Society of America. 117(11). Sl. 19: Aerial Photography of Campbell Beaches Rayburn & Teller. (2007). Isostatic rebound in the north-western part of the Lake Agassiz basin: Isobase changes and overflow. Paleogeography, Palaeoclimatology, Palaeoecology, 246(1). Sl. 23: Shoreline Development in a Basin Undergoing Isostatic Rebound Teller. (2001). Formation of large beaches in an area of rapid differential isostatic rebound: the three-outlet control of Lake Agassiz. Quaternary Science Reviews, 20(15). Sl. 24: Relative Changes in Lake Level & Overflow Outlets Used Teller. (2001). Formation of large beaches in an area of rapid differential isostatic rebound: the three-outlet control of Lake Agassiz. Quaternary Science Reviews, 20(15).

28. Questions?