Chapter 08 Author: Lee Hannah

1. Chapter 08 Author: Lee Hannah

2. FIGURE 8.1 Fossils of a Laggerstatten. Laggerstatten are concentrations of well-preserved fossils that provide unique macrofossil evidence of past species assemblages. From the University of Chicago Medical Center.

3. FIGURE 8.2 Megadroughts Over Two Millennia. Megadroughts are droughts that last for more than a century. Numerous megadroughts have been documented from lake sediments in many regions of the world. Note that time runs from right to left in this fi gure. Reproduced with permission from Yale University Press.

4. FIGURE 8.3 Varve Record of the End of Younger Dryas. Varved (annually resolved) lake sediments make this highly resolved record of climate change around the Younger Dryas, Bolling, and Allerod events possible. From Landmann, G., et al. 1996. Dating Late Glacial abrupt climate changes in the 14,570 year long continuous varve record of Lake Van, Turkey. Palaeogeography Palaeoclimatology Palaeoecology 122, 107 – 118.

5. FIGURE 8.4 Milankovitch Forcing in Lignite Deposits. Interbedding driven by solar cycles is clearly evident in these lake deposits in northern Greece. From Cohen, A. S. 2003. Paleolimnology . Oxford University Press.

6. FIGURE 8.5 Monomictic, Dimictic, and Meromictic Lake Turnover. Winds, ice, and temperature conditions determine lake turnover, resulting in lakes that turnover once (monomictic), usually in fall, or twice (dimictic) — once in fall and once in spring. Meromictic lakes mix incompletely, resulting in a deep unmixed layer.

7. FIGURE 8.6 Dimensional Freshwater Food Chain Diagrams. Dr. Neo Martinez at the National Center for Ecological Analysis and Synthesis constructs three-dimensional food webs that capture the multiple trophic strategies of freshwater systems. Lower levels of the food chain are interconnected due to multiple mid-level feeders acting on primary producers. Upper levels of the food chain become progressively simpler, often converging on single top carnivores. Courtesy of Paulo C. Olivas.

8. FIGURE 8.7 Freshwater Family Accumulation in Deep Time. From Cohen, A. S. 2003. Paleolimnology . Oxford University Press.

9. FIGURE 8.8 Freshwater Family First and Last Occurrences. From Cohen, A. S. 2003. Paleolimnology . Oxford University Press.

10. FIGURE 8.9 Fossil Lake and Human Occupation Sites in the Sahara. Fossil lakes (left) in the Sahara indicate that the conditions were much moister there between 2500 and 10,000 years ago. Remains of human occupations and elephants (right) include rock art (symbols), finely worked tools, and signs of hunts. Modern elephant range is shown for comparison. From Wilson, R. C. L., et al. 2000. The Great Ice Age – Climate Change and Life . Routledge.