Thursday 9/8 Notes Tree-ring crossdating activity due Tuesday 9/20 Required Reading: Pack rat Historians Packrat Blues: http://www.youtube.com/watch?v=rqqvj952pxm BOOK O DAY last thurs Mike Baillie BOOK O DAY today Steven Hannon TODAY: Paleoenvironmental Methods How to know what environments were like in the past Repeat Photography http://biology.usgs.gov/luhna/chap9.html Packrat midden analysis http://www.sciencenews.org/articles/20050924/fob7.asp Palynology (Pollen analysis) http://www.ncdc.noaa.gov/paleo/webmapper-pollen.html Dendrochronology http://web.utk.edu/~grissino/ **********Uniformitarianism**************** ***********Modern homework*************** 1
Repeat Photography Same camera angle, time of year, time of day, etc. Limitations:????? Acoma: 1899 Photo: Jackson 1899 Tumamoc 1906 Acoma: 1977 Tumamoc 1986 Photo: Malde 1977 http://wwwpaztcn.wr.usgs.gov/tumaplot/plot16.html Repeat Photography in Tucson Silver Lake 1891 & 1982 West Branch, Santa Cruz 1904 & 1981 Photos by: above 1891 unknown; below Turner and Betancourt 1982 Photos by: above, unknown 1904; below Turner and Betancourt 1981 2
Rodent, Neotoma 21 species, 5-6 in the Southwest US Range from Canada to Nicaragua Arid-land dwellers Herbivorous cacti, succulents, seeds, fruits Den or midden builders Paul S. Martin Eeek! It s world famous Paleoecologist Paul S.Martin 3
Modern Midden Ecology Composed of: Plant materials Detritus (mammal dung) Biological debris Protection from predators Thermoregulation of inner den Collect stuff up to 50-100 meters from midden Individual rat middens collected over several years; reoccupied Things you might find in a SW packrat midden Midden Preservation Cemented with concentrated urine Crystallized urine forms amberat Preserve ancient packrat middens Biological artifacts Arid lands, dry cave environment allow for preservation Oldest date 40,000 50,000 ybp, 14 C dated Dissolve in water to analyze. 4
Principle of Uniformitarianism Current processes operate now as in past (for example: 1 ring/year) Modern midden has cactus parts, reflect modern vegetation Therefore, if paleo-middens have pine parts, paleo-vegetation had pine Absolute conditions may be different No Analog Problem How Well Do Middens Reflect Environment? Do modern homework Watch packrat behavior Measure what they collect, where Associate with existing vegetation Dietary preferences can bias collection Specialists versus generalists Biases mostly in proportions Species richness reasonably well reflected Packrat Middens in the Southwest Sample size---lots! 5
?? Based on Packrat Midden Analysis 6
Interpretation Paleoclimatic Reconstruction: Spruce-fir Today: 2800 m elevation Up to 1000 mm ppt Cold and wet 20,000 ybp: at 2300 m Cold and wet In general, cooler and wetter then versus now Principle of Uniformitarianism applied. Palynology The study of pollen grains as an aid to the reconstruction of past environments. Pine Sunflower Sunflower, morning glory, hollyhock, primrose, castor bean http://www.ncdc.noaa.gov/paleo/pollen.html http://www.ncdc.noaa.gov/cgi-bin/paleo/webmapper.cgi Palynology: Collection and Issues Collection: Cores from lakes & bogs Dirt from stratigraphic units Issues: Preservation Contamination A lake and peat bog in the White mtns of Arizona Representativeness??? Do Modern homework!!! local ecology, pollen rain, seasonality 7
Dendrochronological Reconstruction Sample Types: Living Trees Dead wood Archaeological Uses: Reconstructing Precipitation and Temperature Gretel dendro: http://www.youtube.com/watch?v=tfznp09lkhk 8
Dendrochronological Reconstructions: Issues All Samples: species, age, sensitivity Archaeological Samples: Original provenience Reconstruction Methods Crossdating EVERY ring Measuring EVERY ring to the nearest.01mm (ring width) Modern Dendroclimate Analysis Statistically associate ring-growth variation with weather data Meteorological record ~100 years old Narrow ring today = dry year Invoke Uniformitarianism Narrow ring hundreds of years ago = dry year back then Interpret wet-dry and/or cool-warm periods. 9
WARM COOL DRY WET 10
Dendro Sample Size lots! Paleoenvironmental Reconstructions Unifying concepts: Replication/repetition Lots of samples Wide spatial coverage Modern homework analysis Uniformitarianism. Activity 1: Issues?? Try skeleton plotting for yourself Fill in page with text: Insightful observations on crossdating See someone for help i.e. office hours 11