1.Packrat Midden Analysis, since late Pleist. –Sonoran Desert History (veg & climate) 2.Alluvial Stratigraphy, since early Holocene –Dry-wet and/or warm-cool periods 3.Dendrochronology, since ybp –Precipitation –Temperature Paleo –Vegetation and –Climate of SW
At our starting point, 20,000 years ago…
(40,000 years of vegetation data from… packrat middens) 1. Packrat middens- past 20,000 years
“Sonoran Desert” ybp, Late Pleistocene Vegetation 22,00011,0008,0004,000
“Sonoran Desert” ybp, Late Pleistocene Climate relative to today: 22,00011,0008,0004,000
“Sonoran Desert” ybp, Early Holocene Vegetation 22,00011,0008,0004,000
“Sonoran Desert” ybp, Early Holocene Climate 22,00011,0008,0004,000
Sonoran Desert ybp, Mid Holocene Vegetation 22,00011,0008,0004,000
Sonoran Desert ybp, Mid Holocene Climate 22,00011,0008,0004,000
Sonoran Desert 4000 ybp - present, Late Holocene Vegetation 22,00011,0008,0004,000 0
Sonoran Desert 4000 ybp - present, Late Holocene Climate 22,00011,0008,0004,000 0
Packrat Midden Summary for Sonoran Desert: Packrat Midden Summary for Sonoran Desert:
Graphically it looks like this…
SW Vegetation And this…
Alluvium: (n) Alluvial: (adj) Stratigraphy: (n) Alluvial stratigraphy: Recent geology (Pleistocene-Holocene). 2. Alluvial Stratigraphy of the SW: Definitions…
2. Alluvial Stratigraphy of the SW (Holocene)
Alluvial Stratigraphy sites… “Filling in” DEPOSITION “carving out” EROSION
Replication Why are sediment sites so common in SW?
It’s like a jig- saw puzzle Distinct layers –Color –Texture –Fossils Separated by time –Erosion –Soil In The Field Layers C-14 dated
Alluvial History: Climatic Interpretation Summary
3. Dendrochronology (past 300 – 400 years) Dendroclimatology Subdiscipline of dendrochronology –Reconstruct past climate –Heavily replicated Within sites Within regions
Dendrochronology recap…
We’ve Seen This Before
Summary Paleoenvironments of SW