1.Packrat Midden Analysis, since late Pleist. –Sonoran Desert History (veg & climate)...

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 300- 400 ybp

– Precipitation

– Temperature

Paleo –Vegetation and –Climate of SW

At our starting point, 20,000 years ago…At our starting point, 20,000 years ago…

(40,000 years of vegetation data from…(40,000 years of vegetation data from…packrat middens)packrat middens)

1. Packrat middens- past 20,000 years1. Packrat middens- past 20,000 years

“Sonoran Desert”

22000-11000 ybp, Late Pleistocene

• Vegetation

22,000 11,000 8,000 4,000

“Sonoran Desert”

22000-11000 ybp, Late Pleistocene

• Climate relative to today:

22,000 11,000 8,000 4,000

“Sonoran Desert”

11000-8000 ybp, Early Holocene

Vegetation

22,000 11,000 8,000 4,000

“Sonoran Desert”

11000-8000 ybp, Early Holocene

• Climate

22,000 11,000 8,000 4,000

Sonoran Desert

8000-4000 ybp, Mid Holocene

• Vegetation

22,000 11,000 8,000 4,000

Sonoran Desert

8000-4000 ybp, Mid Holocene

• Climate

22,000 11,000 8,000 4,000

Sonoran Desert

4000 ybp - present, Late Holocene

• Vegetation

22,000 11,000 8,000 4,000 0

Sonoran Desert

4000 ybp - present, Late Holocene

• Climate

22,000 11,000 8,000 4,000 0

Packrat Midden Summary

for

Sonoran Desert:

Packrat Midden Summary

for

Sonoran Desert:

Graphically it looks like this…

SW VegetationSW Vegetation

And this…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