Dendroarchaeology

March 24, 2015

Background to Historical Dendroarchaeology

Dendrochronology:Dating something using tree rings.

Dendroarchaeology:Dating a crafted or assimilated wooden object or structure using tree rings to obtain a possible cutting or manufacture date that may help establish the year or range of years for use or occupation.

Historical Dendroarchaeology:The use of these dates to help infer past human behavior, activities, patterns, and lifeways during the historical period.

This technique supplies information that complements standard archaeological data from ceramics, nails, hardware, glass, etc.

Long-Term Chronologies from Around the World

Combined pine/oak Germany ID:10,461 BC

Juniper Mediterranean ID: 7020 BC

Bristlecone pine Cali ID: 6716 BC

Long-Term Chronologies from Around the WorldCornish and English oak Ireland ID: 5218 BC

Alerce Chile ID: 1634 BC

Sabina przewalskii China ID: 1580 BC

Giant sequoia Cali ID: 1229 BC

Bald Cypress SE USA ID: 372 AD

Huon pine Tasmania ID: 900 AD

1. Not all tree species can be dated via tree-ring analyses.

2. A minimum number of rings per sample is required (> 50).

3. A nearby or regional reference chronology is required.

4. Samples should be obtained from the rounded parts of the log.

5. As many logs as possible should be sampled.

6. Erosion over time can remove the critical outermost rings.

7. Logs can be replaced, re-used, or stockpiled, causing a range of years in outermost rings.

8. A later structure can be built in the same place as the original.

Methods

Methods

Ethics

1. Tree rings either date or they do not date, i.e. no “plus or minus” or “around this period.”

2. Not all samples date nor should we expect that all samples will date.

3. Dates can not be “forced” from the dendrochronologist, i.e. the wood must provide the date.

4. Dendrochronologists do not work in a vacuum – we must consult with site personnel, staff, and archaeologists.

5. We practice minimum impact sampling and leave no trace ethics.

6. What we do is laborious, tedious, time-consuming, and extremely quantitative and expensive

A Discontinuous History• Mostly because of misconceptions (the

Southeast is too mesic)

• Human impacts

• Bad sampling practices (no standard protocol exists for preserving prehistoric wood samples)

• A lack of reference tree-ring chronologies long enough to date wood from the abundant prehistoric sites

Sample Preservation

Alfred’s Cabin, The Hermitage

• Born 1815?, died 1901

• Caretaker of The Hermitage

• Guide and interpreter

• Was cabin built while Alfred was a slave or a freedman?

Alfred’s Cabin, The Hermitage

r = 0.42, n = 94, p < 0.0001

Alfred’s Cabin was completed in April to June of 1843 or soon thereafter.

-4

-2

0

2

4

1745 1755 1765 1775 1785 1795 1805 1815 1825 1835 1845

Alfred’s Cabin

Eastern Red Cedar Master

Abraham Lincoln’s Birthplace Log Cabin (1809?)Abraham Lincoln’s Birthplace Log Cabin (1809?)

Abraham Lincoln’s Birthplace Log Cabin (1809?)

Log Cabin

Reference

r = 0.55, n = 79, p < 0.0001Logs in the Lincoln cabin date to the 1840s and 1850s.

Rocky Mount Historic Site (1770–1772)

• William Cobb: one of the earliest settlers

• Earliest intact structure in TN (1770)• Revolutionary War significance• Capital of territory from 1790–1792• Regional landmark, tourism factor!

r = 0.46, n = 131, p < 0.0001The Rocky Mount structures were built from 1827 to 1830.

= 1827–1830

Rocky Mount

Reference

Rocky Mount Historic Site (1770–1772)

Chief John Ross House (1797?)Chief John Ross House (1797?)

• Built by John McDonald, 1797• Rossville, Georgia• Trail of Tears significance• Chief John Ross, 1808-1827• Regional landmark, tourism factor!

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

1720 1730 1740 1750 1760 1770 1780 1790 1800 1810 1820

Chief John Ross House (1797?)Chief John Ross House (1797?)

r = 0.29, n = 75, p < 0.0001

Piney Creek

John Ross

Culturally Modified Trees

Peel Tree Trail Tree

Provenance and Dendrochronology