Table 4 Grading scheme for 14C dates for plant and aquatic materials, and accuracy of chronological determination.

From: A dataset of scientific dates from archaeological sites in eastern Africa spanning 5000 BCE to 1800 CE

Short- vs long-lived plant material

Grade

Sample from taxonomically identified short lived plant parts: Annual seeds, leaves and twigs

A

Sample from taxonomically identified long lived plant parts: Perennial seeds, leaves and twigs

B

Unknown/unreported: Taxonomically unidentified plant parts: Charcoal

C

Aquatic radiocarbon reservoir effects

Fully terrestrial sample

A

Aquatic sample

B

Unknown/humans or other animals that may have consumed aquatic foods

C

Accuracy of chronological determinations (Pre-treatment protocol)

Published after 1988. The ultrafiltration method and AMS were introduced around 1988.

A

Published between 1972 and 1988. The Longin method was introduced in 1971.

B

Samples published prior to 1972

C

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