Rock art dating by 230Th/234U analysis: an appraisal of Chinese case studies

Abstract

A reconsideration of the application of 230Th/234U analysis to thin accretionary skins of re-precipitated carbonate to secure minimum or maximum ages for physically related rock art suggests that the controversy it has created can be resolved. A program to test the method’s results indicates that such calcite skins tend to yield age estimates that are too high, particularly from Pleistocene samples. Although the controversy about such results has escalated in recent years, it had initially become apparent several decades ago. Here, two case studies of Chinese rock art, in Heilongjiang and Yunnan Provinces, are presented. Potential error sources accounting for the discrepancies are proposed. Some cautionary measures are presented to prevent the promotion of sensational but ultimately erroneous rock art age estimates deriving from this method.

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ORIGINAL PAPER
Rock art dating by
230
Th/
234
U analysis: an appraisal of Chinese
case studies
Tang Huisheng
1
&Robert G. Bednarik
1,2
Received: 3 July 2020 /Accepted: 17 December 2020
#The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature 2021
Abstract
A reconsideration of the application of
230
Th/
234
U analysis to thin accretionary skins of re-precipitated carbonate to secure
minimum or maximum ages for physically related rock art suggests that the controversy it has created can be resolved. A
program to test the method’s results indicates that such calcite skins tend to yield age estimates that are too high, particularly
from Pleistocene samples. Although the controversy about such results has escalated in recent years, it had initially become
apparent several decades ago. Here, two case studies of Chinese rock art, in Heilongjiang and Yunnan Provinces, are presented.
Potential error sources accounting for the discrepancies are proposed. Some cautionary measures are presented to prevent the
promotion of sensational but ultimately erroneous rock art age estimates deriving from this method.
Keywords
230
Th/
234
Udating.
14
C dating .Rock art .Cross-checking .Blind testing
Introduction
The rock art of Heilongjiang Province, the northernmost state
of China, was recently introduced (Tang et al. 2020). The
primary significance of this paper was not, however, that it
was the first international report of Heilongjiang’s rock art but
that it discussed rock art dating methodology and, in particu-
lar, its examination of
230
Th/
234
U analysis. In recent years,
rock art dating by that method has caused a significantly acri-
monious but likely unnecessary debate. The present paper
discusses the debate and hopefully provides the impetus to
resolve the unwarranted controversy by showing how to con-
structively settle it.
Tang et al. (2020) reported the rock paintings at nine sites
and site complexes across northern Heilongjiang Province. In
most sites, these assemblages have relatively small numbers
of motifs, generally < 100. Located on cliffs, they have limited
or no protection from the weather. Thus, they have been as-
sumed to have been painted relatively recently. The limited
literatureavailable on the longevity for rock paintings exposed
to the elements (e.g. Trezise and Wright 1966; Donaldson
2012:23–29) suggests that preservation is severely reduced
relative to well-sheltered situations, especially deep caves.
Rock paintings exposedto precipitation are thought to survive
for only a few centuries in most cases. The absence so far of
petroglyphs in Heilongjiang is puzzling, because they are
quite common in neighbouring Inner Mongolia and on the
Siberian side of the Amur River, which forms the border with
Russia.
At two sites, Tayuan Rock Art Site, Xinlin District, and
Tiantaishan Rock Art Site, Jagedaqi Forest, microerosion data
provided maximum age estimates for rock paintings. In both
cases, the painting pigments were applied to small panels that
had formed when slabs exfoliated from granite tors in geolog-
ically recent times. The time for such an unloading event can
be estimated from the amount of microscopic rounding
(micro-wane formation) at fracture edges on quartz or feldspar
crystals that fractured along the edge of the new surface
formed. The paintings on such new panels must be more re-
cent than the time the slabs detached. The findings were par-
ticularly important at Tayuan, because one of its two schemat-
ic zoomorphs had been suggested by local archaeologists to
depict a rhinoceros. If that were correct, it would imply that it
portrays a woolly rhinoceros, an extinct Pleistocene species.
*Robert G. Bednarik
robertbednarik@hotmail.com
1
International Centre of Rock Art Dating (ICRAD), College of
History and Culture, Hebei Normal University, No. 20
Nanerhuandonglu, Yuhua District, Shijiazhuang, Hebei Province,
China
2
International Federation of Rock Art Organisations (IFRAO),
P.O. Box 216, Caulfield South, Melbourne, VIC 3162, Australia
https://doi.org/10.1007/s12520-020-01266-0
/ Published online: 8 January 2021
Archaeological and Anthropological Sciences (2021) 13: 19
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