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Quantitative Evaluation of the Sea-level Drop at
the End-Permian: Based on Reefs
WU Yasheng
（Institute of Geology and Geophysics, Chinese
Academy of Sciences, Beijing 100029）
FAN Jiasong（Institute of Geology and Geophysics,
Chinese Academy of Sciences, Beijing 100029）
Abstract：The
amplitude of pre-Quaternary sea level drop, H,
can be calculated by using the formula H = D +
To, where To is the original thickness from the
top of the tidal deposits on the reef core to
the bottom of the tidal deposits on the reef
front, or to the bottom of the ancient meteoric
vadose zone, or to the edge of the mixed-water
dolostone zone. The identity and similarity
between the sea-level drop amplitudes calculated
from different reefs far away from each other
indicates that such sea-level changes are
eustatic rather than relative changes. Evidence
of an end-Permian sea-level drop has been found
on the Changxingian (i.e. the end of the
Palaeofusulina zone) reefs at Ziyun in South
China, including algal laminated deposits,
sabkha-related dolostone, desiccation cracks,
dissolution collapse breccia. According to
calculation based on the meteoric dissolution
zone of the reef-core sequence at Ziyun, Guizhou
province, the amplitude of the sea-level drop at
the end-Permian is about 89.3 m. Calculation via
the dolomitized upper part of the Changxingian
reef in Lichuan, Hubei Province, yields an 88.9
m amplitude of the sea-level drop at the
end-Permian. Comparison shows that the sea-level
drop recorded in the two distantly located reefs
may be of eustatic type. So the amplitude of the
sea level drop of the Tethys Sea at the
end-Permian might be at least 89.3 m.
Keywords：sea-level drop,
eustatic, reef, Permian, Changxingian
CLC Number：P5 Document
ID：A
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