『Abstract
Upland and shield areas of central and northwestern Europe are
characterised by an abundance of relict weathering mantles (saprolites).
These saprolites, if accurately dated and interpreted, may serve
as an important complementary source of information about long-term
environmental history. In this paper, methods used to establish
ages of weathering mantles are reviewed, such as stratigraphic
and morphostratigraphic dating, clay mineral and stable isotope
analysis, K-Ar and cosmogenic isotope dating, particularly with
reference to European examples. The record of deep weathering
in the Mesozoic and Cainozoic is examined to explain the peculiarities
of the evidence and controls on the changing style of weathering
through time. Weathering has been a continuous process through
time, but general and local geological conditions have resulted
in different ages of preserved mantles. An apparent trend from
an earlier kaolinitic/ferrallitic style of weathering in the Mesozoic
and Early Tertiary, towards a grussic style by the end of the
Cainozoic, does not only reflect climate change, but it is also
broadly consistent with tectonic/geomorphic history and related
changes in land surface stability. Miocene and Plio-Pleistocene
saprolites, in particular, show that in different geomorphological
and lithological circumstances, different types of weathering
mantles could have evolved.
Keywords: Weathering; Saprolites; Dating methods; Europe』
1. Introduction
2. Dating weathering mantles
2.1. Stratigraphic dating
2.2. Morphostratigraphic approach
2.3. Secondary mineral interpretation
2.4. Stable isotope analysis
2.5. K-Ar and 40Ar/39Ar dating
2.6. Cosmogenic isotope dating
3. Deep weathering in the geological record
3.1. Phases of deep weathering - convention or reality?
3.2. Specific times - specific saprolites?
3.3. Weathering style changes - discussion
4. Conclusions
Acknowledgements
References