414
N. Gorelikova, N. Patyk-Kara, I. Chizova, J.Plakht, A. Sivtsov
2
The Goal
Many papers are devoted to investigating the potential of using chemistry rock
varnish for the elucidation of environmental formation, climatic changes and
dating of geological events in the Quaternary period. For these purposes, researchers have used different parameters, such as pair cation ratio, complicated
cation ratio, cosmogenic stable nuclides, organic matter, etc. These attempts and
different approaches were summarized by Dorn and Fillips (1991). The problem
of dating Quaternary events is very complicated because there are no reliable
methods of determination of geological age younger than 2000 years. Furthermore, the evolution of geomorphic events which change in space and time often
eludes interpretation. When dating, one cannot always use stratigraphic markers, such as the K-Ar age of lava flows, 14C data of charcoal intercalated with deposits, uranium-series, paleomagnetic data, fissiontrack, stable isotopes, thermoluminescence data, and others. Suitable material for stratigraphic dating is
lacking for the most geomorphic processes. Furthermore, stratigraphic age control cannot be performed for erosional landforms. In this study we also attempted to use different approaches and various special ratios, such as Fe:Mg, Fe:Ti,
Fe:Mn, Fe+ Mg/Mn, etc. However, these operations did not give positive results,
i.e. they did not show a clear-cut relation between the chemistry of rock varnish
and geological age. Thus only models designed on the basis of linear programming using all possible combinations of ratios and products provided relative
and absolute dating of geomorphic surfaces.
Rock-varnish coating on cobbles from geomorphic surfaces and exposed deposits in arid environments is an effective medium for dating over the range of
several thousands to some million years. This chapter shows an attempt to use
rock varnish from Makhtesh Ramon for dating various geomorphic levels and to
establish quantitative models of relationships between rock-varnish coating
chemistry and its age-dependent characteristics. The focus of our study is on
creating foolproof methods of rock-varnish dating assessment and revealing age
relations between geomorphic levels. As compared with rock varnish from other
regions, for example Death Valley (Dorn et al. 1987), the patina of Makhtesh Ramon is considerably thinner, which is the result of the lack of maturity of these
formations. It has posed procedural difficulties in the analysis of rock-varnish
coating. Therefore, a special technique of microprobe analysis for unpolished
surfaces was created by G.Nechelustov. This procedure analyzed the chemical
composition of extremely thin coatings of rock varnish from Makhtesh Ramon.
Element concentrations in rock varnish coating on cobbles from different geomorphic levels of Makhtesh Ramon in the Central Negev (Israel), formed from
2 million years to 3000-4000 years B.P., were determined.
Since the mobility of some elements (Fe, Mn, Ti, Si) making up the bulk of
rock varnish is closely connected with environmental change, it is supposed that
coating composition can be an indicator of climatic conditions. Among other
things, the ratio between Mn and Fe is higher in semiarid environments and in-
N. Gorelikova, N. Patyk-Kara, I. Chizova, J.Plakht, A. Sivtsov
2
The Goal
Many papers are devoted to investigating the potential of using chemistry rock
varnish for the elucidation of environmental formation, climatic changes and
dating of geological events in the Quaternary period. For these purposes, researchers have used different parameters, such as pair cation ratio, complicated
cation ratio, cosmogenic stable nuclides, organic matter, etc. These attempts and
different approaches were summarized by Dorn and Fillips (1991). The problem
of dating Quaternary events is very complicated because there are no reliable
methods of determination of geological age younger than 2000 years. Furthermore, the evolution of geomorphic events which change in space and time often
eludes interpretation. When dating, one cannot always use stratigraphic markers, such as the K-Ar age of lava flows, 14C data of charcoal intercalated with deposits, uranium-series, paleomagnetic data, fissiontrack, stable isotopes, thermoluminescence data, and others. Suitable material for stratigraphic dating is
lacking for the most geomorphic processes. Furthermore, stratigraphic age control cannot be performed for erosional landforms. In this study we also attempted to use different approaches and various special ratios, such as Fe:Mg, Fe:Ti,
Fe:Mn, Fe+ Mg/Mn, etc. However, these operations did not give positive results,
i.e. they did not show a clear-cut relation between the chemistry of rock varnish
and geological age. Thus only models designed on the basis of linear programming using all possible combinations of ratios and products provided relative
and absolute dating of geomorphic surfaces.
Rock-varnish coating on cobbles from geomorphic surfaces and exposed deposits in arid environments is an effective medium for dating over the range of
several thousands to some million years. This chapter shows an attempt to use
rock varnish from Makhtesh Ramon for dating various geomorphic levels and to
establish quantitative models of relationships between rock-varnish coating
chemistry and its age-dependent characteristics. The focus of our study is on
creating foolproof methods of rock-varnish dating assessment and revealing age
relations between geomorphic levels. As compared with rock varnish from other
regions, for example Death Valley (Dorn et al. 1987), the patina of Makhtesh Ramon is considerably thinner, which is the result of the lack of maturity of these
formations. It has posed procedural difficulties in the analysis of rock-varnish
coating. Therefore, a special technique of microprobe analysis for unpolished
surfaces was created by G.Nechelustov. This procedure analyzed the chemical
composition of extremely thin coatings of rock varnish from Makhtesh Ramon.
Element concentrations in rock varnish coating on cobbles from different geomorphic levels of Makhtesh Ramon in the Central Negev (Israel), formed from
2 million years to 3000-4000 years B.P., were determined.
Since the mobility of some elements (Fe, Mn, Ti, Si) making up the bulk of
rock varnish is closely connected with environmental change, it is supposed that
coating composition can be an indicator of climatic conditions. Among other
things, the ratio between Mn and Fe is higher in semiarid environments and in-