(BEING CONTINUED FROM 9/07/15)
METHODS FOR RESEARCH OF LUMINESCENCE OF CAVE MINERALS
AND SPELEOTHEM RECORDS OF THE PALEOCLIMATE
AND SOLAR ACTIVITY IN THE PAST
Y.Y.Shopov, Georgiev L. ,Tsankov L.,V.Dermendjiev ,G.Buyukliev (Bulgaria)
The Laser Luminescent Analysis of Speleothems was proposed as a technics for investigation on mineral forming environment. The Visual Luminescence Analysis was used as a method for investigation on climate changes during Quaternary. But those methods have a resolution which is insufficient to clarify the cyclicity of the short-time variations of the climate and solar activity (SA). For this purpose we proposed the method Laser Luminescent MicroZonal Analysis (LLMZA) with very high resolution.
Up to now the available information for cycles of the solar activity are from different approaches,such as direct measurements for 240 years;data from dendrochronology for 7400 years ago with resolution 1 yr; and 14C data for the last 10000 yrs. After calibration with this data,the LLMZA method can be used for obtaining such information with higher resolution (up to 3 days) up to several millions years ago (the age of the oldest flowstones).
METHODS FOR RESEARCH ON LUMINESCENCE OF CAVE MINERALS
We elaborate 3 methods (table 1),4 technics (table 2) for research of speleothems and 3 appratus for using directly in caves. They allows considerable enlargement for types and quality of the obtainable information and decrease to minimum quantity of the samples necessary for laboratory measurements.
The most simple method for luminescent research,which can be used by every caver is IPP. Slides obtained by using this method can be developed by CSS for preparation of spectra of phosphorescence. In speleology CSS is appplied for preparation of spectra of diffuse reflectance and luminescence (at developing of slides obtained by IPL method). It is intended for research of widelines spectra, such as the luminescence of all speleothems formed at normal cave conditions (at temperature below 40° C).
This methods are foundations of the International Programme for research of “Luminescence of Cave Minerals of the World” of the Commission of Physical Chemistry and hydrogeology of the International Speleological Union of UNESCO, leaded by Y.Y.Shopov.
The aim of this programme is the elaboration of a system for express diagnostics of the Luminescent Cave Minerals (CM),by photographing its luminescence with IPP and obtaining the spectra with CSS. The determination of the spectra of L of all luminescent CM (which is the object of this programme) is necessary for this purpose. The LLMZA investigations are object of this programme too. An advantage of this programme is its possibility for easy collection of information for CM and conditions of its formation in caves around the world from non-skilled cavers and processing of the information with standardized technics.
First stage of the Programme is the preparation of slides of phosphorescence (P) of the CM (with IPP) in the caves. Determination of typomorphic types of luminescence of CM in caves will be produced.
Second stage: 1. Spectral development of slides by CSS method, 2. Indentification of obtained spectra by comparison with known spectra of luminescence. 3.Receiving of sample of the mineral from the author, if the spectrum isn’t known. Preparation of spectra of luminescence of the CM with different excitation for determination of the luminescent centre. 4.Perfect phase diagnostics of the mineral with X-ray diffraction and DTA,DTG and TG analysis . 5.Laboratory investigation on the changes of mineral forming conditions,climate and solar activity with LLMZA are produced parallelly.
Third stage: 1.Preparation of “Atlas of Luminescence of Cave Minerals” for diagnostics of CM with LSPA. 2.Edition of the book “Luminescence of Cave Minerals of the World” including this Atlas.This book will contain Search Manual for diagnostics of cave minerals and reviews of investigation of its luminescence.
Table 1. New Methods for Research of the Luminescence of CM
Method Authors obtainable information
I. Impulse Photography Shopov, determination of minerals,registration
of Luminescence (IPL) Tsankov of colour & zonality of fluorescence &
1.Photography of (1984) phosphorescence and its spectra,UV-photography,
phosphorescence (IPP) extraction of single mineral samples.
2.Photography of flu- Shopov, changes of chemism of the mineral-forming
orescence & phospho- Grynberg solution, Climate and Solar Activity
rescence (IPFP). (1985) variations during Quaternary.
II.Colour Slide Spec- Shopov, widelines spectra of phosphorescence.
trophotometry (CSS) Georgiev fluorescence and diffuse reflectance
(1986) of mineral.Spectra of quick processes.
III.LASER Luminescent Shopov. Y Microzonality of luminescence,changes
Microzonal Analysis (1987) of mineral-forming conditions. Climate
(LLMZA) & Solar Activity variations during
Quuaternary (with resolution up to 3
days ).Speleothem dating (with accuracy
1 year).Interruptions of speleothem growth.
Table 2.New Technics for Research of the Luminescence of CM
Technics Authors obtainable information
1.LASER Luminescent Ugumori Quantity of activating ion zonality of
Zonal Analysis (LLZA) (1980) luminescence of the speleothem kind of
2.Direct Spectroscopy Shopov luminescent ion ,changes of chemism of
of Luminescence (DSL) Spasov mineral-forming solutions, determination
(1983) of genetic type of the deposit, selection
3.Direct Spectrogra- Shopov, Registration of spectra of fluorescence
phy of luminescence Tsankov & phosphorescence directly in caves,
(DSGL) (1984) luminescent ion and its valency, coor-
dination and local symmetry,diagnostics
of CM & all from DSL.
4.Luminescent spect- Shopov Determination of phase composition of the
ral Phase Analysis et al. speleothem by spectra of its luminescence.
5.LASER Luminescent Shopov Such as DSGL for collomorphyc aggregates
Spectral Analysis of Kostov of minerals and powders.
THE ZONALITY OF LUMINESCENCE OF CAVE FLOWSTONES AS
INDEX OF THE CLIMATE AND SOLAR ACTIVITY IN THE PAST
The luminescence of the calcite speleothems is activated usually by organic admixtures. The luminescent centers in cave flowstones are organic molecules (like humic and fulvic acids ) of products of biogenic processes in plants, growing over but penetrating into cave . The quantity of this products as the result of photosynthesis depends strongly on the solar irradiation. Therefore intensity of luminescence of the microzones in cave flowstones is determined mainly by the SA during the formation corresponding zone. By this way the curves of changes of the intensity of luminescence of flowstones along the axis of their growth presents curves of changes of the SA versus the age of rings in the flowstone. After formation of the corresponding zone it is safe from further action and safe for information of the SA during its formation.
Molecular admixtures in the flowstone luminescence at Laser irradiation of its polished section. If the growth rate of the flowstone is known, the curve of intensity of its luminescence in dependence of the distance from the surface will present a time series of the zonality of its luminescence. The time series obtained are result of SA and Paleoclimatic variations.
Density of blacking of the emulsion of the negative ,which is proportional to the concentration of luminescent organic molecules (intensity of luminescence) is placed on the axis of ordinates, and the number of the measurements (pixels, by which age can be determined, because distance from the surface is proportional to the age of the flowstones and 1 pixel is a time step of the series ) is placed on the abscissa axis.
For speleothems from the temperate climatic zone the paleoclimate have influence only over the width of the zones. Only in one cave in desert region, a speleothem with growth rings , which show the 11-yrs solar cycle were found.
We can reliably determine the annual rings in the sample using LLMZA at resolution of 5 pixels/yr.If the annual growth rate of investigated part of the speleothem were constant we can date the sample by authocorrelation of its luminescent time series. By power spectral analysis of the luminescent time series of dated sample we can obtained the annual growth rate of this part in the sample to obtained the age of it .
The LLMZA method allows possibility to obtain time series with high resolution (up to 125 points per yr) and very long time intervals (probably of some million years). Preparation of time series with very different resolution (which can vary more than 1000 times) and different periods become available with the elaboration of this method.
By power spectral analysis of a luminescent time series (shown at fig 1.B) we show convincingly the reality of cyclicity with periods of 55,95,180,275,390,550,930,1170,2340 and 3350 yrs.
Periods of 22,11, (13,3; 10,4 and 8,8), 1 and 2 yrs were determined by power spectrum of time series with 125 px/yr.
Fig.1. A: Estimation of the paleotemperature deviations of the hotest month in atlantic parts
of the northern hemisphere, at 60- 70° latitude by Zubakov
B: luminescent time series of a Bulgarian flowstone
for the last 35000 yrs, with resolution of 934 yrs/px
FLOWSTONES FOR LLMZA INVESTIGATIONS
Most suitable for dating by this method are the calcite polycrystaline speleothems having strongly pronounced zonality of their luminescence .Best results are obtained from flowstones from the shallow parts of the caves withactive air exchange, because climatic variations influence mostly on them. In speleothems from big depth only 350 years cycles of the solar activity and slow climatic variations could be traced, because climatic variations in depth are small and influence very weak on the flowstone growth. It is necessary to identify the spectra of luminescence of the sample , before applying this method. Taking in account ,that the period of cyclicity of the solar activity is constant, if the growth of the formation has been persistent from a certain period till now, this method can be used as method for dating from the number of rings due to cycles of the same type (like the dendrochronology) in this interval. However the accuracy of such dating is 1 year, independent from the age. Interruptions of the growth in the curves reflect as sharp places in the intensity variation of the luminescence in the sample.
(TO BE CONTINUED)