Glacial Flooding & Disaster Risk Management Knowledge Exchange and Field Training July 11-24, 2013 in Huaraz, Peru HighMountains.org/workshop/peru-2013
What prevents to make a reliable long-‐term forecast of glacial and climatic changes in Central Asia? Paleoglaciological base for long-‐term forecasting from new starting positions by the example of the Tien Shan, Pamir and Himalayas Vladimir I. Shatravin Tien Shan High-‐Mountain Scientific Center of National Academy of Sciences of the Kyrgyz Republic E-‐mail: Shatravin@yandex.ru What prevents to make a reliable long-‐term forecast of glacial and climatic changes in Central Asia? Deep contradictions which have place in quaternary geology and paleoglaciology prevent from making a reliable long-‐term forecast. During INQUA (International Union for Quaternary Research) in 1957 was made a conclusion: “The request on stratigraphic scale of Quaternary period sent to 22 countries received 22 different responses”, and in Congress hold in 1973 was stated that the situation did not change to a better . By now, 40 years later, the situation did not become better. Definitely this is the result of deep contradictions, if they are not eliminated then all attempts to make long-‐term forecast will be perspectiveless. Researchers have been doing paleoglacial reconstructions of the Quaternary for over 100 years. However, they have not definitely established even the number of Pleistocene glaciations on Earth, and have not clarified the very nature of Holocene glaciation. Tien Shan and Pamir are not exception in this regard. The existing paleoglacial information for these regions is fragmentary and quite contradictory. In general, this subject is a big informative mess. Nowadays there are a lot of highly contradictive paleoglaciological schemes, for the Holocene inclusively. Among the lasts there is a model of stadial degradation of the Holocene glaciers and the model of their quasistationary states, implicating relative stability of climate in the Holocene. General reasons of contradictions We have established the general reasons which are mentioned below: 1– the incorrect genetic typing of moraines and pseudomoraines which is traditionally carried out. 2– the lack of reliable absolute datings of moraines. 1. Incorrect genetic typing of moraines and pseudomoraines [4, 5-‐8]. As main climatic and stratigraphic marks of high mountain regions researchers use not only true moraines but pceudomoraines, improperly take them for moraines. For the Tien Shan, Pamir and partly for the Himalayas, on the base of developed by us quantitative facial-‐ lithological indicators (geochemical, granulometric and others), it was determined that all morphological formations of mountain areas, traditionally taken for early-‐ and Middle Pleistocene moraines, as well as significant part of such formations taken for Late Pleistocene moraines, in fact are Late Pleistocene-‐Holocene pceudomoraines, which true
genesis is gravitational; they are represented by wide-‐spread landslides (by widely developed landslides). This finding allowed us to reveal the very dame “root of evil” which makes difficulties and unresolved contradictions during paleoglaciological reconstructions of quaternary period, stratigraphical partition and correlation of quaternary deposits of high mountain areas with all ensuing consequences of paleoglaciological and geological direction. We made such conclusion on the basis of pattern regularities determination for glacial (with formation of moraines) and gravitational (with formation of pseudomoraines) lithogenesis. Particularly it was established that glacial and gravitational types of lithogenesis proceed in exactly opposite geochemical conditions: first of them is in reductive geochemical conditions, and the second is in oxidizing conditions. The photo shows – examples of true moraines and pseudomoraines. gl Hs – Holocene moraines. gl Ps III – Late Pleistocene moraines. gr Ps III-‐Hs – pseudomoraines (delapsive gravitational developments of late Pleistocene and Holocene age). Fe2+, Fe3+ -‐ geochemical facies of ferrous oxide and iron oxide accordingly. Moraines and pseudomoraines in the valley of Con-‐Aksu river (Noth Tien Shan). The arrows (here and below) show the direction and slumping area of polygenetic slope,s deposits that formed pseudomoraines. In this case from traditional perspective gr Ps III-‐Hs are as moraines of Middle Pleistocene age. Pseudomoraines in Alay valley (North Pamir). From traditional perspective they are as Late Pleistocene moraines.
Pseudomoraines of the Central Pamir. From traditional perspective they are as Late Pleistocene moraines.
Pseudomoraines in downstream of Muksu velley (North-‐Western Pamir). The symbol gr (dl) shown in figure is taken as the ultimate classic and coastal Pleistocene moraines of Fedchenko’s glacier. Terraces claim to be ephemeral terraces of coastal sedimentary moraines. For deposits of terraced "moraines" there were received some RTL-‐datings of 260-‐180 thousand years, allegedly correspond to the Middle Pleistocene. According to the facio-‐lithological researches of the author it is pseudomoraines in the form of huge landslide blocked Muksu river; terraces -‐ this river terraces formed on the substrate landslides. Moraines and pseudomoraines in Khumbu valley (Himalayas).
2. About the lack of reliable absolute datings of moraines [5-‐8]. Traditionally applied physical methods of absolute dating (14С, TL, OSL and 10Ве) do not allow to receive reliable dating of moraines. Dating of pseudomoraines, taking for moraines by mistake, leads to disinformation. Radiocarbon method of dating. Moraines were not dated by this method because in moraines were not found necessary autochthonous organic matter and even there were no possibilities to find it there. Due to this all radiocarbon datings of moraines were received exceptionally by allochthonous organic matter or autochthonous, found not in moraines but neighboring deposits, not of glacial genesis. Meanwhile, there is unresolved question – to what extent datings are younger or older then moraines. Use of surface soil for such radiocarbon method leads to paradox. Thermoluminescent dating of moraines. Thermoluminescent dating of moraines (as well as received by the method of OSL, which represent kind of TL method) should be considered as doubtful according to the below mentioned reasons: -‐ the very method of TL-‐dating is at the development stage, and it is developed exclusively for loess deposits;
-‐ according to interlaboratory control tests, the margin of error of this method comes up to 300-‐400% ; – except datings variations there is significant overstating (can be more in 10 times) of ages towards C-‐14 datings; – the main and absolutely insurmountable disadvantage of TL and OSL-‐methods of dating is uncertainty of “null moment” from which dated time of underground disposal (from radial cosmic energy) of material for such dating (quartz or feldspathic grains). Method of cosmic isotopes (10Ве). Impracticability of this method for dating of mraines also determined by “null moment”. Therefore, the use of such dates is only producing more mess in this subject. How to eliminate reasons of contradictions? 1. Difference between moraines and pseudomoraines [3, 4]. For reliable differentiation of moraines from pceudomoraines we received genetic features of these sediments in the form of quantitative facial-‐lithological indicators (geochemical, granulometric). In order to differentiate moraines from pseudomoraines of mountain areas we have received reliable genetic traits of these deposits in the form of the below indicated quantitative facio-‐ lithological figures. Geochemical figures. Iron oxide/protoxide ratio (protoxidic coefficient on ferrum) К= Fe2O3/FeO These figures are: - moraines К = 0,03 -‐: 0,07 - pseudomoraines К = 0,3 -‐: 1,0 Granulometric figures. Degree of clay content S=<0,005/(1-‐0,005) – correlation of fractions percentage <0,005 mm and 1 -‐ 0,005 mm, where <0,005 mm– clay fraction, 1 -‐ 0,005 (mm). These figures are: - Holocene moraines S= 0,078 - Pleistocene moraines S= 0,107 - pseudomoraines S= 0,159 True to type exposure of moraine and pseudomoraine. Moraine deposits are of blue and whitish color, which corresponds to geochemical facies of 2+ ferrous iron (Fe ). The deposits of pseudomoraine are of red-‐brown color, which corresponds to geochemical facies of iron oxide (Fe3+). Mineral grains of moraines (Fe2+) and pseudomoraines (Fe3+) under the microscope. Increased of 80 -‐and 10-‐fold accordingly
2. The establishment of reliable absolute ages of moraines [5, 7-‐9]. In order to receive reliable absolute age of moraines we have developed the method of radiocarbon dating of moraines with the use of autochthonous organic matter. In moraines we have found autochthonous glacio-‐chionophilous (special glacial) fine-‐ dispersed organics disseminated in fine-‐grained morainic material; its nature was identified and shown the possibilities for this organic usage for radiocarbon dating of moraines. It should be mentioned that the selection of samples by this method for radiocarbon dating of moraines is very effortful: in order to select own sample it is necessary to carry out excavation in moraine attaining several cubic meters. However, there are no alternatives for this method of moraines dating.
New starting positions in paleoglaciology and Quaternary Geology The correct genetic typing of moraines and pseudo-‐moraines and the method of reliable 14С dating of moraines together make the new starting positions in paleoglaciology and Quaternary Geology. Settled pattern regularities 1. The resulting facial-‐lithological data present strict correlative and paleoclimatic criteria [4, 6, 7]. It has been found that during the genetic transformation of moraine and pseudo-‐moraine deposits into alluvial/proluvial deposits, the oxide/protoxide ratio and clay content of the original deposits are well preserved. 2. In the Tien Shan, Pamir and Himalaya there was only one Pleistocene glaciation, and it took place in the Late Pleistocene epoch [4, 6]. There are three major stages in it. One must note that in the Tien-‐Shan and Pamir, the alluvial/proluvial deposits of the Early and Middle Pleistocene show extremely high values of oxide/protoxide ratio, i.e. they belong to the geochemical facies of ferric iron. The use of these criteria allowed to establish definitely that there was only one Pleistocene glaciation in the Tien-‐Shan and Pamir, and it occurred in the late Pleistocene. There are three main stages. 3. Morpho-‐litho-‐ and stratigraphically pattern regularity expressed in joining moraines and pseudomoraines.
Conceptual scheme of morpho-‐lithostratigraphic segmentation of generations of late Pleistocene and Holocene glaciations and massive delapsive gravitational formations in the Tien Shan. gl Ps I, gl Ps II and gl Ps III – late Pleistocene moraines of the 1st, 2nd, and 3rd generations, accordingly. gr – delapsive gravitational formations (pseudo-‐moraines). 1-‐ 7 – morphologically well-‐articulated Holocene moraines of the 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th, generations accordingly.
4. Morphologically expressed regularity disintegration of the Holocene glaciation [4, 5, 9]. On the example of the Tien-‐Shan, Pamir and the Himalayas we found out that Holocene glaciation disintegrates stadialy by the principle of dying oscillations. It distinguishes 7 main stages. The following radiocarbon dating were received for the first three stadial moraines of Holocene glaciations of one of moraine-‐glacial complex of the Tien-‐Shan: I stage– 8000 years, II stage – 5000 years, III stage– 3400 years. On the base of the received data we offered the scheme of stadial degradation of the Holocene glaciation in the mountains of Tien-‐Shan.
Morphologically apparent staged moraines (I -‐VII) in Tez-‐Ter moraine-‐glacial complex (Tien-‐ Shan).
Stadial (I-‐VI) generations of moraine -‐glacial complex; Stadial generations of the Holocene; moraine-‐glacial in the valley of Altyn-‐Dara River complex Duw Glacier (Himalayas). (Pamir). 7th stage is out of sight.
Schematic model of Tien-‐Shan glaciations degradation in the Holocene Horizontal axis – time scale (thousands of years) I, II, III, IV, V, VI, VII – glaciations stages related to morphologically expressed moraines of the Holocene moraine and glacial complexes. 8000, 5000, 3400 – radiocarbon age of stadial moraines, years; ? – estimated next stage of the Holocene glaciations This scheme may serve as a paleoglaciological basis for long-‐term forecasting of glacial and climatic changes of Central Asian mountain areas. The last shaft on this schematic model (located beyond zero age mark) is extrapolative by forecasting, taking into account really observed regularities. It represents the greatest interest in long-‐term forecasting of glacial and climate changes, as on its amplitude (future next splash of modern glaciation), starting time and duration will depend climate and glaciation in foreseeable future not only of the Tien-‐Shan, but the whole Central Asian region. The dating of the other stadial moraines – is a way to long-‐term forecast of glacial and climatic changes. For more detailed paleoglaciological reconstruction of the Holocene glaciation radiocarbon dating should be combined with isotope-‐oxygen (basing on ratio of isotopes 18О/16О) investigation of glaciers. However, a weak point of the isotope-‐oxygen studying of glaciers is definition of absolute age of ice cores. It is performed with the use of ratio-‐based models of age and depth of glacial thicknesses, constructed on the basis of characteristics of flow. The method of radiocarbon dating of moraines we offer allow to date the isotope-‐oxygen temperature curve of past received during drilling of mountain glaciers, that is to adhere it to reliable age scale [7, 8]. For this purpose, it is necessary to select series of samples on contacts of glacial ice and a superficial (ablative) moraine covering. Samples of ice will be used for isotope-‐oxygen analyses and samples of autochthonic organic substance from moraines will be used for radiocarbon dating. Conclusion Studies of paleo-‐glaciology and quaternary geology are closely connected. Due to incorrect genetic typing of moraines and pseudomorains and the lack of reliable absolute dating of moraines paleoglaciology and Quaternary geology now find themselves without reliable climate-‐stratigraphic benchmarks, which makes further research in this field hopeless. The situation should be viewed as a deadlock. That is why based on all of the above it can be concluded that: We must break the current impasse in paleo-‐glaciology and quaternary geology instead of waiting for decades when supposedly “quantity will be transformed into quality.” Today people need reliable long-‐term forecast of glaciation and climate, and this problem is getting more and more acute. The only way to overcome difficulties and get the necessary
result quickly enough is to start conducting paleo-‐glaciological reconstructions and geological study of quaternary period with the new starting positions (basing on quantitative facial lithologic indicators and reliable absolute dating). The answer to a question “What prevents from doing this” may be as follows: besides objective reasons, revealed in this report as well as our researches data (www.glaciology.ru, www.scorcher.ru/glaciology/index.php), subjective reasons – conservatism of scientists – take place. References 1. Bowen D, 1981. Quaternary Geology. «Mir», Moscow. 2. Shatravin VI, 1994a. Facial-‐lithological typification of main genetic generations of Quaternary deposits of high-‐mountain zones. In: Geology of the Cenozoic and seismotectonic of the Tien-‐Shan. «Ilim», Bishkek. 3-‐15. 3. Shatravin VI, 1994b. General regularities of glacial and gravitational types of lithogenesis of mountainous areas In: Geology of the Cenozoic and seismotectonic of the Tien-‐Shan. «Ilim», Bishkek. 15-‐26. 4. Shatravin VI, 2007a. Reconstruction of Pleistocene and Holocene glaciations in the Tien-‐ Shan from new starting positions. In: Climate, Glaciers and Lakes: Journey to the Past. “Ilim”, Bishkek. 26-‐46. 5. Shatravin VI, 2007b. Radiocarbon dating of moraines with the use of dispersed organics. In: Climate, Glaciers and Lakes: Journey to the Past. “Ilim”, Bishkek. 74-‐92. 6. Shatravin VI, Tuzova TV, 2010. New Starting Positions in Paleoglaciological Reconstructions at Long-‐Term Forecasting of Eurasia Glaciation and Climate. In: Collection of Scientific Papers No 65, dedicated to the memory of Academician Mirtckhlava C.E. Tbilisi. 240-‐244. 7. Shatravin VI, Tuzova TV, 2011a. Long-‐Term Forecast of Glaciation and Evaluation of Glacial Resources of Central Asia with Use of Isotopic Methods In: AASA Regional Workshop on “The Roles of Academies of Sciences in Water and Energy Problems in Central Asia and Ways for Their Solution», NAS KR, Bishkek. 85-‐90. 8. Shatravin VI, Tuzova TV, 2011b. Long-‐Term Forecast of Glaciation and Evaluation of Glacial Resources of Central Asia with Use of Isotopic Methods. Journal «Izvestiya of the National Academy of Sciences of the Kyrgyz Republic». Series of physics and technical, mathematical, mining-‐and-‐geological sciences. NAS KR, Bishkek 2(4): 24-‐27. 9. Shatravin VI, 2012. Establishment of regularity of disintegration of the Holocene glaciations through radiocarbon dating of dispersed organic matter from moraines. In: Andean-‐Asian Mountains Global Knowledge Exchange On Glaciers, Glacial Lakes, Water & Hazard Management. Field Expedition to Imja Glacial Lake. September 3-‐24. ICIMOD, Katmandu. 123-‐125.
Deep contradictions which have place in quaternary geology and paleoglaciology prevent from making a reliable long-term forecast. During INQ...
Published on Sep 25, 2013
Deep contradictions which have place in quaternary geology and paleoglaciology prevent from making a reliable long-term forecast. During INQ...