Lunar and Planetary Science XXXVII (2006) 1065.pdf THE AZAS PLATEAU IN SOUTHERN SIBERIA: A PROPOSED TERRESTRIAL ANALOGUE SITE FOR ICE-MAGMA-FLOOD PROCESSES ON MARS. G. Komatsu1, G. G. Ori1, S. G. Arzhannikov2 and A. V. Arzhannikova2, 1International Research School of Planetary Sciences, Università "G. d'Annunzio", Viale Pindaro 42, 65127 Pescara, Italy; 2The Institute of the Earth's Crust Russian Academy of Sciences, Siberian Branch Lermontova 128, 664033 Irkutsk Russia. Introduction: Recent Mars missions have opened using the K-Ar dating technique [9, 10]. These two a new level of geological investigation on the red studies have a wide range of discrepancies for the age planet. And more than ever understanding of estimates. But it is reasonable to state that the Azas processes, in particular of ice-magma inactions and lava plateau began to form during the Late Pliocene related flooding, is becoming crucial [e.g., 1, 2]. and its volcanism continued during the Pleistocene. Terrestrial analog studies have been proven to be Past studies of the Azas Plateau have focused useful in providing insights on such processes. In the mostly on geochemistry and chronology of the past, Iceland has been the most studied and volcanics. We are conducing primarily referenced as a terrestrial analog site for ice-magma geomorphological investigation of various landforms in the Azas Plateau in order to understand physical interactions [e.g., 3] but examples of such processes processes responsible for the creation of them. The can be found also in Antarctica [e.g., 4] and in results of the geomorphological investigation will be Canada [e.g., 5]. assessed together with geochemical and The Azas Plateau is a relatively unknown chronological information in order to further deepen volcanic field in southern Siberia. But it is a part of our knowledge of history of the Azas Plateau. the Mongolian plateau that has been compared with the Tharsis bulge on Mars in terms of diverse Glaciation: The Sayan mountains and Azas processes operated on large-scale tectonomagmatic Plateau experienced intense glaciation in the complexes [6]. This volcanic field potentially Quaternary. The maximum extent of the ice sheet provides rich information on ice-magma interactions. during the late Quaternary period is considered to be And we propose this area as a terrestrial analogue site rather extensive [11], covering the majority of the for future studies. Azas Plateau. But the coverage probably changed depending on the period. For example, the large ice sheet appears to have shrunk and during the last ice age glaciers were probably confined in valleys. In the Azas Plateau today, most of glaciers have disappeared. However a wide variety of glacial morphology exist, including U-shaped valleys, cirques, moraines, and erratics (Fig. 2). Figure 1. Location map of the Azas Plateau. Azas Plateau: The Tuva volcanic province is located in southern Siberia and the largest lava field in the province is the Azas Plateau volcanic field. The Azas Plateau is a part of the east Tuva highland that is bordering the Todza Basin to the west (Fig. 1). Figure 2. Glaciated mountain range in the Azas Both are situated in the Tuva Republic of the Russian Plateau. Federation. The Cenozoic Azas Plateau volcanic field covers over 2000 km2 and the volume of volcanics is estimated to be as much as 600 km3 [7]. The compositions of the Azas Plateau volcanics are trachybasalt and basanite [8]. The chronology of eruptions in the Tuva volcanic province is studied Lunar and Planetary Science XXXVII (2006) 1065.pdf Tuya edifices: Sub-ice eruptions of lavas melt the Jökulhlaup occurrence: Outburst of glacier ice above and often form edifices called tuya within meltwater is a common occurrence in Iceland. For the meltwater englacial lakes, but eruptions in open example, a wide range of geomorphology resulted lakes (perhaps ice-dammed on some sides) may have from such cataclysmic floods are observed [e.g., 13]. also happened. There are close to 10 tuya edifices of We are currently investigating the possibility of various sizes and ages distributed in the area (Fig. 3) past Jökulhlaup occurrence in the Azas Plateau. And [8, 12]. there are indications of such processes, including scablands and streamlined-hills. Diverse modes of flood landform creation are envisaged in the Azas Plateau. Some may require eruption of lavas as a triggering mechanism but others may not. Conclusions: The Azas Plateau in southern Siberia is rich in examples of landforms that resulted from glaciation and ice-magma interactions. These landforms are currently under investigation in order to know what physical factors control their formation. Understanding these processes in this Figure 3. An example of tuya. Sorug-Chushku-Uzu, plateau will deepen our knowledge that would be Azas Plateau. applicable to studies of similar processes on Mars. Access is a problem, but it is easier than to reach The volcanic field hosts also non sub-ice Mars. volcanoes. Therefore a comparison would be possible between sub-ice and non sub-ice volcanoes of similar References: [1] Chapman, M. G. and Tanaka, K. chemical compositions to see how the presence of ice L. (2002) Icarus, 155, 324–339. [2] Rodriguez et al. could affect morphology of the edifices. (2005) Icarus, 175, 36–57. [3] Volcano/ice The tuya edifices on the Azas Plateau are Interaction Workshop (2000) Abstract volume, Pleistocene in age and their formation coincided with Reykjavík, Iceland. [4] Smellie, J. L. and Skilling, I. extensive glaciation of different ages in the region. P. (1994) Sedimentary Geology, 91, 115–129. [5] The wide-spanned ages of tuyas provide an Hickson, C. J. (2000) Geomorphology, 32, 239–261. opportunity to assess the effects of degradational [6] Komatsu et al. (2004) Geology, 32, 325–328. [7] processes such as glaciation, slope failures, and Yarmolyuk et al. (1999) Transactions (Doklady) of fluvial dissection. the Russian Academy of Sciences/Earth Science The most characteristic lithology of sub-ice Section, 368, 907–911 (in Russian). [8] Litasov, Y. eruption is hyaloclastite (Fig. 4). This lithology is D. et al. (2001) Northeast Asian Studies, 6, 201–226. commonly observed with tuyas and they provide [9] Rasskazov et al. (2000) Geochronology and geodynamics in the Late Cenozoic: (South Siberia - various important information on the environment in South and East Asia). Nauka, Novosibirsk, 228 pp. which the tuyas were forming. (in Russian). [10] Yarmolyuk et al. (2001) Vulkanologiya I Seismologia (Volcanology and Seismology), 3, 3–32 (in Russian). [11] Grosswald, M. G. (1965) Topographic formation of the Sayano- Tuvinsky upland. Nauka, Moscow, 166 pp. (in Russian). [12] Komatsu et al. (2004) PSS, 52,167–187. [13] Carrivick et al. (2004) Geomorphology, 63, 81–102. Figure 4. Hyaloclastite. At Shivit-Taiga, Azas Plateau..