Glaciology and Tectonics in the Aladaglar Mountains, Southern Turkey |
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Dr Attila Ciner, Haceteppe University, Ankara, joined us for two days during our visit to Cappadocia. On the first day, we were given insights into the volcanics of Cappadocia and on the second we travelled for about two hours to the Aladaglar Mountains (or White Mountains) in the south, with Attila, his wife Stephanie and son, to look at aspects of glaciology and tectonics.
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The location of the Aladaglar Mountains in southern
Turkey |
The Taurus range lies east/west in southern Turkey, forming part of the Alpine- Himalayan belt, associated with the closing of the Tethys Ocean and the collision of Africa, India and Eurasia in the Tertiary (<65Ma). The Aladaglar mountains (37°45’ N, 35°15’E) form part of the central Taurus range running from the southwest to the northeast for approximately 50 kilometres. They are between 25 and 30 kilometres wide, rising from 1100m to the region's highest peak, Demirkazìk (or Iron Peak) at 3756m. Today, there is a small glacier about 500m long on a north facing slope, major valleys on the eastern side, 3 or 4 smaller valleys on the west and the Yedigöller high plateau at 3200m with seven glacial lakes. It’s a very popular place for walking holidays!
Three geological events were important to the evolution of the region:
A stable continental margin formed during the Late Triassic – Early Cretaceous (~200-140 Ma) when platform carbonates were deposited in a shelf environment.
The distraction of continental margin during the Senonian (Late Cretaceous ~85.5-65 Ma) when the continental margin subsided due to block faulting, resulting in the first emplacement of ophiolites. The platform carbonate rocks and ophiolites were mixed forming ‘ophiolite melange’.
Napping of the continental shelf during the Maestrichtian (the youngest part of the Cretaceous). During this period, the Senonian basin was squeezed and compressional stress developed a napped structure (extremely folded or recumbent rock) within its basement. Several thrusts created huge nappes.
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The Aladaglar Range from the west near Camardi
(37°55’ N, 35°04’E) |
We looked at sites in a valley on the west of the range. The carbonate mountains were to the east, with an ophiolite nappe to the west and Miocene (~23-5Ma) fluvial deposits in bottom of the valley. A trans-tensional (strike-slip normal) fault at the base of the mountains ran parallel to valley and younger moraines. Whaleback forms (drumlins?), caves and deep gullies less than 10,000 years old up to 1 km deep were also evident on the sides of the mountains.
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Simplified structural unit diagram of the sites
visited |
In recent expeditions to the mountains, Attila recognised glacial landforms that had previously been mapped as alluvial deposits. As a result, all glacial deposits (mainly moraines and outwash deposits) in the area were mapped and samples were taken for cosmogenic (36Cl) dating. This relatively new technique is 10-15 years old and is based on detecting the atomic reaction between cosmic rays and minerals in rocks on the earth’s surface and the longer the exposure to rays the greater the reaction. Accuracy is +/-500 years so it is a very precise of method of dating but expensive at around $500 per sample.
In the field, large rocks were selected that were well rooted, as these were less likely to have moved or have been covered with snow. Samples of rock to 3 cm were chipped from the surface for analysis. 50 samples of glacial material were taken in the Aladaglar region and 30 were analysed giving no outlying results. The findings showed a gradual change in the age of the moraines from 9000 years at the bottom of the valley to 8000 years at the top. The dates were double checked by C14 dating deposits taken from a dry palaeo-lake on the east of the range. Importantly, glaciation 8-9000 years ago during the Holocene, which is considered a relatively warm period, was not part of the last glacial maximum, and is therefore difficult to explain, so current research is investigating climate change during the period further.
Field observations revealed that the ice cap once located in the Yedigöller high plateau (3200m) covered an area of 40 km2. It over-spilled as small to large glacial tongues into the surrounding valleys through the passes lying around 3500 m radiating northeast, west and east. Based on the smoothed bedrock surfaces, the peak elevation of the ice cap during its maximum extent is estimated to be around ca. 3600-4000 m with 300-400 m thick icecaps.
We stopped to investigate terminal moraines that appear as horseshoe shaped terraces on the sides of the mountains (see picture of terminal moraine below). Terminal moraines accumulate if a glacier stops for some time and the bigger the moraine the longer the ice stagnated. Also, the younger less eroded moraines have steeper the slopes (30°-40°) as they have been exposed to less erosion. At the site where we stopped, the ice advanced only as far as the ophiolite nappe but in the east the ice extended out 10km.
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A deep gully on the eastern flank of the Aladaglar
mountains |
The glacial till making up the moraine was found to be a non-sorted, non-stratified material ranging from clay to limestone boulders with a few erratics such as ophiolite and red radiolarite (a siliceous deep-sea sediment composed largely of the skeletons of radiolaria). Larger rocks were located at the brow of the moraine and there was also evidence of travertine deposits on top, as this mineral is formed from carbonate precipitated out of saturated glacial melts.
After looking at the moraines we checked out the fluvial deposits in the valley before going on to lunch. Deposits exposed next to the road suggest a flood plain with a young braided river. These consisted of poorly bedded layers of mudstone and conglomerate. The conglomerate being clast supported with rounded pebbles, none of which was limestone, indicating erosion from only the ophiolite side of the valley.
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A terminal moraine (with conifers) on the west
of the Aladaglar mountains |
We then made our way across the fault plane for a well-earned lunch at a fairly remote trout farm and restaurant in Pinharbus at the base of the mountain, but unfortunately it was closed for Ramadan! Attila used his charm and the restaurant owners drove several km to buy salad and bread whilst we further explored the fluvial environment, snacking on excellent apples that grow abundantly in the valley.
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Attila Ciner (in the trip T-shirt) enthusing
about fluvial deposits |
Lunch was washed down with Turkish beer at around 4:30 just giving us time to reach our hotel in Ürgüp in time for dinner.
Anne Martis
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Last modified on Wednesday, May 04, 2005 at 11:37
