Features of shoreline displacement in the Holocene of Franz josef Land Archipelago
Abstract:Changes in the global sea level after the LGM caused the significant alteration in relation of land and sea in Arctic. The rise of the sea level in Arctic was accompanied with present tectonic processes. Marine terraces are formed with the combination of eustatic sea level fluctuations and glacioisostatic uplift of the territory with the significant role of complicated tectonic block movements. There are nearly about 150 radiocarbon ages data for Franz-Josef Land archipelago now. The represented conclusions are a generalization of the published data and results of our field researches with series of new radiocarbon dates.
We managed to collect valuable factual material during the Russian Arctic National Park expedition in 2012. The distinctions of post-glacial rise of different islands and peculiarities of Holocene deglaciation were identified with the help of marine terraces analysis.
The altitude of the terraces with the same age on different islands exceeds 15 meters in some cases. However, analysis of the data suggests that the continuous series of raised beaches from 35 m a.s.l. formed during the last 10000 years. It is impossible to build up an univocal model of emergence isobases with the existing data.
Alexandra Land Island was the special object of this investigation. The large beach ridge from Lunar Ice Cap to Kropotkina Ice Cap divides the island on two parts. The northern one is covered with marine sediments, whereas the southern – with glaciofluvial sediments with negligible areas of marine sediments. The difference between the terraces' ages of Alexandra Land on the Dezhneva Bay shore and the northern shore of island suggests that:
1) In the early Holocene the rate of the transgression exceeded the tectonic uplift of the territory;
2) Formation of the large central beach ridge occurred near 6700 years ago, the maximum marine limit in the Alexandra Land Island;
3) The rate of the tectonic rise of the territory exceeded the eustatic sea level rise in the period after 6700 years ago;
4) The formation of the large central beach ridge took place when the Ice Capes occupied less space than now.
We express our gratitude to the administration of Russian Arctic National Park for providing access to FJL archipelago and organization of the expedition.