Holocene Marine Terraces of Kunashiri Island, Kurile Islands

Geosciences, 2018

The integrated analysis of high-resolution multibeam bathymetry and single-channel seismic profiles around Salina Island allowed us to characterize the stratigraphic architecture of the insular shelf. The shelf is formed by a gently-sloping erosive surface carved on the volcanic bedrock, mostly covered by sediments organized in a suite of terraced bodies, i.e. submarine depositional terraces. Based on their position on the shelf, depth range of their edge and inner geometry, different orders of terraces can be distinguished. The shallowest terrace (near-shore terrace) is a sedimentary prograding wedge, whose formation can be associated to the downward transport of sediments from the surf zone and shoreface during stormy conditions. According to the range depth of the terrace edge (i.e., 10-25 m, compatible with the estimated present-day, local storm-wave base level in the central and western Mediterranean), the formation of this wedge can be attributed to the present-day highstand. By assuming a similar genesis for the deeper terraces, mid-shelf terraces having the edge at depths of 40-50 m and 70-80 m can be attributed to the late and early stages of the Post-LGM transgression, respectively. Finally, the deepest terrace (shelf-edge terrace) has the edge at depths of 130-160 m, being thus referable to the lowstand occurred at ca. 20 ka. Based on the variability of edge depth in the different sectors, we also show how lowstand terraces can be used to provide insights on the recent vertical movements that affected Salina edifice in the last 20 ka, highlighting more generally their possible use for neo-tectonic studies elsewhere. Moreover, being these terraces associated to different paleo-sea levels, they can be used to constrain the relative age of the different erosive stages affecting shallow-water sectors.

2 In sti tute of His tory and Ar chae ol ogy, Uni ver sity of Tartu, Lossi 3, 51003 Tartu, Es to nia 3 De part ment of Ge og ra phy, Uni ver sity of Tartu, Vanemuise 46, 51014 Tartu, Es to nia 4 Finn ish Mu seum of Nat u ral His tory, Uni ver sity of Hel sinki, Gustaf Hällströmin katu 2, 00014 Hel sinki, Fin land Rosentau A., Joeleht A., Plado J., Aunap R., Muru M. and Eskola K.O. (2013) De vel op ment of the Ho lo cene foredune plain in the Narva-Joesuu area, east ern Gulf of Fin land. Geo log i cal Quar terly, 57 (1): 89-100, doi: 10.7306/gq.1077

Palaeogeography, Palaeoclimatology, Palaeoecology, 1982

This paper deduces late Holocene eustatic sea-level changes from 14C dates and present elevations of almost all Holocene raised coral reefs in the Ryukyu Islands (an active island arc), without the assumption of a constant uplift rate. Stable relative sea levels are restored by using sea-level indicators, such as raised coral reef terraces, fossil coral, wave-cut notches, and beach rock. The oldest and the youngest 14C ages of calcium carbonate fossils, collected from a depositional terrace~urface, show their formative period. When all relative sea-level changes of thirteen islands are compared, the Ryukyu Islands form three groups according to the oldest age in the formative period of the Holocene raised reef terraces in each island, that is 6500 yr B.P., 5000 yr B.P., and 3500 yr B.P. The youngest of the terrace-formative periods in the three island groups correspond with each other. One eustasy explains the seismic upheaval and the formative process of the terrace~urfaces of the three island groups. The eustatic sea-level trend in the Ryukyu Islands can be summarized as follows. From 6500 to 3500 yr B.P., the sea level continued to rise generally. Around 6500 yr B.P., 5000 to 3500 yr B.P., and 3500 to 1700 yr B.P., the rates of sea-level rise became slower. The sea level between 3500 and 1700 yr B.P. was stable and it has been the highest in the Holocene. At that time its height was less than 1.0 m above the present sea level. The Holocene uplift rate of each island is estimated to be half to three times as great as that of the last 125 000 years. The uplift.rates of the three island groups in the late Holocene are inferred to have been decreasing exponentially. The crustal movement and the distribution of raised coral reefs are further discussed here.

Quaternary deposits of the lower reaches of Yenisei River serve as key sections for Russian sector of the Arctic, and some well-known formations (messovian, sanchugovian, kazanian, zyryanian, and karginian) were described here [Saks and Antonov, 1945; Saks, 1953]. Sanchugovskaya suite beds are characterized by dominantly clayey composition, depleted foraminifera complexes, accidental mollusk shells and spore and pollen spectra indicative of cold sedimentation environment. Kazanian beds are commonly clayey sand and sandy clay with abundant Boreal and Boreal-Arctic mollusk fauna and are also rich in microfauna. Karginian Formation, by Saks, includes an alluvium of river terraces, marine postglacial ingression deposits, lacustrine sediments, deluviual beds, and peat. Zyryanian deposits represent sandy and pebble beds as well as sandy clay with cobbles and pebbles. Troitsky [1966] based on the mollusk data argued a wide occurrence of karginian beds in the area. Then, in late 1960s, scientists of the Institute of Geology of the Arctic (Leningrad, USSR) suggested a new regional stratigraphy for the loose sedimentary cover of Yenisei River Mouth Region. By their scheme, all stratigraphic units there date back to Pliocene to Pleistocene and can be comprehended as results of three marine transgressions: Bolshehetskaya, Kochosskaya & Kazanian. Those sandy and clayey deposits interpreted earlier as zyryanian glacial were reconsidered as pre-Kazanian and included in the Ust'-Port beds . The Ust'-Port beds was defined by these authors as sand and silt layers bedded above the sanchugovian ones. In contrast to the latter, these are rich in foraminifera complexes. However, this standpoint implying the Neogene age for the most part of the sequence was then criticized in the literature . The concept of a widely-spread karginian unit was later revived based on the radiocarbon dating of voluminous organics . Kaplyanskaya and Tarnogradsky [1975] were inclined to consider the sanchugovain cobble sandy clay as a glacial product. New EPR , OSL and AMS [Astakhov and Mangerud, 2005] dates were yielded recently for Yenisei River Mouth Region. These dates support older (kazanian) age of the deposits recognized earlier as the Karginian Formation in the stratotypic sections at Cape Karginsky and in the Malaya Kheta river valley.

Baltica

The coastal slope morphology of the submarine coastal zone of the Eastern Gulf of Finland was identified during a VSEGEI survey (side–scan sonar profiling, echo sounding, surface sediment sampling). Along the northern coast of the Gulf, a subsurface of the sand terrace was mapped at the depths from 4-5 m (top) to 8-12 m (foot). In order to explain the morphogenesis of the terrace the development of coast over the Late Holocene was reconstructed using a mathematical model. It is suggested that tectonic processes (glacio–isostasy) were the main factors of the terrace forming at earlier stages; while at later stages sea–level changes have played the main role. The coastal development during the Late Holocene was subjected by the gradual erosion of the above–water terraces and the formation of underwater terraces. During transgressive phases the rate of coastal recession reached 0.5 m y-1, while at other times it was approximately half that. The submarine terrace, developed 3.2–1.2 kyr ...

Doklady Earth Sciences, 2010

Investigation of Pernatoe Lake sediments in the south of Paramushir Island has enabled us to obtain the first continuous pollen record of climate and vegetation changes in the north of the Kurile archi pelago during the Holocene. Series of radiocarbon datings of between 10 000 ± 40 and 2180 ± 40 years ago are evidence that the beginning of sediments accumulation, found after borehole development, is related to the Early Holocene. Diatom analysis has shown several stages in the lake development: raised bog on the border of the Pleistocene and Holocene, lagoon formation resulting from the sea level rise over 9-6 ky, and freshwa ter lake formation 6 ky and up to the present. Climate warming during the period attributed to the boreal and Atlantic periods of the Holocene is reflected by the dominance of Pinus pumila and Alnus serrulata assem blages in vegetation cover. Wide dune fields were formed in the Sea of Okhotsk and the Pacific shores of Para mushir Island 5-4 ky. Strengthening of atmogenic processes is related to cooling of the climate and drying of some areas of the underwater slope.

Boreas, 2004

The occurrence of sandy clay deposited in a warm marine environment just below the till of the last glaciation has created controversy about its age and stratigraphic position in the sedimentary basin of the Kola Peninsula. Data on marine microfauna, diatoms, malacofauna and pollen composition indicate that during the period when the sandy clay was deposited the climate was similar or even warmer than at present. According to 14 C dates, sedimentation of the sandy clay occurred around 40 ka BP. Based on these data, some researchers have attributed these marine deposits to the third Late Pleistocene Belomorian (sensu Lavrova 1960) interglacial transgression. At the same time there are geological indications suggesting re-deposition of these subtill sediments. To solve this problem we have reinvestigated the subtill interglacial marine deposits from the Varzuga section ($66.4°N and 36.6°E). Four different marine shell species and enclosing sandy clay sediments taken from the subtill marine unit of the section were dated by the electron spin resonance (ESR) and optically-stimulated luminescence (OSL) methods at about 103 and 104 ka, respectively. The results indicate that the subtill marine deposits belong to the first Late Pleistocene Boreal transgression that, according to our previous studies of the marginal areas of the Eurasian North, has occurred in the time interval from approximately 145 to 70 ka BP.

Journal of Paleolimnology, 2015

Diatom, rock magnetic, geochemical, and lithological studies of a sediment core from Paramushir Island (northern Kuril Archipelago) trace environmental shifts from bog to salt-water lagoon to freshwater lake over the past 10,000 14 C BP. Organic-rich mesic landscapes dominated the southern island until *8200 14 C BP. Transgression of the Sea of Okhotsk onto the island began sometime after 8200 14 C BP, resulting in the formation first of a salty (*8200-5700 14 C BP) then a brackish (*5700-5200 14 C BP) lagoon. With lowering of sea level after 5200 14 C BP, a freshwater lake formed, which has remained to the present day. This history parallels regional trends in the Russian Far East, where maximum sea levels occurred between *8000 and 4600 14 C BP, peaking at *6400 14 C BP. Sandy levels within the lake core suggest four intervals of aeolian activity (*4900-4800 14 C BP; 4300-3800 14 C BP; 3200-3000 14 C BP; 1900-900 14 C BP), perhaps related to drier than present climates. Palynological data indicate a dominance of Pinus pumila-Duschekia kamtschatica shrub tundra in the lowlands *8200-5800 14 C BP, marking the Holocene thermal maximum. This vegetation contrasts to modern, which established *5800 14 C BP and is a mix of coastal meadow, Betula-Salix low shrub tundra, and scattered Pinus and Duschekia thickets. The palynological record shows little response to mid-to-late Holocene climatic fluctuations except for a decrease in Pinus shrubs perhaps caused by changes in snow cover and/or summer temperature during the Little Ice Age.

Boreas, 2004

The occurrence of sandy clay deposited in a warm marine environment just below the till of the last glaciation has created controversy about its age and stratigraphic position in the sedimentary basin of the Kola Peninsula. Data on marine microfauna, diatoms, malacofauna and pollen composition indicate that during the period when the sandy clay was deposited the climate was similar or even warmer than at present. According to 14 C dates, sedimentation of the sandy clay occurred around 40 ka BP. Based on these data, some researchers have attributed these marine deposits to the third Late Pleistocene Belomorian (sensu Lavrova 1960) interglacial transgression. At the same time there are geological indications suggesting re-deposition of these subtill sediments. To solve this problem we have reinvestigated the subtill interglacial marine deposits from the Varzuga section ($66.4°N and 36.6°E). Four different marine shell species and enclosing sandy clay sediments taken from the subtill marine unit of the section were dated by the electron spin resonance (ESR) and optically-stimulated luminescence (OSL) methods at about 103 and 104 ka, respectively. The results indicate that the subtill marine deposits belong to the first Late Pleistocene Boreal transgression that, according to our previous studies of the marginal areas of the Eurasian North, has occurred in the time interval from approximately 145 to 70 ka BP.

The Holocene, 2002

A HOLOCENE RESEARCH PAPER Abstract: The study of Holocene deposits on Iturup Island is very important for understanding palaeolandscape changes on the island. It is separated by deep straits from the neighbouring islands and was isolated during the last glacial maximum. Landscape changes over the last 40000 years and the role of refugia on vegetation development are discussed. Changes in natural processes in this region were controlled both by global climatic changes and by regional factors. Birch forests developed at the warming about 36-37 ka ago, whereas tundrapark landscape developed with the cooling of the last glacial maximum. Holocene environments reflect climatic changes and sea-level oscillations. The fluctuation of warm and cold currents influenced the landscape development. At the Holocene Optimum (about 6 ka) broadleaved forests with Quercus, Phellodendron, Carpinus, Juglans, Fagus, Fraxinus and Syinga occupied the Okhotsk side of central Iturup. Climate was warmer than present and the sum of active temperatures (Vt >-10'C) was not less than 1 800TC. The warming was coincident with the transgression with the highest sea level up to 3.5 m above present sea level (PSL). Numerous coastal lakes were formed at this time. A shallow strait occurred on the low Vetrovoy isthmus. The sea-level drop at 4700-4500 radiocarbon years BP led to the development of large dunefields only within bays with a flat coast due to the supply of sandy material from the inshore drainage zone. At the beginning of the late Holocene about 4000 BP the vegetation changed very little due to the warm current influence. Cool-temperate forests with dominant Quercus had a wide distribution, but the diversity of broadleaved genera decreased. A minor transgression occurred about 4100-4000 BP with a sea-level rise on about 2.5 m above PSL. Active accumulation of deposits tookplace in the coastal zone at this time. Great vegetation changes and climatic deterioration took place in the last 2000 years BP. Cool-temperate broadleaved forests were confined to the Okhotsk side of the central island. Grasslands and swamps also developed in the coastal lowlands at this time. A minor regression led to the formation of large dunefields. Isthmuses increased and coastal wetlands with lakes formed. The presence of marine diatoms in floodplain lake deposits indicates a sea-level rise at about 1060 ± 60 BP. At this time warming was not intensive, but was well pronounced. The last phase of active aeolian accumulation took place during the 'Little Ice Age' cooling and regression.