Bolshiyarwv and Molodkov: Marine Pleistocene Deposits ofthe Taymvr Peninsula
473
frequency of these coarse clasts does not exceed 5-10% by volume of the embedding
sediments. The occurrence of coarse clasts has been taken as an argument for interpreting these
sediments as being of glacial origin (Urvancev, 1931; Troitskii,1966; Kind and Leonov,1982,
Zolnikov and Shevko, 1989). However, in all studied outcrops it was found that the sediments
are clearly laminated. The lower unit sediment often contained a considerable amount of ice, in
particular ice wedges and ice bodies of unknown origin up to 60 m in thickness.
The sediments are usually poor in fossils, sometimes totally barren. However, some fossils,
though rarely observed, can be found in the upper part of the lower unit sediments, e.g. the
marine mollusc Portlandia arctica, foraminifers of the genus Hynesina sp., freshwater and
estuary species of diatoms (A.unotia diodon, Eunotia pracrupta, Tabellaria jenestrata,
Pinnularia sp, Cyclotella striata, Stephanodiscus astrea), and marine species of diatoms
(Paralia sulcata). Most diatoms were redeposited from Cenozoic sediments. The
palaeoenvironmental indications point towards cold and freshwater basins. The transition from
more massive clayey silts to varved clays also indicates that brackish basins were replaced by
freshwater basins. The pelecypod fauna of the lowermost part of the lower sedimentary unit is
boreal in composition, indicating warmer sea conditions. The lower sedimentary unit consists
of not only clay and silt but of more coarse deposits too. The roof of the lower unit lies at an
altitude of 160 to -30 m a.m.s.l. and its relief is very contrasting (Figure 2).
The upper sedimentary unit is present mostly as erosional remnants of a marine deposit that
once covered significant parts of the TaymyrTaimyr Peninsula. These deposits have often been
considered glacial in origin due to their sharp morphology and sandy to gravely composition
(Kind and Leonov, 1982). However, the internal structure of these deposits, although rarely
exposed due to a lack of recent erosion and active slope processes, indicates a coastal deltaic
facies of these sediments. Molluscs (Hiatella arctica, Astarte borealis, Mya truncata),
foraminifera (Haynes ina orbicularis, Retroelphidium ex gr. clavatum, Cribroelphidium
granatum, Astrononion gallowayi, Bucella jrigida, Cassidulina neoteretis) and diatom
(Navicula placentula, N. radiosa, Stephanodiscus astrea, Tabellaria jenestrata, Pinullaria
borealis, Cocconeis disculus, Amphora ovalis var lybica, Cyclotella kuetzingiana var.
schumannnii, Caloneis bacillum) assemblages, found in some sections belonging to this upper
sedimentary unit, indicate a delta-marine, coastal-marine, cold and brackish sedimentary
environment. The altitude of bedding of upper unit is from -45 to 175 m a.m.s.l. The most
widespread level of marine terraces consisting of sand and pebbles of the upper unit sediments
is at 100 m a.m.s.l. in the central part of Taymyr.
Discussion and conclusions
The deposits can be divided into a number of groups on the basis of their composition and their
age, as detennined by ESR dating:
1) sandy-gravely erosional remnants with a scattered distribution. Dating falls within a time
frame of 70 to 100 ka BP.
2) Clayey silts of a deep-water facies of marine sediments of the same age - 86 ka BP.
3) Clayey silts aged between 116 and 140 ka BP.
4) Clayey silts aged between 235 and 268 ka
5) Sand of shallow-water marine facies aged 289 ka BP.
6) Sandy silts aged between 316 and 336 ka BP.
7) Sand and gravels aged 535 ka BP.
This is a first attempt to date marine Quaternary deposits of the Taymyr Peninsula. We did not
have an opportunity to date all geomorphological levels. However, the bedding of studied
sediments at very different altitudes suggests that their modern position is under the influence of
473
frequency of these coarse clasts does not exceed 5-10% by volume of the embedding
sediments. The occurrence of coarse clasts has been taken as an argument for interpreting these
sediments as being of glacial origin (Urvancev, 1931; Troitskii,1966; Kind and Leonov,1982,
Zolnikov and Shevko, 1989). However, in all studied outcrops it was found that the sediments
are clearly laminated. The lower unit sediment often contained a considerable amount of ice, in
particular ice wedges and ice bodies of unknown origin up to 60 m in thickness.
The sediments are usually poor in fossils, sometimes totally barren. However, some fossils,
though rarely observed, can be found in the upper part of the lower unit sediments, e.g. the
marine mollusc Portlandia arctica, foraminifers of the genus Hynesina sp., freshwater and
estuary species of diatoms (A.unotia diodon, Eunotia pracrupta, Tabellaria jenestrata,
Pinnularia sp, Cyclotella striata, Stephanodiscus astrea), and marine species of diatoms
(Paralia sulcata). Most diatoms were redeposited from Cenozoic sediments. The
palaeoenvironmental indications point towards cold and freshwater basins. The transition from
more massive clayey silts to varved clays also indicates that brackish basins were replaced by
freshwater basins. The pelecypod fauna of the lowermost part of the lower sedimentary unit is
boreal in composition, indicating warmer sea conditions. The lower sedimentary unit consists
of not only clay and silt but of more coarse deposits too. The roof of the lower unit lies at an
altitude of 160 to -30 m a.m.s.l. and its relief is very contrasting (Figure 2).
The upper sedimentary unit is present mostly as erosional remnants of a marine deposit that
once covered significant parts of the TaymyrTaimyr Peninsula. These deposits have often been
considered glacial in origin due to their sharp morphology and sandy to gravely composition
(Kind and Leonov, 1982). However, the internal structure of these deposits, although rarely
exposed due to a lack of recent erosion and active slope processes, indicates a coastal deltaic
facies of these sediments. Molluscs (Hiatella arctica, Astarte borealis, Mya truncata),
foraminifera (Haynes ina orbicularis, Retroelphidium ex gr. clavatum, Cribroelphidium
granatum, Astrononion gallowayi, Bucella jrigida, Cassidulina neoteretis) and diatom
(Navicula placentula, N. radiosa, Stephanodiscus astrea, Tabellaria jenestrata, Pinullaria
borealis, Cocconeis disculus, Amphora ovalis var lybica, Cyclotella kuetzingiana var.
schumannnii, Caloneis bacillum) assemblages, found in some sections belonging to this upper
sedimentary unit, indicate a delta-marine, coastal-marine, cold and brackish sedimentary
environment. The altitude of bedding of upper unit is from -45 to 175 m a.m.s.l. The most
widespread level of marine terraces consisting of sand and pebbles of the upper unit sediments
is at 100 m a.m.s.l. in the central part of Taymyr.
Discussion and conclusions
The deposits can be divided into a number of groups on the basis of their composition and their
age, as detennined by ESR dating:
1) sandy-gravely erosional remnants with a scattered distribution. Dating falls within a time
frame of 70 to 100 ka BP.
2) Clayey silts of a deep-water facies of marine sediments of the same age - 86 ka BP.
3) Clayey silts aged between 116 and 140 ka BP.
4) Clayey silts aged between 235 and 268 ka
5) Sand of shallow-water marine facies aged 289 ka BP.
6) Sandy silts aged between 316 and 336 ka BP.
7) Sand and gravels aged 535 ka BP.
This is a first attempt to date marine Quaternary deposits of the Taymyr Peninsula. We did not
have an opportunity to date all geomorphological levels. However, the bedding of studied
sediments at very different altitudes suggests that their modern position is under the influence of