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Land-Ocean Systems in the Siberian Arctic: Dynamics and History
eastern block reveals more complex ridge-to-basin structure and is composed of the Northwind
Basin and Northwind Ridge. A boundary between the blocks is marked by a chain of narrow
NE-SW and N-S trending echelon-like troughs, coinciding with the Nautilus Gap on the north.
The Northwind Basin contains a central horst-like block, surrounded by several narrow steepsided grabens. The eastward facing Northwind escarpment, marked by the sharpest gravity
gradient, represents the boundary between the Chukchi Borderland and Canada abyssal basin.
It is now broadly accepted that the Chukchi Borderland is underlain by thinned continental
crust, covered with the sediments of an uncertain age of less than 2 km thick on the uplifts and
more than 4 km thick within the troughs (Hall, 1990). As it was shown by Grantz et a!. (1993)
the Northwind Ridge is underlain by continental crust from a Cretaceous continental margin or
shelf basin.
The Mendeleev Ridge and Arlis Plateau appear in the gravity field as an unified block within
the 2000 m isobath. The gravity pattern suggests some similarity with De Long Uplift, while
both blocks are separated by the Toll' Rift.
The Chukchi Borderland and the Mendeleev Ridge are morphologically separated by Charlie
Gap, that links the Mendeleev and Chukchi abyssal plains. This feature is shown in the gravity
field by a linear minimum, that disintegrates into two orthogonal branches on the north and
merges on the south with sharp gravity low about -50 mGal over the Chukchi Abyssal Plain.
To compare this gravity pattern over the Charlie Gap with the similar ones over the other MCS
studied structures of the ERAM we suggest it is a manifestation of an extension structure called
Charlie Rift. A merger of this rift and the Toll' Rift in area of the Chukchi abyssal plain appears
to have led to significant crustal thinning and formation over this junction a deep subsided
Chukchi sedimentary basin. The latter, based on gravity data, might be filled with a
sedimentary succession not less than 8 to 9 km in thickness.
Summary
New geophysical, particularly MCS and satellite marine gravity data collected during the last
decade over the broad area of the ERAM provide a good basis for revision of the previous
hypotheses on the structure and tectonic genesis of the region. The data presented in this paper
allow us to suggest that the continental margin was strongly affected by the rifting process
which produced and is still creating rift systems and rift-related deeply subsided sedimentary
basins which are: the presently active Laptev Rift System, the inactive New Siberian Rift and
Vii 'kitskii Rift System in the East Siberian Sea, North Chukchi rift basin in the Chukchi Sea
and several rifts and rift basins in the area of the continental slope and adjacent marginal
plateaus (Toll' and Charlie rifts, Nautilus Trough, Chukchi and Northwind rift basins). The
older rifts and rift basins which are now abandoned may have commenced activity as early as
end of Jurassic to beginning of Cretaceous. The first episode of the oceanic related rifting
probably took place in the Chukchi Sector in response to initial breakup between North
American plate and North Alaska-Chukchi Block (Grantz et a!., 1990; Embry and Dixon,
1994). This event resulted in formation of the North Chukchi Basin and movement of the
Chukchi Borderland out of the Chukchi continental margin, as was suggested by Grantz et a!.
(1990). The East Siberia Basin may be a basin downwarped by the sedimentary load or an
analogue of the Sverdrup Basin in northern Canada (Sweeney et a!., 1990).
Next, in the Late Cretaceous to Early Tertiary time, the large extensional basins were formed
in East Siberian Sector. We speculate this event to be connected with a crustal dilatation/seafloor spreading in the Makarov Basin. It was also suggested by Grantz et a!. (1990) that this
"Laramide" (latest Cretaceous-earliest Tertiary) event created a system of the N-S trending
ridges and basins of the Chukchi Borderland and province of the listric-normal faults in the
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
eastern block reveals more complex ridge-to-basin structure and is composed of the Northwind
Basin and Northwind Ridge. A boundary between the blocks is marked by a chain of narrow
NE-SW and N-S trending echelon-like troughs, coinciding with the Nautilus Gap on the north.
The Northwind Basin contains a central horst-like block, surrounded by several narrow steepsided grabens. The eastward facing Northwind escarpment, marked by the sharpest gravity
gradient, represents the boundary between the Chukchi Borderland and Canada abyssal basin.
It is now broadly accepted that the Chukchi Borderland is underlain by thinned continental
crust, covered with the sediments of an uncertain age of less than 2 km thick on the uplifts and
more than 4 km thick within the troughs (Hall, 1990). As it was shown by Grantz et a!. (1993)
the Northwind Ridge is underlain by continental crust from a Cretaceous continental margin or
shelf basin.
The Mendeleev Ridge and Arlis Plateau appear in the gravity field as an unified block within
the 2000 m isobath. The gravity pattern suggests some similarity with De Long Uplift, while
both blocks are separated by the Toll' Rift.
The Chukchi Borderland and the Mendeleev Ridge are morphologically separated by Charlie
Gap, that links the Mendeleev and Chukchi abyssal plains. This feature is shown in the gravity
field by a linear minimum, that disintegrates into two orthogonal branches on the north and
merges on the south with sharp gravity low about -50 mGal over the Chukchi Abyssal Plain.
To compare this gravity pattern over the Charlie Gap with the similar ones over the other MCS
studied structures of the ERAM we suggest it is a manifestation of an extension structure called
Charlie Rift. A merger of this rift and the Toll' Rift in area of the Chukchi abyssal plain appears
to have led to significant crustal thinning and formation over this junction a deep subsided
Chukchi sedimentary basin. The latter, based on gravity data, might be filled with a
sedimentary succession not less than 8 to 9 km in thickness.
Summary
New geophysical, particularly MCS and satellite marine gravity data collected during the last
decade over the broad area of the ERAM provide a good basis for revision of the previous
hypotheses on the structure and tectonic genesis of the region. The data presented in this paper
allow us to suggest that the continental margin was strongly affected by the rifting process
which produced and is still creating rift systems and rift-related deeply subsided sedimentary
basins which are: the presently active Laptev Rift System, the inactive New Siberian Rift and
Vii 'kitskii Rift System in the East Siberian Sea, North Chukchi rift basin in the Chukchi Sea
and several rifts and rift basins in the area of the continental slope and adjacent marginal
plateaus (Toll' and Charlie rifts, Nautilus Trough, Chukchi and Northwind rift basins). The
older rifts and rift basins which are now abandoned may have commenced activity as early as
end of Jurassic to beginning of Cretaceous. The first episode of the oceanic related rifting
probably took place in the Chukchi Sector in response to initial breakup between North
American plate and North Alaska-Chukchi Block (Grantz et a!., 1990; Embry and Dixon,
1994). This event resulted in formation of the North Chukchi Basin and movement of the
Chukchi Borderland out of the Chukchi continental margin, as was suggested by Grantz et a!.
(1990). The East Siberia Basin may be a basin downwarped by the sedimentary load or an
analogue of the Sverdrup Basin in northern Canada (Sweeney et a!., 1990).
Next, in the Late Cretaceous to Early Tertiary time, the large extensional basins were formed
in East Siberian Sector. We speculate this event to be connected with a crustal dilatation/seafloor spreading in the Makarov Basin. It was also suggested by Grantz et a!. (1990) that this
"Laramide" (latest Cretaceous-earliest Tertiary) event created a system of the N-S trending
ridges and basins of the Chukchi Borderland and province of the listric-normal faults in the