Available online at www.sciencedirect.com
ScienceDirect
Russian Geology and Geophysics 57 (2016) 1283–1287
www.elsevier.com/locate/rgg
Sediments in the Gakkel Ridge rift zone (Arctic Ocean):
structure and history
P.V. Rekant a,b,*, E.A. Gusev a
a
I.S. Gramberg All-Russian Research Institute of Geology and Mineral Resources of the World Ocean,
Angliiskii pr. 1, Saint Petersburg, 191120, Russia
b
A.P. Karpinsky All-Russian Research Geological Institute, Srednii pr. 74, Saint Petersburg, 199106, Russia
Received 3 August 2015; accepted 28 August 2015
Abstract
The available seismic and magnetic data show the Gakkel Ridge rift zone consisting of the Atlantic and Siberian segments divided by a
tectonic suture at 70º E. The two segments have had different histories recorded in their sedimentary cover. Apart from the difference in its
morphology, the Siberian segment differs from the Atlantic one in the existence of a series of deposition centers, which might represent a
vast Paleogenic basin that formed prior to the Gakkel Ridge. The simple model of North Atlantic spreading fails to explain the long and
complex history of the Gakkel Ridge rift and the existence of the depocenters. The particular structure of this zone might have resulted from
the growth of rift mountains by accretion of magmatic material during the Paleogene, without significant sea floor spreading.
© 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
Keywords: rift zone; sediments; Eurasian Basin; Arctic Ocean; Gakkel Ridge
Introduction
Sediments in geological structures bear record of significant
events in their history. The sedimentary structure of the Gakkel
Ridge rift zone, studied jointly by geological and geophysical
methods, can provide insights into the evolution of the ridge
and its surrounding basins.
Early synthesis of the structure and history of the Eurasian
Basin of the Arctic Ocean was based mainly on aeromagnetic
and gravity surveys with sparse seismic data (Demenitskaya
and Kiselev, 1968; Kiselev, 1986; Sweeney et al., 1982; Vogt
et al., 1979). A series of linear magnetic anomalies (LMA)
identified in the Nansen and Amundsen Basins and correlated
with those in North Atlantic (Glebovsky et al., 2006; Karasik,
1968; Vogt et al., 1979) were interpreted in terms of spreading
in the Gakkel Ridge and its links with both the global system
of midocean ridges and with the Moma rift system (Gramberg
et al., 1990). The Gakkel Ridge was hypothesized to be the
youngest Cenozoic endmember of the system (Karasik et al.,
1983; Naryshkin, 1987; etc.). Its history has been explained
by a universally accepted spreading model, which however
fails to allow for the very thin crust in the rift zone, ultraslow
spreading rates, and a large depth of the rift valley, the features
* Corresponding author.
E-mail address: [email protected] (P.V. Rekant)
reported soon after which differ it from other mid-ocean
ridges.
This study focuses on the Gakkel Ridge rift zone, which
comprises the rift valley itself and its flanking mountains up
to LMA 5. We discuss features in the regional sedimentary
structure revealed by seismic reflection profiling, which call
for revision of some essential points in the existing models.
Results
According to the available bathymetric (Jakobsson et al.,
2012), magnetic (Gaina et al., 2011), gravity, and seismic data
(Glumov, 2012), the Gakkel Ridge can be divided into the
Atlantic and Siberian segments (Fig. 1) along ~70° E, the line
corresponding to a kink of major regional structures. In
this respect, of special interest are two seismic profiles
AWI20010300 and AWI20010100 (Jokat and Micksch, 2004)
acquired across the Gakkel Ridge rift within its Atlantic and
Siberian segments, respectivetely (Fig. 2). The two profiles
show, respectively, thin sediments along the ridge axis within
Atlantic segment and more than kilometer-thick sedimentary
fill of the rift valley in the Siberian one.
The Atlantic segment looks like a spreading Atlantic
mid-ocean ridge, with a prominent linear rift valley (Fig. 1)
with a relative height in the basement topography of 3500 m
(Naryshkin, 1987). The valley has steep sides composed of
igneous rocks (Fig. 2a), judging by large amounts of basalt,
1068-7971/$ - see front matter D 201 6, V.S. So bolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.rgg.201
+
6.08.013
1284
P.V. Rekant and E.A. Gusev / Russian Geology and Geophysics 57 (2016) 1283–1287
Fig. 1. Bathymetry of the Eurasian Basin in the Arctic Ocean (Jakobsson et al., 2012) (a) and a fragment of a magnetic anomaly map (Gaina et al., 2011) (b), with
LMA locations according to (Chernykh and Krylov, 2011). White dash line divides Gakkel Ridge into the Atlantic (AS) and Siberian (SS) segments.
gabbro-dolerite, and peridotite clasts recovered by dragging
(Michael et al., 2003). Magnetic anomalies are distinct
lineations (Fig. 1): LMA from 2 to 24 (Chernykh and Krylov,
2011; Vogt et al., 1979).
The Siberian segment differs in rift morphology, magnetic
and gravity patterns, as well as in the sedimentary structure.
The rift valley has a less prominent expression in seafloor
topography (Fig. 1 and 2b) due to the presence of thick
sediments (see below). The relative height within the rift
valley is reduced to 700–900 m on average, rarely reaching
1500 m (Michael et al., 2003), with the greatest contrasts in
the mountains flanking the rift valley and smaller difference
toward the basin centrocline. It is difficult to trace LMA along
the ridge from the Atlantic segment, because of an orthogonal
blind zone at the boundary between the two segments.
Therefore, many anomalies are fragmentary while reliably
identified LMA are fewer in the Siberian segment than in the
Atlantic one (Fig. 1).
Finally, there are several local deposition centers with 0.5
to 3–4 km thick sediments (Figs. 2b, 3). Depocenters (Fig. 3)
were first revealed in seismic profiles near the Laptev Sea
continental margin in the centroclinal part of the Eurasian
Basin (Gusev et al., 2002; Sekretov, 2002). The large sediment
thickness reaching 4 km in the rift valley was explained by
ultraslow spreading and voluminous clastic input from the
Laptev Sea shelf. However, another depocenter with ~1500 m
thick sediments was discovered soon (Jokat and Micksch,
2004) in the Eurasian Basin center (at 86° N; 73° E) far from
the existing source areas (Figs. 2b, 3).
Similar depocenters with quite a thick sediment fill (Fig. 3)
appear in the immediate vicinities of the rift valley in all ten
seismic profiles collected across the Amundsen Basin within
the Siberian segment during the Shelf-2011 trip (Glumov,
P.V. Rekant and E.A. Gusev / Russian Geology and Geophysics 57 (2016) 1283–1287
1285
Fig. 2. Fragments of AWI20010100 (a) and AWI20010300 (b) seismic profiles (Jokat and Micksch, 2004) that cross the Gakkel rift valley in the Atlantic and Siberian
segments, respectively (see panel (c) for their location). LMA locations are according to Glebovsky et al. (2006).
2012). Unfortunately, only one profile ran across the entire
rift valley while the others stopped 30–50 km away, in the
flanking mountains next to the LMA 5–6.
Thus, the available seismic data from the Siberian segment
of the Gakkel Ridge (Fig. 2) show multiple deep compensated
basins to 2–3 km thick. Westward from the LMA 15–16, the
extensive east Amundsen basin gives way to local basement
uplifts alternated with prominent depocenters (Fig. 2b) traceable all along seismic lines up to the LMA 5 and quite possibly
as far as the rift valley (Fig. 3) (Rekant et al., 2015).
The existence of the system of deep compensated basins
upon a basement with its paleomagnetic age younger than
10 Ma (Glebovsky et al., 2006 Vogt et al., 1979), requires
thoughful explanation.
(1) The area is located more than 300–400 km far from the
nearest clastic sources and is a zone of very slow hemipelagic
deposition. (2) The sea floor in the Amundsen Basin part next
to the Gakkel Ridge is flat (a dip of 0.0002), which precludes
high-energy turbidite flows which would transport large
amounts of clastic material from the Barents–Kara shelf. (3)
Furthermore, no branching system of active submarine canyons required for the operation of such a hypothetical system
appears in the available bathymetric data. (4) Gravity sediment
redeposition recorded in central Amundsen basin (Svindland
and Vorren, 2002) may result from local erosion of seamounts
and leads only to redistribution of sediments. (5) Clastic
transport of Barents and Kara terrigenous sediments into the
Amundsen Basin passing by the deposition traps in the Gakkel
Ridge is still less probable.
Extrapolation of ACEX-302 data retrieved from the Lomonosov Ridge (Backman et al., 2008) onto the Amundsen
Basin imaged by seismic data (Chernykh and Krylov, 2011;
Rekant et al., 2015; Weigelt et al., 2014) indicates that the
fastest sedimentation rates in the Arctic Ocean can reach
290 m/Myr. However, they are restricted to Cretaceous sediments in narrow local grabens transported from nearby
orogens during tectonic activity. As tectonic activity decays
and the basin broadens, the deposition decelerates to 111–
38.5 m/Myr in Cenozoic nearshore and neritic facies. Hemipelagic deposition for the past 20 Myr has been, according to
different estimates, as slow as <12.6 m/Myr (Chernykh and
Krylov, 2011) or 14 to 23 m/Myr (Backmann et al., 2008).
The theoretical sediment thicknesses at different distances
from the rift valley can be estimated using these rates, with
reference to the Eurasian Basin opening model: they should
not exceed 40 m in the rift valley with a paleomagnetic age
of the basement younger than 2 Ma and 200 m in the rift
mountains (zone of LMA 1-4). These results are consistent
with borehole data from the Lomonosov Ridge (Backman et
al., 2008) where Upper Miocene–Pliocene (lithological subunit
1/3) and Quaternary (lithological subunit 1/2) sediments are
about 120 and 20 m thick, respectively.
1286
P.V. Rekant and E.A. Gusev / Russian Geology and Geophysics 57 (2016) 1283–1287
Fig. 3. Locations of depocenters on the Shelf-2011 seismic lines fragments (A11-010 through A11-034) (Gusev et al., 2002; Glumov, 2012; Secretov, 2002). Symbols:
1, water; 2, unconsolidated sediments; 3, acoustic basement; 4, location of LMA 5; 5, Gakkel Ridge rift valley; 6, local depocenter and its sediment thickness. Dash
line divides Gakkel Ridge into the Atlantic (AS) and Siberian (SS) segments.
P.V. Rekant and E.A. Gusev / Russian Geology and Geophysics 57 (2016) 1283–1287
However, seismic data (Glumov, 2012; Gusev et al., 2002;
Jokat and Micksch, 2004; Sekretov, 2002) reveal a large
number of local depocenters of >1 km sediment thicknesses
within rift mountains: two depocenters in the rift valley and
eight in its immediate vicinity (Fig. 3). The same pattern may
exist elsewhere along the ridge, judging from its general
sedimentary structure.
The seismic and modeling data can be reconciled assuming
either 10 to 100 times faster hemipelagic deposition (up to
100–150 m/Myr), or older ages of the depocenters. Thick
Pliocene–Quaternary sediments do exist in the Arctic Ocean
but they rather form a prograding continental slope wedge
thinning rapidly toward the ocean (McNeil et al., 2001). For
instance, the thickness of the synoceanic Miocene–Quaternary
sediments in the Podvodnikov Basin varies within a small
range from 300 to 500 m thick, which indicates a relatively
small difference in deposition rates between the basin center
and its sides (17 m/Myr against 27 m/Myr, respectively). It
becomes clear that the sedimentation rates of the order of
100–150 m/Myr in the central Eurasian Basin appears hardly
possible given the extremely low terrigenous sediment influx.
Therefore, Paleogene rather than Miocene–Pliocene ages of
the local depocenters appear to be the only reasonable
explanation for their existence within the rift mountains and
in the rift valley. This make us to assume a Paleogene
(Eocene (?)) age of the rift zone in the Siberian segment of
the Gakkel Ridge.
Conclusions
The reported data lead to the following inferences.
1. The Gakkel Ridge consists of the Atlantic and Siberian
segments divided by a tectonic suture at 70º E. The two
segments had different recent histories recorded in their
sedimentary structure. The division is expressed in the morphology and structure of magnetic anomalies.
2. Unlike the Atlantic segment, the Siberian rift segment
is filled with thick sediments and encloses a large number of
Cenozoic deposition centers. The depocenters might represent
a vast Paleogene basin, which existed in the place of the
present-day Gakkel Ridge.
3. The simple model of North Atlantic spreading fails to
explain the long and complex history of the Gakkel Ridge rift
and the existence of depocenters with thick sediments. The
particular structure of this zone might have resulted from the
growth of rift mountains by accretion of magmatic material
during Paleogene time, without significant sea floor spreading.
References
Backman, J., Jakobsson, M., Frank, M., Sangiorgi, F., Brinkhuis, H.,
Stickley, C., O’Regan, M., Løvlie, R., Pälike, H., Spofforth, D., Gattacecca, J., Moran, K., King, J., Heil, Ch., 2008. Age model and
core-seismic integration for the Cenozoic Arctic Coring Expedition
sediments from the Lomonosov Ridge. Paleoceanography 23 (1), PA1S03.
Chernykh, A.A., Krylov, A.A., 2011. Sedimentogenesis in the Amundsen
Basin from geophysical data and drilling results in the Lomonosov Ridge.
Dokl. Earth Sci. 440 (2), 1372–1376.
1287
Demenitskaya, R.M., Kiselev, Yu.G., 1968. Seismic constraints on structure,
morphology, and sediments in the central Lomonosov Ridge, in: Geophysical Surveys in the Arctic [in Russian]. NIIGA, Leningrad, Issue 5,
pp. 33–46.
Gaina, C., Werner, S., Saltus, R., Maus, S., 2011. Circum-Arctic mapping
project: new magnetic and gravity anomaly maps of the Arctic. Geol. Soc.
London Memoirs 35, 39–48.
Glebovsky, V.Yu., Kaminsky, V.D., Minakov, A.N., Merkur’ev, S.A.,
Childers, V.A., Brozena, J.M., 2006. Formation of the Eurasia basin in
the Arctic ocean as inferred from geohistorical analysis of the anomalous
magnetic field. Geotectonics 40 (4), 263–281.
Glumov, I., 2012. Expedition “Arctic-2011” for determination limit of the
continental shelf in the Russian Arctic outside 200 Mile based on 1%
sediment thickness criterion. Arctic Technology Conference, Houston.
Gramberg, I.S., Demenitskaya, R.M., Sekretov, S.B., 1990. System of rift
basins in the Laptev Sea shelf: a missing link in the Gakkel—Moma rift
belt. Dokl. Akad. Nauk SSSR 311 (3), 689–694.
Gusev, E.A., Zajonchek, A.V., Mennis, M.V., Rekant, P.V., Rudoi, A.S., Rybakov, K.S., Chernykh, A.A., 2002. Gakkel Ridge extension in the Laptev
Sea, in: Geological and Geophysical Features of the Lithosphere of the
Arctic Region [in Russian]. VNIIOkeangeologia, St. Petersburg, Issue 4,
pp. 40–54.
Jakobsson, M., Mayer, L.A., Coakley, B., Mayer, L., Coakley, B., Dowdeswell, J.A., Forbes, S., Fridman, B., Hodnesdal, H., Noormets, R.,
Pedersen, R., Rebesco, M., Schenke, H.W., Zarayskaya, Yu., Accettella, D., Armstrong, A., Anderson, R.M., Bienhoff, P., Camerlenghi, A.,
Church, I., Edwards, M., Gardner, J.V., Hall, J.K., Hell, B., Hestvik, O.,
Kristoffersen, Y., Marcussen, Ch., Rezwan, M., Mosher, D., Nghiem, S.V.,
Pedrosa, M.T., Travaglini, P.G., Weatherall, P., 2012. The International
Bathymetric Chart of the Arctic Ocean (IBCAO). Version 3.0. Geophys.
Res. Lett. 39, L12609.
Jokat, W., Micksch, U., 2004. Sedimentary structure of the Nansen and
Amundsen basins. Geophys. Res. Lett. 31, L07602.
Karasik, A.M., 1968. Magnetic anomalies of the Gakkel Ridge and origin of
the Eurasian subbasin of the Arctic Ocean, in: Geophysical Exploration
Methods in the Arctic [in Russian]. NIIGA, Leningrad, Issue 5, pp. 8–19.
Karasik, A.M., Savostin, L.A., Zonenshain, L.P., 1983. Parameters of plate
motion in the Eurasian Basin of the Arctic Ocean. Dokl. Akad. Nauk
SSSR 273 (5), 1191–1196.
Kiselev, Yu.G., 1986. Deep Structure of the Arctic Basin [in Russian]. Nedra,
Moscow.
McNeil, D.H., Dud-Rodkin, A., Dixon, J., Dietrich, J.R., White, J.M.,
Miller, K.G., Issler, D.R., 2001. Sequence stratigraphy, biotic change,
87
Sr/86Sr record, paleoclimatic history, and sedimentation rate change
across a regional late Cenozoic unconformity in Arctic Canada. Can. J.
Earth Sci. 38, 309–331, doi: 10.1139/cjes-38-2-309.
Michael, P.J., Langmuir, C.H., Dick, H.J.B., Snow, J.E., Goldstein, S.L.,
Graham, D.W., Lehnert, K., Kurras, G., Jokat, W., Muhe, R., Edmonds, H.N., 2003. Magmatic and amagmatic seafloor generation at the
ultraslow-spreading Gakkel ridge, Arctic Ocean. Nature 423, 956–961,
doi: 10.1038/nature01704.
Naryshkin, G.D., 1987. Central Ridge in Eurasian Basin of the Arctic Ocean
[in Russian]. Nauka, Moscow.
Rekant, P.V., Petrov, O.V., Kashubin, S.N., Rybalka, A.V., Vinokurov, I.Yu.,
Gusev, E.A., 2015. History of formation of the sedimentary cover of Arctic
basin. Multychannel seismic approach. Regional’naya Geologiya i Metallogeniya, No. 65, 11–27.
Sekretov, S.B., 2002. Structure and tectonic evolution of the Southern Eurasia
Basin, Arctic Ocean. Tectonophysics 351, 193–243.
Svindland, K.T., Vorren, T.O., 2002. Late Cenozoic sedimentary environments
in the Amundsen Basin, Arctic Ocean. Marine Geol. 186, 541–555.
Sweeney, J.F., Weber, J.R., Blasco, S.M., 1982. Continental ridges in the
Artic ocean: LOREX constraints. Tectonophysics 89, 217–238.
Vogt, P.R., Taylor, P.T., Kovacs, L.C., Johnson, G.L., 1979. Detailed
aeromagnetic investigations of the Arctic Basin. J. Geophys. Res. 84,
1071–1089.
Weigelt, E., Jokat, W., Franke, D., 2014. Seismostratigraphy of the Siberian
Sector of the Arctic Ocean and adjacent Laptev Sea Shelf. J. Geophys.
Res. B119, 5275–5289, doi: 10.1002/2013JB010727.
Editorial responsibility: V.A. Kontorovich