RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES5002, doi:10.2205/2005ES000190, 2005

Tectonic Models for the Terrain Formation

2005ES000190-fig09
Figure 9
[69]  The results of the terrain analysis of the southeast Sakhalin and the data available for the West Sakhalin, Moneron, and Kem terrains [Golozubov, 2004; Governmental Geological Map, 2001; Malinovskii et al., 2002; Piskunov and Khvedchuk, 1976; Richter, 1986; Zyabrev, 1992], and for the correlative tectonic units of Hokkaido [Isozaki, 1996; Kiminami et al., 1992; Kiyokawa, 1992; Niida and Kito, 1986, to name but a few], suggest that the accretion-type structural features of the Hokkaido-Sakhalin fold system had formed, at least, from the Aptian to the Eocene (Figure 9).

[70]  Before describing the tectonic evolution of the region, I will first discuss the models of the South Sakhalin terrain formation and the basic processes and mechanisms of the growth of the Cretaceous-Early Paleogene East Asian margin. I believe it more expedient to begin my review with the Susunai Terrain which occupies the internal position in the assemblage of the South Sakhalin accretion-type structural features and restricts, together with the Kamuikotan Terrain, the propagation of the Cretaceous-Paleogene accretion-type rock complexes from the west.

2005ES000190-fig10
Figure 10
A model for the formation of the Susunai terrain.
The models describing the origin of the early metamorphic structure and the formation of early (pre-Late Cretaceous) metamorphic rock complexes were offered by Japanese geologists for the Kamuikotan Terrain [Sakakibara and Ota, 1994]. Like in the Susunai Terrain, in the Kamuikotan Terrain the protoliths of the amphibolite were the pre-Late Jurassic ophiolites of the Sorachi Terrain [Dobretsov et al., 1994; Komatsu et al., 1992], which are believed to have been formed in the environment of the large intraoceanic Early Mesozoic Mikabu-Sanbosan-Sorachi Plateau (which is here referred to as the Sorachi Plateau) [Kimura et al., 1994; Maruyama, 1997]. The datings of the amphibolites from South and Central Sakhalin and Hokkaido fit in the time interval of 206-145 Ma [Dobretsov et al., 1994; Egorov, 1969; Governmental Geological Map..., 2001; Khanchuk et al., 1988; Komatsu et al., 1992]. These data suggest that the metamorphic rocks of the epidote-amphibolite facies had accumulated over the larger time interval of the Triassic and Jurassic during the growth of the Sorachi oceanic plateau and the tectonic layering of its basement under the conditions of high-pressure (Figure 10a). The amphibolites experienced Early Cretaceons (135-120 Ma) lawsonite-glaucophane metamorphism wich resulted in the formation of the metamorphic rocks of metasomatic origin, widely varying from blueschists to eclogite like metasomatic rocks. As follows from the isotopic, geochemical, and petrologic studies of the rocks, the metaophiolites had been glaucophanized under the condition of high-pressure dynamic metamorphism at the depths of 25-30 km during the rapid subduction of the oceanic plate (apparently, the Izanagi Plate) with the tectonic layering and underplating of the subducted fragments of the Sorachi Plateau (Figure 10b).

[71]  Both in the Susunai and Kamuikotan terrains, the metaophiolites and Early Cretaceous high-pressure rocks were included into the Late Cretaceous metamorphic rocks and serpentinite melange as allochthonous slabs. However, they occur as large slabs in the southern segment of the Kamuikotan terrain, and merely as small tectonic slabs, subordinate to the serpentinite melange and Late Cretaceous metamorphic rocks, in the northern segment of this and also in the Susunai terrain. This suggests that the emplacements of the pre-late Cretaceous metamorphic rocks into the later accretion-subduction structural features was accompanied by their breaking into individual slabs and by their spreading in the northern direction under the conditions of left-lateral oblique subduction or transform fault movements along the continental margin.

[72]  The Kamuikotan Terrain is known for its abundant Albian-Early Cenomanian metamorphic rocks (110-95 Ma). The predominant rock is apoterrigenous shale, whereas the green and blue shales, quartzite, and metaophiolite composing a smaller number of the tectonic slabs are included into the black shale matrix [Ishizuka et al., 1983; Komatsu et al., 1992; Ota et al., 1993]. The regular patterns of this kind are usually interpreted as the involvement of the large volumes of turbidites filling the trench and composing the basal parts of the accretionary prisms. The latter include the tectonically layered fragments of the subducted oceanic plate and of the oceanic crust sediments and had experienced progressive high-pressure metamorphism beginning from the depths of 10-15 km (Figure 10c). Similar rocks seem to have been developed in the Susunai Terrain, as evidenced by singular datings of 90 Ma and 92 Ma [Egorov, 1969] obtained for amphibole-mica schists, yet, without associating them with any particular structural features. The latter circumstance does not allow one to identify them as an independent rock complex and to use them in geodynamic analysis.

[73]  It can, thus, be concluded that at the end of the Early to the beginning of the Late Cretaceous the oblique and still rapid subduction of the Izanagi Plate was accompanied by the subduction and simultaneous spreading of the fragments of the oceanic plateau along the convergence contact. Because of their sizes and lower density, compared to that of the oceanic lithosphere, the previously subducted plateau blocks might be able to block the further subduction in the southern segment of the subduction zone. In addition, Ohta [1996] suggested that the floating up of these blocks might have caused the formation of a mantle wedge and the rising of the old accretion-type structural features of the continental margin (Figure 10c). These processes might have caused the protrusion of the serpentinite melange and metamorphic ophiolites into the accretionary prism and into the basal rocks of the sedimentary rock cover, controlled by the left-lateral displacements in the rear of the accretion prism.

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Figure 11
[74]  The accretion prism grew in size, both laterally, because of the accumulation of olistostrome rock sequences and the stripping of the hemipelagic sediments from the subduction plate, and vertically, because of the subduction of the accretionary prism, the reworking of the growing volume of the sediments by the basal stripping, the formation of scaly duplexes, and the underplating of the oceanic basement slabs (Figure 11a). Below the depth level of 7-10 km the rocks experienced metamorphic transformations, and the structural pattern of the tectonically layered accretion rock complex acquired the features of a zone of dynamic metamorphic zone. This model was aprobated using the old accretion rock complexes of Japan, Alaska, and Sakhalin [Kimura et al., 1992a, 1992b].

[75]  The mechanisms discussed above are typical of the West-Susunai Subterrain, which is interpreted as the deep levels of the Late Cretaceous (85-65 Ma) zone of left-lateral subduction, which developed synchronously with the formation of the West Sakhalin turbidite basin (Figure 11b). The structural pattern of the West Susunai subterrain was shaped as a result of the long-lasting subduction of the Meso-Pacific oceanic rock complexes and of the Middle Cretaceous accretion prism in the northwestern direction. The subducted portions of the accretionary prism experienced dynamic metamorphism of the glaucophane-green schist facies. Its metaophiolites (amphibolite and serpentinite) experienced high-pressure diaphthoresis. The position of the metaophiolites (amphibolite and serpentinite) along the western flank of the subterrain suggests their involvement into the subduction structure during the early phases of its evolution and their subsequent spreading under the conditions of the left lateral subduction. The evidence of the latter is provided by the numerous small serpentinite slabs recorded between the outcrops of the Sokol and Komissarov protrusion zones (Figure 6).

[76]  At the Cretaceous-Paleogene boundary the structural features of the Late Cretaceous subduction zone were deformed to the echelon-like system of flexure-type folds with the initial exhumation and the subsequent retrograde metamorphism of the high-pressure rock complexes. These movements were accompanied by the inversion of the eastern segment of the West Sakhalin turbidite basin and by the poor prehnite-pumpelliyte facies metamorphism (K-Ar age of 59.7-61.9 Ma) of its lower parts (Figure 11c). At the western flank of the inversion zone the Campanian-Maestrichtian turbidites were cut by a rhyolite dike belt with the K-Ar age of 68 pm 2 Ma [Governmental Geological Map, 2001] of subduction-collision origin (Figures 3 and 9). In the limbs of the flexure-like folds, the high-pressure schists of the West-Susunai Subterrain had been thrust over the poorly metamorphic rocks of the West Sakhalin Terrain. The latter were eroded in the antiform fold hinges, yet, were not eroded in the synforms, being overlain by the Lower Paleocene conglomerates containing West Sakhalin aleuropelite pebbles (Figures 6 and 7).

[77]  More eastward, the poorly metamorphozed rocks of the upper structural levels of the Cretaceous subduction zone, classified as those of the East Susunai Subterrain, experienced a swell-like curvature and were collected to NE-trending slabs and folded in the NW vergence with steeply dipping hinges (Komissarov Block and Sima package of slabs). The orientation of the compression structural features and the left-lateral en-echelon type of the flexure-like folds suggest that the rocks were deformed in the tension field of the left-lateral strike-slip fault, the eastern flank of which was the Merei suture. The western flank of the Early Paleogene deformation seems to have inherited the left-lateral strike-slip fault zones along which the metaophiolites and serpentinite melanges were protruded at the boundary between the Early and Late Cretaceous (Figure 10c).

[78]  As follows from the structural analysis and isotope dating of the schists (64.5-59.2 million years), the imbricate-overthrust structure of the northern segment of the East Susunai Subterrain was formed during the middle Paleocene, synchronously with the deformation of the Cretaceous subduction zone (Figure 11c). It is interpreted as the north-trending zone of the Paleocene-Early Eocene subduction of the epi-oceanic marginal sea, the mid-Cretaceous accretion prism, and the distal parts of the turbidite basin, and is believed to have been associated with a change in the direction of the paleo-oceanic plate movement from the northwestern (314o) to the NNW one (358-338o). The structural features of the Cretaceous subduction zone and of the metamorphism, involved into the zone of the Late Paleocene-Early Eocene subduction, were tectonically layered by imbricate overthrusts and terrigenous melanges of southern vergence and superposed with the poorly metamorphic Mesozoic rocks of the East-Susunai Subterrain (Zhukovka, Sima, and Bakhura slab packages).

[79]  To sum up, the northern part of the Susunai Terrain is distinguished by the superposition of the Late Paleocene-Early Eocene sublatitudinal subduction zone over the Cretaceous submeridional, intricately deformed zone of high-pressure dynamic metamorphism and corresponds to the end-to-end junction of the structural features of the Cretaceous and Early Paleogene subduction zones.

[80]  The late metamorphic structure of the Susunai Terrain was formed during the Middle Eocene under the conditions of the single-trend compression from the northwest and reflects the mature exhumation stage of the Susunai metamorphic rocks.

2005ES000190-fig12
Figure 12
A Model for the Origin of the Aniva Composite Terrain.
The Aniva composite terrain originated as the structural unit of the Hokkaido-Sakhalin Fold System in the Middle Eocene. The structural features and the great diversity of the tectono-stratigraphic units composing its Tonin-Aniva and Ozerskii terrains suggest their separate formation up to the middle of the Paleogene. The models of the formation of these terrains are presented as paleotectonic profiles in Figure 12.

[81]  The Aptian-Cenomanian stage of the Tonin-Aniva Terrain formation agrees with the model of the Middle Cretaceous evolution of the Susunai Terrain (Figure 10c). The accretion structure of this terrain was formed in the course of the left-lateral subduction of some large intraoceanic volcanic rises, accreted to the East-Asia margin during the second half of the Early Cretaceous (Figure 12a).

[82]  The rocks of the Aptian-Cenomanian accretion complex (Utesna rock sequence) accumulated during the rapid rising of the continental margin, which was accompanied by the breakdown of the continental slope, avalanche-like sedimentation, and the formation of thick olistostrome and turbidite sequences. The olistostromes were saturated mainly with the clastics of the accreted volcanic plateau and with the products of the synchronous alkali-basaltic volcanism, whereas the turbidite rock sequences with their subarkose clastic material accumulated at the expense of the erosion of the continental land. The fact that the olistostromes contain syngenetic quartz feldspar and high-quartz sandstones, on the one hand, and the Late Permian limestones of rift origin, on the other, suggests that the Utesna rocks had accumulated in the vicinity of the old accretion-type continental margin including continental terrains (Hida, South Kitakami, and others), and the pre-Cretaceous accretion prism terrains with the fragments of Permian intraoceanic plateaus. For instance, the fragments of the Maizuru Plateau are included into the Jurassic accretion-type Honshu and SW Hokkaido terrains, such as, Mino-Tamba, North Kitakami, and Oshima [Isozaki, 1996; Kiminami et al., 1992; Kimura et al., 1994; Maruyama, 1997; Maruyama et al., 1997]. The potential sources of the Permian continental and exotic clastic material are located in the modern structure of the continental margin at least 600-800 km south of the Tonin-Aniva Terrain position. This suggests that this terrain began to form in lower latitudes.

[83]  The subsequent evolution of the accretion prism in the late Cretaceous was synchronous with the accumulation of the Late Cretaceous rocks of the Evstafiev Formation, which covered the Middle Cretaceous accretion wedge and the sediments of the oceanic plate by distal-facies turbidites. The evolution of the Tonin-Aniva Terrain in the conditions of the eastward progradation of the forearc trough of the East Sikhote Alin volcanic belt was accompanied by the displacement of the Middle Cretaceous accretion rock complex to the north along the continental margin, and by its simultaneous crowding and thrusting over the Late Cretaceous turbidite. The movements of this terrain seem to have been controlled by the left-lateral shear zones which inherited the old convergent boundaries and later bounded the Idonnappu and Merei suture-type structural features.

[84]  The specific structure of the Ozerskii Terrain explains the accumulation of its rock complexes in the environment of the ensimatic island arc (the Chaika rock sequence and the Okhotsk rock complex) and in that of epicontinental marginal sea (Upper Cretaceous-Lower Paleogene silty pelite). The Gorbusha turbidites seems to have accumulated in the same environment as the Utesna turbidites, yet, in more close association with the continental terrains which supplied quartz-feldspar and granite clastic material (Figure 12a). The presence of the Gorbusha subarkose turbidites in the para-autochthon of the oceanic rock complex can be explained by some specific mechanisms of the tectonic combination of the Ozerskii and Tonin-Aniva terrains.

[85]  The Ozerskii Terrain is composed mostly of the Paleo- and Meso-Pacific oceanic rocks which had been emplaced prior to the Campanian in the low-latitude areas, as proved by the finds of Jurassic-Early Cretaceous heat-loving radiolaria, typical of the Tethyan Provinces of the Pacific and of the Alpine Mediterranean belt, by the finds of the Cretaceous Tethyan rudists in the Kedrov rock sequence, and confirmed by paleomagnetic data [Bazhenov et al., 2001, 2002].

[86]  The Upper Permian-Middle Triassic metabasalts (Velikan sequence) correspond to the upper part of the second layer of the oceanic crust which had been formed in the environment of a mid-oceanic ridge. The Middle Triassic-Jurassic condensed jaspers of the Yunona rock sequence, overlying the basalts, suggest the environment of a deep-sea abyssal plain. The overlying Upper Tithonian-Lower Cretaceous Kedrov rocks sequence is saturated with pyroclastic material and encloses subalkaline basalt lavas. This suggests the replacement of the deep-sea siliceous sedimentation by the environment of oceanic intraplate volcanism.

[87]  The accretion rocks of the Chaika Subterrain accumulated under the conditions of deficient sediments in the forearc basin and in the trench (not more than 1 km thick). This facilitated the deep propagation of the basal breaks into the subducted oceanic crust and the substantial vertical accretion with the underplating of large oceanic crust slabs. The upper structural levels of the accretion complex of the Chaika Subterrain are composed of Campanian-Paleocene tuffaceous turbidite of the Chaika rock sequence and are intruded by Paleocene-Early Eocene diorite-granodiorite bodies of the Okhotsk Complex. The Campanian-Maestrichtian tuffaceous turbidites overlie the Santonian-Early Campanian hemipelagic sediments in the upper part of the oceanic crust, as has been found in the Chaika slab. The specific features of the lithology and structure of these rock complexes suggest that island-arc volcanic activity developed in the Campanian-Maestrichtian time, and diorite-granodiorite intrusions of type I were emplaced in the Paleocene-Early Eocene time (Figure 12c).

[88]  As follows from the paleomagnetic data available, the Campanian-Maestrichtian tuffaceous turbidites of the Chaika rock sequence had accumulated at the paleolatitude of 26.6 pm 5.2 N, or in the area about 3000 km south of their modern position [Bazhenov et al., 2001, 2002]. Similar results were obtained for the Tokoro tuffaceous turbidite [Kanamatsu et al., 1992]. This allowed us to classify these rock complexes as the constituents of the same ensimatic arc, referred to as the Tokoro arc [Bazhenov et al., 2001]. As follows from our kinematic analysis, this island arc developed at the leading edge of the Pacific plate and, consequently, the subduction was directed to the ocean. The Tokoro island arc was active up to the Middle Eocene, which is proved by the presence of Early Eocene turbidites in the accretionary rock complex of the Tokoro terrain [Kiminami et al., 1992].

[89]  Earlier, Bazhenov et al. [2001] reconstructed the system of the Late Cretaceous ensimatic arcs, which separated, during the Campanian, the segment of the Pacific Plate, which later became an epioceanic marginal sea and has been classified as the Velikan Plate in this study (see Figure 12b). The fragments of its oceanic crust and of the overlying Lower Paleogene sedimentary cover are combined tectonically in the Tunaicha Subterrain.

[90]  To sum up, the Ozerskii Subterrain was produced by the accretion of the rocks of the oceanic plate which was transformed at the end of the Cretaceous to an epioceanic marginal sea basin, yet, following different mechanisms of its formation in the Chaika and Tunaicha subterrains. The Chaika Subterrain developed as a Campanian-Early Eocene accretion prism of the ensimatic island arc with the subduction of the oceanic plate in the ESE direction, and the Tunaicha Subterrain developed as a fragment of the epioceanic marginal sea crust, accreted to the continental margin in the Paleogene.

[91]  The final stage of the formation of the Tonin-Aniva and Ozerskii terrains was associated with their combination (amalgamation) as a result of the collision of the Tokoro Arc with the continental margin and of the complete absorption of the marginal sea plate. The convergence of the terrains was accompanied by the formation of the Vavai melange zone, which happened to include the slabs of the near-continent accretion prism, oceanic crust, and island-arcs (Figure 12d). The interaction of the terrains followed the mechanism described in the model of arc-continent collision [Konstantinovskaya, 1999, 2003]. The structural features of the Tonin-Aniva Terrain were overthrust in the western direction. The eastern flank of the terrain experienced crowding and was transformed to the East Aniva slab-type overthrust zone.

[92]  During the early collision stage the accretion rock complex of the Chaika Subterrain experienced compression in the SE-NW direction and crowding along the NW-trending overthrusts. The forearc basin of the island arc was basically demolished, being preserved only as allochthonous slabs in the boundary-type Vavai melange or as the fragments bordering the igneous rock arc. That period of time seems to have been marked by the emplacement of the dikes of the second phase of the Sea of Okhotsk Complex. The late collision stage was marked by sublatitudinal compression, obviously associated with the beginning of the Pacific motion in the WNW direction 43 million years ago [Engebretson et al., 1985]. The structural features of the Chaika Subterrain and Vavai melange acquired the western vergence, and the intrusion of the collision granites of the Aniva Complex terminated the process of the terrain assemblage.

[93]  The Aniva composite terrain, which was formed after the terrain amalgamation, moved to the north along the Merei shear zone up to its final accretion to the continental margin at the end of the Eocene. The northern part of this composite terrain was included into the Paleogene subduction zone with the tectonic layering and subduction of the crust of the epioceanic marginal sea (Tunaicha Subterrain) and of the Tonin-Aniva terrain structural features (Figure 5, Profile II-II), as well as with the transverse wedge-shaped curving of the Chaika Subterrain structural features (Figure 4).

[94]  The syncontinental structural features of the Hokkaido-Sakhalin fold system form the Moneron and West Sakhalin terrains, the formation models of which are still a matter of discussion.

[95]  As follows from the modern views [Malinovskii et al., 2002; Rozhdestvenskii, 1993; Simanenko, 1986], the volcanic rocks of the Moneron and Rebun-Kobato terrains are interpreted as the rock complexes of the outer ocean-bordering part of the Early Cretaceous Moneron-Samarga island arc. The volcanogenic sediments of the East Sikhote Alin, interpreted as the Kem Terrain [Golozubov, 2004; Khanchuk, 1993; Malinovskii et al., 2002], were ranked as the rear part of the arc and as the back-arc basin. It is believed that after the accretion of the arc and the closure of the back-up basin at the boundary between the Early and Late Cretaceous, their rock complexes were covered by the rocks of the East Sikhote Alin volcanic belt. The terrigenous rocks of the Iezo and West Sakhalin terrains are treated, in terms of this view, as the rocks of the forearc trough, which had accumulated during the Early Cretaceous in front of the island-arc, and as the rocks that had accumulated during the Late Cretaceous-Paleocene, which grade eastward to the Cretaceous-Paleogene accretion-type rocks of Central Hokkaido and East Sakhalin [Melankholina, 1988; Rozhdestvenskii, 1993; Zyabrev, 1992]. The modern positions of the outer and inner parts of the Moneron-Samarga Arc are explained by the shear and pull-apart tectonic movements associated with the opening of spreading basins in the Sea of Japan and in the southern segments of the Tatar Strait.

[96]  As follows from the data published in the literature [Piskunov and Khvedchuk, 1976], the volcanic rocks of the Moneron Terrain could be layered tectonically into at least four rock sequences ranging from 250-400 m to 1500-1800 m in thickness and from Cretaceous to Paleocene in age, being irregularly distributed over the rock sequence, yet, grouping into four age intervals: 141, 118, 103-86, and 77-59 Ma. The structural and lithologic transformations of the basalts grow more intensive progressively toward the tectonic contacts of the blocks and generally down the rock sequence. This explains the significant scatter of the ages by their rejuvenation as a result of the post magmatic thermal events which seem to have been associated with the tectonic movements of the island-arc terrain. In this case, proceeding from the Upper Cretaceous age of the overlying deposits, it can be assumed that the oldest basalts (141-118 Ma) date the initial age of the rock complex which correlates well with the Berriasian-Barremian age of the volcanic rocks composing the Rebun-Kobato Terrain.

[97]  The correlation of the Moneron and Kem terrains is not that easy in connection with the recently published new data [Malinovskii et al., 2002]. The volcanic rocks of these terrains vary in age (Berriasian-Barremian and Late Aptian to Early Albian), whereas the sedimentation model and the arcose composition of the turbidites, underlying the Kem volcanics, contradict the view that an active island arc had existed at that time east of the Kem Terrain.

[98]  The model of the formation of the West Sakhalin Terrain was discussed by S. V. Zyabrev. He proved that its Cretaceous rock sequence is composed of classic turbidites which had accumulated in the transit and discharge area of the fan-valley systems of the continental slope, oriented from the west to the east and southeast.

[99]  The turbidites had accumulated in a cyclic manner, which is recorded in the vertical sequence of the distal and proximal facies. In the southern part of the West-Sakhalin Trough, the most significant change of the distal sedimentation environment to the proximal one is recorded at the end of the Albian to the beginning of the Cenomanian and was associated with the rapid protrusion of the fan-valley systems to the east. In the Early Turonian they retreated, and merely distal sedimentation environment existed up to the Campanian, which later was substituted again by the proximal one [Zyabrev, 1984]. The Late Senonian progradation of the basin correlates well with the development of the East Sikhote Alin volcanic belt and with the displacement of the tectonic and igneous activity toward the ocean, the development of the proximal facies at the boundary between the Early and Late Cretaceous can be explained by the structural rearrangement of the transition zone.

[100]  The Aptian-Albian turbidites of the Iezo Terrain and of the southern part of the West Sakhalin Terrain, compared to its northern part, are notably poor in the synchronous pyroclastics, include single thin acid-intermediate tuff layers, yet are enriched in quartz-feldspar grains up to the formation of oligomictic quartz-feldspar sandstone beds. This suggests that during the later half of the Early Cretaceous the southern segment of the Iezo-West Sakhalin basin developed at a significant distance from the region of island-arc volcanic activity, residing, on the contrary, in the region of continental margin erosion. Only the end of the Albian was marked by the significant effects of the rises composed of volcanic rocks (Moneron and other rises), which controlled the development of proximal turbidite facies. However, they supplied basaltic andesite epiclastic material, which proves them to be structural rather than volcanic rises. This agreed with the timing of the tectonic movements of the Rebun-Kobato and Moneron terrains.

[101]  As follows from the biogeographic, geochronological, and structural data, the Aptian-Albian period was the time of the large left-lateral movements (up to 1500-2000 km) of the Central Japan ocean-bordering terrains along the Tanakura, Kurosegawa, Ivaizumi, and other transregional shear zones [Golozubov, 2004; Isozaki, 1996; Maruyama et al., 1997; Tazawa, 1993, to name but a few]. It appears that the formation of the Kem Terrain and of the Aptian-Early Cenomanian part of the West Sakhalin Terrain might have been associated with these tectonic movements. One of the potential versions of the formation of the Aptian-Albian alkaline volcanics of the Kem Terrain is their development in the environment of the left-lateral movements of the internal areas of the transition zone, which were lower than those in the perioceanic region. Following this view, the Iezo and West Sakhalin terrains were formed in the Early Cretaceous as a turbidite trough in the Asian margin, similar to the troughs of the Sikhote Alin fold zone, e.g., the Zhuravlev Terrain [Golozubov and Khanchuk, 1995]. During the Late Cretaceous, after the accretion of the oceanic (Sorachi) and island-arc (Moneron and Rebun-Kobato) terrains or after their movements along the margin of the large oceanic ridge and after the rearrangement of the transition zone, these terrains began to develop synchronously with the evolution of the East Sikhote Alin volcanic belt as a fore-arc continental margin trough.

[102]  Using the models proposed in this study for the formation of the South Sakhalin terrains, we carried out the tectonic reconstruction of the region. Discussed below are the main periods of its geodynamic evolution.


RJES

Citation: Zharov, A. E. (2005), South Sakhalin tectonics and geodynamics: A model for the Cretaceous-Paleogene accretion of the East Asian continental margin, Russ. J. Earth Sci., 7, ES5002, doi:10.2205/2005ES000190.

Copyright 2005 by the Russian Journal of Earth Sciences

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