Jurassic Dextral and Cretaceous Sinistral Movements Along the Hida Marginal Belt

Gondwana Research, V 6, No. 4, pp. 687-698. 0 2003 International Association for Gondwuna Research, Japan ISSN: 1342-937X

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Gondwana , Research

Jurassic Dextral and Cretaceous Sinistral Movements Along the Hida Marginal Belt Kazuhiro Tsukada The Nagoya University M U S ~ Z LNagoya W I , 464-8601, Japan (Manuscript received June 28, 2002; accepted March 25, 2003)

Abstract Thc Hida marginal bclt (HMB), which consists of various kinds of fault-bound blocks, is located bctwccn the continental inassif of the Hida bclt and the Mesozoic accrctionary cornplcx of the Mino belt in Ccntral Japan. Detailcd field investigation reveals that thc HMB had grown through the two diffcrcnt movements, i.c.,Jurassic dextral and Crctaceous sinistral movcmcnts. The Jurassic dextral ductile shcar zones run in the southcrn marginal part of thc Hida bclt and the northern part of thc HMB, whereas the Cretaceous sinistral cataclastic shear zones occur in the southcrn part of the HMB and the northern marginal part of the Mino belt. Geologic map and field cvidcncc sccin to suggest that the Jurassic dcxtral movcmcnt form thc fault-bound blocks of the HMB to form the basic structure of the Hida marginal bclt, i.c., formation of thc ‘proto-HMB.’Following thc dextral movcment, thc sinistral onc rcstructurcd the ‘proto-HMB’ to complctc thc prcscnt feature of thc Hida marginal belt. The Cretaceous sinistral movcment might result in the sinistral collision betwccn thc proto-HMB and the Mino belt. Key words: Hida marginal belt, shcar zoncs, Jurassic and Cretaceous movements, southwest Japan.

Introduction The geology of the East Asian contincntal margin developed through various processes such as accretion, collision and strilte-slip tectonic movement. Accretion of trench-fill sediments and oceanic plate cover, as well as collision of terraiies with strike-slip tectonic movement created the basic geotectonic framework of SW Japan. Features of the accretionary complexes of SW Japan have been studied and various tectonic models for their formation have been presented (e.g., Wakita, 2000). However, the process of the collision and the role of the strike-slip tectonic movement in the evolution of SW Japan have not been precisely explained. In SW Japan, the Hida, Sangun, Akiyoshi, Maizuru, Ultra-Tamba and Mino bclts are distributed from north to south in the Inner Zone of SW Japan, i.e., on the north of MTL (Fig. 1).The Sangun, Akiyoshi, Maizuru, and UltraTamba belts are widely exposed in the western part of SW Japan, but are absent in the eastern part of SW Japan. The Hida marginal belt, which includes fault-bound blocks derived from the Sangun, Akiyoshi and Maizuru belts and Paleozoic shelf facies rocks (e.g., Chihara et al., 1979) is distributed in a narrow zone between the Hida and Mino belts in eastern part of SW Japan (Fig. 1). The blocks derived from the Paleozoic shelf facies rocks can be divided

into the two types based on their lithostratigraphy (Waltita et al., 2001). Judging from the distribution of the belts of the Inner Zone, the Hida marginal belt may be interpreted as a tectonic zone formed by the collision of the Hida and Mino belts. In order to examine this hypothesis, analysis of rock distribution and fabrics of shear zones in and around the Hida marginal belt is necessary. In this paper, the stratigraphy, the rock distribution and the fabrics in the shear zones in the Fukuji-Takayama area, including the Hida belt, the Hida marginal belt and the Mino belt central Japan, are discussed in order to consider the evolution of thc Hida marginal belt.

Geological Setting of Southwest Japan The Japanese Islands are geographically divided into SW Japan and NE Japan by Itoigawa-Shizuoka Tectonic Line, and SW Japan is subdivided into the Inner Zone and the Outer Zone by the Median Tectonic Line (Fig. 1). The Inner Zone of SW Japan is composed of the following belts, Hida belt, Hida marginal belt, Mino belt, Ryoke belt, Altiyoshi belt, Sangun belt, Maizuru belt, Ultra-Tamba belt and Nagato tectonic belt (Wakita, 1989; Wakita et al., 1992, Fig. 1).The Hida and Sangun belts consist mainly of Paleozoic and Mesozoic metamorphic rocks, and the Ryolte belt is of the metamorphosed accretionary complex

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of the Mino belt (e.g., Geological Survey of Japan, 1992). The Akiyoshi and Ultra-Tamba belts are characterized by Permian accretionary complexes, whereas the Mino belt is Jurassic (e.g., Geological Survey of Japan, 1992). The Maizuru belt is an upper Paleozoic island arc system covered by Upper Paleozoic to Lower Mesozoic strata (e.g., Geological Survey of Japan, 1992). The Nagato tectonic belt is considered to be the western extension of the Hida marginal belt. Most of these belts occur as subhorizontal or gently-northward-dipping thin tectonic units and form a huge pile of nappes in the western part of the Inner Zone of SW Japan (e.g., Isozaki et al., 1990). The Sangun, Akiyoshi, Maizuru, and Ultra-Tamba belts are widely exposed in the western part of SW Japan, whereas these belts are absent and the Hida marginal belt is relatively narrowly distributed between the Hida and Mino belts in the eastern part of SW Japan (Fig. 1). It is generally considered that the Jurassic accretion of the Mino belt formed the nappe system in the western part of the Inner Zone of SW Japan, and stacking of nappes of the Sangun, Akiyoshi, Maizuru and Ultra-Tamba belts was enhanced during Jurassic time (e.g., Hayasaka, 1990; Ichikawa, 1990). This means that the Sangun, Akiyoshi, Maizuru, Ultra-Tamba and Mino belts must have been

amalgamated by the Jurassic. In this paper, the term ‘Outer belt’ will be used for the amalgamated Sangun-AkiyoshiMaizuru-Ultra-Tamba-Mino belt for convenience. Paleomagnetic reconstruction indicates that the Japanese Islands were arranged in a northeast direction before the opening of the Sea of Japan in the Middle Miocene (Otofuji et al., 1985, Fig. 1).Most of the belts in Japan did not extend to Korea, but run on the east of the Korean Peninsula trending north to northeast, although part of the Hida belt may have extended to the Gyeonggi or Yeongnam Massif of Korea (Otoh et al., 1999). This means that the Hida belt was likely a part of the China block before the opening of Sea of Japan, but the rocks of the other belts in Japan have different origins and evolutionary histories (Otoh et al., 1999).

Geological Framework of the Hida Marginal Belt The Hida marginal belt was first defined by Kamei (1955 in Nozawa, 1978) as a complex zone dividing the continental massif of the Hida belt and the ‘Paleozoic geosynclinal facies’ rocks of the Mino belt (Fig. 2). It has been dealt with as follows: a late Paleozoic geosyncline

Legend ETI] Hidd belt @# Sdngun belt I2

Akiyo5hi belt

Maizuru belt

Ultra-Tarnba belt Mino belt (Ryoke belt included)

FTj

Hidd marginal belt and Nagato tectonic belt Rocks of the Outer Zone

Fig. 1. Tectonic map of southwest Japan before the opening of the Sea of Japan. The tectonic subdivision of Wakita et al. (2001) and Otoh et al. (1999) is followed. Present features of the Japanese Islands are shown with pale lines. MTL, ISTL, TTL, HMB and NTB show the Median tectonic line, Itoigawa-Shizuoka tectonic line, Tanakura tectonic line, Hida marginal belt and Nagato tectonic belt, respectively.

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which evolved into a narrow tectonic zone in late Jurassic time (Kamei, 1955 in Nozawa, 1978), a serpentinite mklange zone caused by the tectonics forming the ‘Hida Nappe’ (Komatsu, 1990; Chihara and Komatsu, 1982; Soma and Kunugiza, 1993) that overthrust from the Hida belt onto the ‘Outer belt,’ and a complex zone formed by several stages of movements from Permian to Jurassic times (Kimura et al., 1993). The Hida marginal belt consists of various kinds of faultbound blocks; e.g., blocks derived from the ‘Outer belt’ such as the Sangun, Altiyoshi and Maizuru belts (e.g., Chihara et al., ‘1979; Komatsu, 1990; Nishimura, 1990; Takeuchi, 1998; Kawai and Takeuchi, 2001), and blocks derived from the Paleozoic shelf-facies rocks (Fig. 3). The blocks derived from the Paleozoic shelf-facies rocks can be divided into the following two types based on their lithostratigraphy: (1)blocks composed mainly of Devonian limestone, Carboniferous limestone and Permian clastic and pyroclastic rocks (named as the Fukuji-type block), (2) blocks composed mainly of Devonian felsic tuffaceous clastic rocks, Carboniferous mafic pyroclastic rocks and Permian clastic rocks (named as the Moribu-

a

Mcsozoic to Cenomic cover rock4

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type block) (Fig. 3). In the eastern part of the Hida marginal belt, equivalents of the Sangun, Akiyoshi and Maizuru belts, which trend north to northeast and dip west, have been overthrust by the Hida belt with shear plane trending northeast and dipping west (e.g., Komatsu, 1990). In other places, the rocks of the Hida marginal belt trend east and dip subvertically. The contact between the Hida marginal belt and the Mino belt is a shear zone with foliated fault rocks. Foliation in the shear zone generally trends east and dips southward to subvertically. In this paper, the focus is on the shear zones in and around the Hida marginal belt and the blocks derived from the Paleozoic shelf-facies rocks. The geological setting of the Fukuji-Takayama area, which is the type locality of the Fukuji- and Moribu-type blocks is described.

Geological Description of the FukujiTakayama Area Structure, stratigraphy and paleobiogeography In the Fukuji-Takayama area, the Moribu-type block, the Lower Cretaceous beds of the Tetori Group (Maeda,

Sea of Japan

Funatsu Granite Rock\ of the Htda marginal belt Schist

0Gneijs /

Fault

1km Fig. 2. The distribution of the gneiss, schist, and Funatsu Granite in the Hida belt and rocks of the Hida marginal belt (modified from Nozawa, 1977 and Hiroi, 1981). ISTL-Itoigawa-Shizuoka tectonic line. See figure 1 for the locality.

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Hida marginal belt

Hida belt

Mino belt

N Tertiary

MoribuOrigindl ruck\ ot

Akiyoshi belt equivalent of the Saiigun belt

quivalent of' he Maizuru FukujiNelt type

L z l

Legend

:

1111111 Chert

; Felsic volcanic rocks and L

L

L

tuffxeous clastic rocks

,',:,'.:,..'.. .,.',.,.'...'....Post-Triassic

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Granite

$-@$ Siliceous shale ........,I

:{${$$: ........ Conglomerate

Sandstone and mudstone

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Basalt Gabbro

shallow to

........... ...... ............. non-marine sediments

....

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. . l ^ ^

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S Serpentinite rnklange Limestone Tuffaceous clastic rocks

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Fig. 3 . Stratigraphic summary of the Hida and Mino belts and the Hida marginal belt. The Mino belt is represented by the reconstructed ocean plate stratigraphy of the Funafuseyama unit (Wakita, 2000). Although radiometric ages of the Funatsu Granite show one peak at around 180 Ma, minor plutons have the radiometric ages of 200-250 Ma (Shibata and Nozawa, 1982; Ota and Itaya, 1989). G-Group, Gr-Granite, E-Early, M-Middle, L-Late, P-Paleogene, N-Neogene.

1958) and the Fukuji-typeblock are distributed in the Hida marginal belt from north to south between the Hida and Mino belts (Fig. 4). Although the pre-Cretaceous rocks in the area generally trend east to northeast and steeply dip northward or subvertically, they trend north and steeply dip westward around the Moribu (Fig. 4). The Moributype block, the Lower Cretaceous beds of the Tetori Group and the Fukuji-type block are bounded by shear zones with each other. Some shear zones can be seen in the Moribu-type block and the northern marginal part of the Mino belt (e.g., Sasaki et al., 2001; Fig. 4). The Moributype block is subdivided into several fault-bound blocks by the shear zones. A shear zone bound the Moribu-type block and the Upper Triassic Tandodani Formation around the Hongo (Tsukada et al., 1997).

The Moribu-type block in the study area is composed of the Devonian Rosse (mainly felsic tuff), Carboniferous Arakigatva (mainly mafic volcanic rocks), and Lower Permian Moribu (mainly clastic rocks) formations (e.g., Isomi and Nozawa, 1957; Igo, 1990; Tazawa et al., 2000; Wakita et al., 2001, Fig. 5). The Arakigawa Formation conformably or unconformably underlies the Moribu Formation (Horikoshi et al., 1987; Wakita et al., 2001). The Fukuji-type block is composed of the Upper Silurian (?> to Devonian Yoshiki (felsic tuffaceous clastic rocks), Devonian Fukuji (mainly limestone), Carboniferous Ichinotani (mainly limestone), Lower Permian Mizuyagadani (mainly clastic rocks), and Lower Permian Sorayama (mainly mafic volcanic rocks) formations (e.g., Igo, 1990; Tsukada and Takahashi, 2000; Wakita Gondwana Research, V 6, No. 4, 2003

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et al., 2001, Fig. 5). Although most of the formations in the Fukuji-type block are presently in fault contact with each other, they are interpreted to form a primarily conformable or unconformable succession, because the Permian formations include abundant clasts derived from the Devonian to Carboniferous formations (Igo, 1990; Tsukada and Takahashi, 2000; Wakita et al., 2001). Sandstone and mafic tuff of the Moribu-type block as well as gneiss of the Hida belt are intruded by the Funatsu Granite (Figs. 2, 3, 4). K-Ar and Rb-Sr radiometric ages of the Funatsu Granite show one peak at around 180 Ma, and minor plutons shdw radiometric ages of 200-250 Ma (Ota and Itaya, 1989; Shibata and Nozawa, 1982). The Middle Jurassic to Lower Cretaceous Tetori Group unconformably overlies the Funatsu Granite (Figs. 3, 4). The Mino belt in the area is composed largely of melange including various kinds of slabs and blocks (Wakita, 1988; Waltita, 2000) (i.e., sandstone, mudstone, felsic tuff, bedded chert, limestone, and mafic volcanic rocks) set in a muddy matrix (Fig. 2). Some slabs in the melange are enormous, and the largest one reaches 1km in width and extends as long as 5 km. Limestone blocks yield Carboniferous to Permian fusulinaceans (Isomi and Nozawa, 1957; Kojima, 1984). Permian to lower Middle Jurassic radiolarians are obtained from chert blocks

(Kojima, 1984). The muddy matrix and felsic tuff blocks yield Middle Jurassic radiolarians (Kojima, 1984). Judging from the fossil data, the age of accretion is considered to be Middle Jurassic. The all pre-Lower Cretaceous rocks of the area are unconformably covered by undeformed uppermost Cretaceous to Quaternary volcanic rocks (Fig. 3). In the eastern part of the area, the rocks of the Hida marginal belt and the Mino belt underwent contact metamorphism by the intrusion of earliest Tertiary to Quaternary granitoids (Fig. 4). The Lower Permian beds of the Moribu-type block yield brachiopods forming a mixed fauna of Boreal and Tethyan species which have close faunal affinity to those from Inner Mongolia ( e g , Tazawa, 1991, Fig. 5). The fusulinacean genus Monodiexodina, which commonly occurs on northeast China, Mongolia, and Siberia is also found from the Lower Permian beds of the Moribu-type block (e.g., Ishii et al., 1985; Tazawa et al., 1993, Fig. 5). Coeval beds of the Fukuji-typeblock, in contrast, yield a typical Tethyan fusulinacean fauna having close faunal affinity to that from the South China (Tsukada et al., 1999; Tsukada and Takahashi, 2000, Fig. 5). Lower Cretaceous beds of the Tetori Group in the area yield a ‘Tetori-type’ flora having a close affinity to that of North China and Siberia (Kimura, 1987; Maeda, 1958).

Cwer rocks

Funatsu Granite

Pukuji-type

Tcrtiary to Quarternary granites

Accretionary complex

Moribu-type

@ Rocks of the

[3 Tetori Group %%%%W

Dextral shear zones

other blocks ~~~~~

Sinistral shear zones

691

~

I

Hida marginal belt

Fault

Fig. 4. Simplified geological map of the Fukuji-Takayama area showing the distribution of shear zones. See figure 2 for the locality. HMB-Hida marginal belt.

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Moribu-type

Fukuji-type

Mixed fauna of Tethyan and Boreal * - - - - - - -

...............

I

unconformitv ? 1

unconformitv ? I

............. ........... ........... ............. ............. .rakigawa F.: ............. ............. ........... ........... ............. ........... ............. ........... ............. ........................ * * * n * * * f i * * *

* * * *

.-..- *

-7

I

*

*

A

n

n

I

Legend Mafic to intermediate pyroclastic rocks and tuffaceous clastic rocks

Conglomerate

Felsic tuff and tuffaceous clastic rocks

Limestone

Sandstone and mudstone

Description of shear zones Ductile shear zones occur in the southern margin of the Hida belt and the Moribu-type block (Fig. 4). The ductile shear zones in the Hida belt cut the Funatsu Granite to form augen gneiss (Fig. 6a). The shear zones in the Funatsu Granite are composed of mylonite, and have a northeast-trending subvertical foliation with a subhorizontal lineation. In the mylonite, fragments of quartz are strongly deformed and dynamically recrystallized.

Fig. 5. Schematic columnar sections of the Fukuii-type and Moributype blocks -in the FukujiTakayama area. F-Formation.

The foliation in the ductile shear zones is mainly defined by dimensional preferred orientation of micas. In mesoto microscopic observation, various kinds of shear sense indicators showing a dextral sense of shear, e.g., shear band (White, 1979), S-C fabric (Berthe et. al., 1979) and asymmetricpressure shadows, are observed in the mylonite. The shear zones in the Moribu-typeblock are composed mainly of schistose rocks derived from mafic tuff and clastic rocks, and have bedding-parallel foliation and Gondwana Research, V 6, No. 4, 2003

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subhorizontal to subvertical lineation. The shear zones trend east and steeply dip northward or subvertically around the Kamihirose and Hongo, whereas, they trend north and steeply dip westward around the Moribu (Fig. 4). Toward the east, around the Moribu, the schistose rocks gradually shift into the foliated cataclasite.

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In the western part of this area, the schistose rocks are dynamically recrystallized and fragments of quartz show wavy extinction (Fig. 6b). The foliation in the Moributype block is defined by concentration and dimensional preferred orientation of metamorphic minerals such as chlorite and muscovite (Fig. 6b, c). In meso- to microscopic

Fig. 6. Photographs showing the meso- and microstructure of the fault rocks of the dextral shear zones in the Fukuji-Takayama area. All photomicrographs show the sections cut perpendicularly to the foliation and subparallel to the lineation. (a) Outcrop of the mylonite developed in the Funatsu Granite. The mylonite is composed largely of porphyroclasts of K-feldspar surrounded by fine-grained quartz and plagioclase. (b-d) Photomicrographs of the sheared rocks in the Moribu-type block. (b) Schistose rock derived from sandy mudstone of the Moribu Formation. Quartz grains are dynamically recrystallized and show wavy extinction. Concentration and dimensional preferred orientation of muscovite (upper white part) define the foliation. (Crossed polars) (c) Schistose rock derived from mudstone of the Moribu Formation. Asymmetric pressure shadows on intensely elongated quartz grains (white grains) show a dextral sense of shear. Muscovite (dark part) is arranged parallel to the foliation. (Plane polarized light) (d) Schistose rock derived from mafic tuff of the Arakigawa Formation. Asymmetric structures clearly indicate a dextral sense of shear. (Plane polarized light) (e) Metamorphosed sheared rock. The rock is intruded by the Funatsu Granite, and is metamorphosed at least into the epidote-amphibolite facies. The rock is composed largely of actinolite, hornblende, epidote and plagioclase. Asymmetric tail on a grain in the middle part (black arrow) shows a dextral sense of shear (Plane polarized light).

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observation, various kinds of shear sense indicators showing a dextral or top-to-the-east sense of shear, e.g., asymmetric pressure shadows and asymmetric folds, are observed in the sheared rocks (Fig. 6c, d). The sheared rocks in the Moribu-type block are intruded by the Funatsu Granite and are metamorphosed at least into the epidote-

amphibolite facies in the eastern part of this area, around Fukuji (Fig. 6e). There is a remarkable shear zone between the Fukujitype block and the Lower Cretaceous clastic rocks of the Tetori Group (Fig. 4). The shear zone is commonly several meters wide. The rocks in the shear zone are composed

Fig. 7. Photographs showing the meso- and microstructure of the fault rocks of the sinistral shear zones in the Fukuji-Takayama area. All photographs show the sections cut perpendicularly to the foliation and subparallel to the lineation. (a-d) The sinistral shear zone along the boundary between the Sorayama Formation (Fukuji-type block of the HMB) and the Tetori Group. (a) Polished surface of cataclasite derived from mudstone of Tetori Group. Abundant elongated sandstone fragments (white arrows) are contained in a matrix of foliated mudstone. (b) Polished surface of foliated cataclasite derived from sandstone of the Tetori Group. The rock has the P-Y fabric and the o-type asymmetric in the figure) indicating a sinistral sense of shear. The P-surface has a spacing interval of several 100 pni and changes into the structure (‘0’ Y-surface at its termination. ‘Y’ and ‘P‘ in the figure show the directions of Y- and P-surfaces, respectively. (c) Photomicrograph of foliated cataclasite derived from sandstone of the Tetori Group showing the R1-type Riedel shear plane (black arrow). (d) Photomicrograph of cataclasite derived from sandstone of the Tetori Group showing drag of a broken grain (small arrow). Large arrow shows a shear plane parallel to the foliation. (Crossed polars) (e) Polished surface of foliated cataclasite derived from clast-bearing mudstone of the Mino belt including limestone clasts. Limestone clasts (white part) are intensely elongated. The R1-type Riedel shear plane (black arrows) and asymmetric folds can be seen in the rock.

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Upper Cretaceous to Quaternary

Rocks of the Hida marginal belt Rocks of the Mino Belt Shear zone Foliation Lineation

Fig. 8. Distribution of sinistral she3r zones in the northern marginal part of the Mino belt. The stereograms show the strike and dip of foliations and the trend of lineations. See figure 4 for the locality. HMB-Hida marginal belt, R-River.

mainly of fissile foliated cataclasite derived from sandstone and mudstone of the Tetori Group (Fig. 7a). Rocks in the shear zone are not recrystallized and they have a northeast-trending subvertical foliation with a subhorizontal lineation. The foliation is subparallel to the boundary between the Tetori Group and the Fukuji-type block. The cataclasite commonly contains elongated irregular- or columnar-shaped sandstone fragments in a matrix of foliated mudstone (Fig. 7a). The foliation in the muddy matrix is defined by dimensional preferred orientation of fine-grained micas and clay minerals. Foliated cataclasite derived from the sandstone of the Tetori Group is also observed in the shear zone. The foliation in the sandstone cataclasite is defined by thin layers of fine-grained micas, clay minerals and opaque minerals. Paralell foliation can be seen in the sandstone cataclasite with a spacing of several tens of microns to several millimeters (Fig. 7b). The fragments in the sandstone cataclasite which have parallel foliation are intensely elongated. In meso- to microscopic observation, Gondwnna Research, V. 6, No. 4, 2003

various kinds of shear sense indicators showing a sinistral sense of shear, e.g., Riedel shear of R1-type (Logan et al., 1979), P-Y fabric (Rutter et. al., 1986), asymmetric pressure shadows and asymmetric folds, are commonly observed in the foliated cataclasite (Fig. 7b, c, d). Some shear zones run in the northern marginal part of the Mino belt (Sasaki et al., 2001; Niwa et al., 2002, Figs. 7e, 8). Shear zones are commonly several meters to 500 m wide. They are east-trending with a vertical to south-dipping foliation and subhorizontal or south- to southwest-plunging lineations in the western part of the area (Fig. 8). The foliation in the eastern part of the area trends northeast and dips northwest, and the lineation plunges west to southwest (Fig. 8).The trends of the shear zones are parallel to the boundary between the Hida marginal belt and the Mino belt (Fig. 4). The shear zones are composed mainly of foliated cataclasite derived from melange of the Mino belt. The cataclasite commonly includes lenticular fragments of chert, sandstone, limestone and mafic volcanic rocks in foliated muddy

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matrix. The foliation in the muddy matrix is defined by thin dark layers of fine-grained micas and clay minerals. In some places, parallel foIiation can be observed in the muddy matrix with a spacing of several microns to several tens of microns (Fig. 7e). The clasts in the muddy matrix exhibiting parallel foliation are intensely elongated in general. Most of the cataclasites are not recrystallized, but rare ductile shear zones (about a few hundred microns in wide) are found at the northern edge of the Mino belt. In the ductile shear zones, fragments of quartz are strongly deformed and dynamically recrystallized. R1-type Riedel shears (Logan et al., 1979) and P-Y fabrics (Rutter et. al., 1986) clearly showing sinistral sense of shear are seen in the cataclasite (Fig. 7e). Under the microscope, various kinds of shear sense indicators showing a sinistral or top-to-the-eastsense of shear, e.g., asymmetric folds and asymmetric pressure shadows, are commonly observed in the cataclasite. Sasaki et al. (2001) mentioned that the cataclastic shear zones in the north of Hiyomo (Fig. 8) together form a sinistral strike-slip imbricate fan.

Discussion and Conclusions Timing of the shearing In the Fukuji-Takayama area, the dextral and sinistral shear zones are recognized. The dextral shear zones in the Hida belt cut the Funatsu Granite to form augen gneiss. The dextral shear zones in the Moribu-type block are intruded by the Funatsu Granite, and limit the distribution of the Upper Triassic Tandodani Formation (Fig. 4). Magnetic foliation and lineation subparallel to the foliation and lineation in the dextral shear zones in the rocks of the Hida belt and the Moribu-type block occur in the undeformed Funatsu Granite (Otoh et al., 1996). These facts suggest that the dextral shearing took place toward the Jurassic. A sinistral shear zone occurs along the boundary between the Tetori Group and the Fukuji-type block in the Fukuji-Takayama area. Maeda (1958, 1959) reported some bivalves and ‘Tetori-type’ plant fossils from the Tetori Group of the area, and correlated the fossil-bearing beds to the Lower Cretaceous beds of the Tetori Group of the type locality. The sheared rocks in the FukujiTakayama area are unconformably covered by undeformed volcanic rocks. The lower part of the volcanic rock succession yields t h e Maastrichtian palynoniorphs (Kasahara, 1979). The sheared rocks are intruded by undeformed granitoids dated around 64 Ma (Harayama, 1990). Hence, it is obvious that the sinistral shearing lasted after the early Cretaceous and had finished by the latest Cretaceous.

Development of the Hida Marginal Belt The lithostratigraphical and paleobiogeographical data strongly suggest that the Moribu-type and Fukuji-type blocks were formed in different regions at least by the Middle Permian. The Funatsu Granite intrudes into the Moribu-type block as well as the gneiss of the Hida belt (Figs. 2, 3, 4). The Middle Jurassic to Lower Cretaceous Tetori Group unconformably overlies the Funatsu Granite (Figs. 3,4). This indicates that the Moribu-type block must have been juxtaposed against the Hida belt by the Jurassic. The timing of juxtaposition of the Fukuji-type block against the Hida belt and the Moribu-type block is unknown because there is no data suggesting the Mesozoic position of the Fukuji-type block. Maeda (1961) mentioned that the Fujikuradani Formation, which might be correlated with the Ichinotani Formation of the Fukuji-type block is unconformably overlain by the Middle Jurassic beds of the Tetori Group in the western part of the Hida marginal belt. Given that this view is correct, the Fukuji-type block may have been juxtaposed against the Hida belt by the Middle Jurassic. The Jurassic dextral shear zones run in the northern part of this area, i.e., Hida belt and Moribu-type block, whereas the Cretaceous sinistral shear zones occur in the southern part of this area and bound the Tetori Group, the Fukuji-type block and the Mino belt (Fig. 4). Otoh et al. (1999) mentioned that the dextral shear zones in this area resulted from t h e northward drifting of t h e continental side. Geological map and field evidence seem to suggest that the Jurassic dextral movement caused the fragmentation of the Moribu-type block to form the basic structure of the Hida marginal belt, i.e., formation of the fault-bound blocks. Following t h e d e x t r a l movement, t h e sinistral movement took place along the eastern margin of Asia in the Cretaceous (e.g., Ozawa 1987; Tashiro, 1994; Otoh and Yanai, 1996). The sinistral shearing in this area was presumably attributed to this Cre t ace ous sinj s tral movement. It is likely t h a t t h e sinistral shearing restructured the ‘proto-Hida marginal belt’ to complete the present feature of the Hida marginal belt. The Cretaceous sinistral movement might result in the sinistral collision between the proto-Hida marginal belt and the Mino belt.

Acknowledgments I wish to thank Prof. M. Adachi, Associate Prof. M. Takeuchi, and Associate Prof. H. Yoshida of Nagoya University for helpful discussion and advice. I am indebted to Prof. S. Kojima of Gifu University, Dr. K. Wakita of Geological Survey of Japan, Associate Prof. S. Yamakita Goiidwann Research, I/: 6, No. 4, 2003

DEXTRAL AND SINISTRAL MOVEMENTS HIDA MARGINAL BELT

of Miyazalti University, Prof. Emeritus H. Igo of University of Tsultuba and participant of the field worltshop (FW-C1) of ISRGA of 2001 for valuable discussion. I would liltc to thank Mr. M. Niwa, Ms. K. Hotta and Mr. S. Tanaka of Nagoya University for valuable suggestion during the course of this work. The work was supported by Grantin-Aid of Fukada Geological Institute and Grant-in-Aid of Fundamental Scientific Research (Nos. 10003433 and 11740278) from the Ministry of Education, Science and Culture, Japan. Special thanks go to Prof. J. Aitchison of University of FIong Kong and Associate Prof. S. Otoh of Toyama University fo? critical reading- of the manuscript.

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