Tectonophysics - Elsevier Publishing Company, Amsterdam Printed in The Netherlands

LATE CENOZOIC OROGENY IN JAPAN

T. MATSUDA, K. NAKAMURAI and A. SUGIMURA2

IEarthquake Research Institute, University of Tokyo (Japan) keological Institute, University of Tokyo, Tokyo (Japan)

(Received November 7, 1966)

SUMMARY

Late Cenozoic tectonic maps are serially given to show the amount of vertical displacement since Miocene, trends of fold axes and degree of de- formation of sedimentary rocks in Japan. They illustrate some differences between the east Japan and west Japan arc systems. Lines of evidence show that the former is more active.

In the east Japan arc system a series of erogenic events started at the beginning of the Miocene. The trend of the Late Cenozoic erogenic belt is discordant with those of Mesozoic erogenic belts. The younger orogeny seems to be genetically independent of the older ones, although the older structures have given some effects on the younger ones in central Hokkaido and in south Fossa Magna. The east Japan arc system consists of the inner volcanic, outer geanticlinal and outermost subsiding trench belts. The inner and trench belts are regarded as forming a pair of high-temperature and low-temperature tectogenic belts. This pair may correspond to that of the Mesozoic erogenic belts as revealed by the study of metamorphic facies around the Pacific.

INTRODUCTION

During the last ten years, since Ikebe (1956) compiled the Cenozoic history of Japan, and Minato et al. (1956) summarized Tertiary history of east Japan from the viewpoint of structural geology of the island arcs, the studies of the Late Cenozoic geology and the geophysical features of Japan have been much advanced by many Japanese scientists. Based on these studies, the main geologic events during the Late Cenozoic in Japan are summarized here and the island arc features are discussed as an expres- sion of a recent erogenic activity, considering a regular.pattern of regional metamorphism in the circum-Pacific older erogenic belts.

This paper is the second report on the Late Cenozoic orogeny in Japan, the first one being mainly concerned with volcanic materials (Sugimura et al., 1963).

In preparation of this paper, the authors are indebted to many excellent reports concerning geology of the Japanese islands, including those by petroleum geologists (Hashimoto, 1962) and recent synthesis of the geology

Tectonophysics, 4(4-6) (1967) 349-366 349

::*@?

b

Fig.1. Island arcs in Japan. Pair of stippled and vertically hatched areas = Late Cenozoic erogenic belts; horizontally hatched area = Meeozoic- Tertiary geosynclinal belts; H = Hidaka erogenic belt; S = Shimanto Belt.

350 Tectonophysics, 4 (4-6) (1967) 349-366

of Japan (Minato et al., 1965), especially to geologic sheet maps of 1:50,000 and other scales published from the Geological Survey of Japan.

NEOTECTONIC DIVISION OF THE JAPANESE ISLANDS

The Japanese islands consist of’ several island arcs (Fig.1). They are grouped into two island arc systems; the east Japan island arc system and the west Japan island arc system.

The east Japan arc system shows not only a distinct zonal arrangement in distribution of deep-seated earthquakes, gravity anomalies, volcanoes, nature of volcanic rocks, are topography (Sugimura, 1960) and terrestrial heat flows (Uyeda and Horai, 19641, but also a series of tectonic movements in Late Cenozoic time, which would be regarded as erogenic processes.

The west Japan arc system, on the other hand, is less active in general than the east Japan system. Particularly, the fundamental arc-structure of the southwest Honshu Arc had been constructed before the Miocene, and zonal arrangement of geophysical phenomena such as that observed in northeast Honshu Arc is less distinctly recognized at present. The southwest Honshu Arc would be older than the northeast Honshu Arc.

The northeast Honshu Arc is divided into three tectonic provinces; the inner volcanic belts, the outer non-volcanic geanticlinal belt, and the outer- most subsiding trench belt.

The volcanic and oil field region, or the so-called green tuff region” onthe Japan sea side, belongs to the inner belt, and the Kitakami-Abukuma region on the Pacific side belongs to the outer belt. The third belt lies off Honshu, including the Japan Trench.

The east Japan arc system obliquely crosses the older erogenic belts. In the central part of Hokkaido, the east Japan arc system intersects the Hidaka erogenic belt which is similar in age to the Alpine orogeny in Europe. In the south Fossa Magna region of central Japan, the inner belt of the east Japan arc system superimposes upon the Shimanto Belt, which is an outer geosynclinal belt of Mesozoic to Paleogene orogeny in southwest Japan. In the above two regions, the structure of Late Cenozoic formations is more or less controlled by the older orogeny.

OUTLINE OF NEOGENE SEDIMENTARY HISTORY OF HONSHU

During Early Tertiary time, most of the Japanese islands had been subjected to subaerial denudation, However, two geosynclinal belts, the Hidaka Belt (Hunahashi, 195’7) in central Hokkaido and the Shimanto Belt on the Pacific side of southwest Japan, have existed since Mesozoic time.

Toward the beginning of the Miocene, the Japan Sea side area of Honshu became suddenly a region of violent volcanism followed by regional subsidence. The subsidence culminated during Middle Miocene, Afterwards, the sea has gradually retreated in general.

Fig.3 is a schematic diagram showing sedimentary history of the north- east Honshu Arc. Deposition in the inner belt started in the Early Miocene on basement rocks of Paleozoic formations and Late Mesozoic granites, with the accumulation of volcanic material, mainly of andesite and dacite of

Tectonophysics, 4 (4-6) (1967) 349-366 351

NEOOENE ANO 1

QUATERNARY ROCKS

m MOOENE ORANIlE

PRE-NEOEENE

PK- - S&lh , Fosra Maw G

* *cc

352 Tectonaphyeics, 4 (4-6) (1967). 349-366

alkaline, high-alumina basalt and tholeiite series (Ozawa, 1963; Miyagi, 1964), which were laid down partly on land and partly under sea water. These volcanics were covered by marine, rather uniform, oil-producing mudstone of the Middle Miocene age. The volcanism of basalt and dolerite was characteristic in this stage, along with acidic volcanism.

After the extensive deposition of marine mudstone in the Middle Miocene, differentiation into a few rising zones and downwarping basins began. The trend of arrangement of these zones and basins is parallel to the present northeast Honshu Arc. The sinking basins became narrower towards the end of the Miocene. In Pliocene time, they were separated into several intermontane, lacustrine basins (Kitamura, 1959; Ikebe, 1962). These basins and intervenient mountains correspond well, in situation, to the present-day basin and range topography in northeastern Honshu.

Accompanying the differentiation of the basins in the inner belt, granitic intrusions occurred in upwarping areas, The areas of marine sedimentation still remained in Pliocene but were restricted along the present coast.

In contrast to the inner belt, the outer belt of the same arc, the Kitakami and Abukuma Mountains, have kept a rising tendency with block movements during the Late Cenozoic (Chinzei, 1966).

The southwest Honshu Arc, on the other hand, has been less mobile in general, but there are structural provinces arranged parallel to the trend of the southwest Honshu Arc (Cenozoic Research Group of southwest Japan, 1960). The Japan Sea coast area (Hokuriku-San’in area) is similar in Miocene history to the inner belt of the northeast Honshu Arc in having Early Mio- cene violent volcanism and the succeeding marine invasion (Matsumoto and Wadatsumi, 1959; Kaseno et al., 1961; Sakamoto, 19661, whereas the Pacific- side belt (Nankai area) was entirely different in tectonic condition from the outer (Pacific-side) belt of the northeast Honshu Arc. The Nankai area had still been subsiding in Early Miocene as well as in Early Tertiary times, as a part of the Shimanto geosyncline. The median belt (Setouchi area) of the southwest Honshu Arc (Huzita, 2962) was the area of depression in Miocene and again in Pliocene, where thin shallow-sea deposits (Miocene) and lacustrine deposits (Pliocene) were formed. Since Pliocene, upwarping and block movement in meridional trend have become remarkable over the east- west trend of Miocene movements.

Fig.4 is a summary of chronological change of marine invasion (the third column), volcanic activity (the fourth column), and assumed intensity of crustal deformation (the fifth column) in the Japanese islands. The figure suggests some interrelationship between tectogenesis and volcanism.

TECTONIC DEFORMATION SINCE MIOCENE

Fig.5 shows the distribution of vertical displacement since the begin- ning of the Miocene. The total amount of vertical displacement of the ground surface is assumed to be represented by the present height of basal uncon- formity of marine Miocene deposits. For upheaved areas where the Miocene deposits were either completely eroded out or, not deposited, the amount was estimated from the altitude of nearby mountains capped by the Miocene deposits or from the data on Quaternary tectonic movement (Hatori et al., 1964).

Tectonophysics, 4 (&S) (1967) 349-366 353

EUROPEAN

STANDARD

PLEISTOCENE

7 PLEISANCIAN

PONTIAN

1 SARMATIAN

VINDOBONIAN

BURDIGALIAN

AQUITANIAN

I t-

W

INN

ER

B

EL

T

STANDARD

OGA

AKITA

OF

N.E. HONSHU

PENINSULA

OILFIELD

I

KATANISHI

SHIBIKAWA

.-----

WAXIMOTO

I

------

KITAURA

.------

FUNAKAYA

ONNAGAWA

m--

-w_

NISHIKUROSAWA

DAISHIMA

---_

DEWA

YOXOlE

5l.l

i5U

KITAKAMI

OU

TE

R

BE

LT

E

-

KITAKAMI

MOUNTAINS

7;

BASIC VOLCANIC

ROCKS

VI

CONGLOMERATE

NON-\1ARIM

t'I.ASTi-c DEF'O~ II'

Y""

ACIDIC VOLCANIC

ROCKS

g

SA

ND

ST

ON

E

SILTSTONE

I

MARINE DEPOSITS

SILICEOUS

SHALE

Subsidence prevails in the inner belt of east Japan, where the depth of the Miocene base attains more than 5,000 m in some basins.

The trend of individual basins in the belt, however, is diagonal to the arc.

Most of the central zone of the Hidaka erogenic belt and the outer belt of the northeast Honshu Arc belong to the area of upheaval. Southwestern Japan shows a relatively uniform tendency of uplift, but local displacement is fairly remarkable as described by Huzita (1962). The mountains in central Japan are inferred to have uplifted 2,000 m or more in amount.

Neogene rocks, even Quaternary rocks in places, are folded to various degrees. Fig.6 shows distribution of the general trend of fold axes. One linear mark indicates the average direction obtained from fold structures with wavelength about several kilometers in a sheetmap area of about 24 X 19 km2. The smaller map in Fig.6 shows folded zones of Japan and their gen- eral trend. Generally, these directions of folding are parallel to the trend of the present arcs (Fig.lf, but are not concordant with those of older rocks except in central Hokkaido and in south Fossa Magna (Mats&a, 1962), where the trend of Late Cenozoic folds is nearly parallel to the older belts and the Early Miocene rocks are folded together with Paleogene and older rocks.

Fig.7 shows the distribution of the degree of deformation since Miocene times, calculated from geologic sections mostly of the scale 1:50,000. Here, the degree of deformation is defined as a sum of the vertical component of folded strata and of the throws of faulting, CAH, divided by a length L, of the geologic section. Contour lines were drawn, based on the weighted means of degree of deformation obtained from the adjacent three or four points. Through this process, local high values partly due to a shorter L, less than about 10 km, are levelled. One of highly deformed zones lies in the Japan sea-side area of Honshu and Fossa Magna of the inner belts of the east Japan arc system. Another zone in Hokkaido is nearly parallel to Hidaka erogenic belt and is thought mainly to be the product of the late stage of the Hidaka orogeny.

Most foldings in the folded zones of east Japan are still active. This is indicated by folded Quaternary strata, folded river terraces and by precise re-levelling (Otuka, 1941; Sugimura, 1952).

A folded zone running along the Pacific coast of southwest Japan is older and is not active, There, the non-folded post-Early Miocene deposits cover the folded Miocene and earlier strata, forming gentle broad half-basin structures.

On the basis of previously obtained data about the time rate of deforma- tion for the past 10’ years, the age of commencement is inferred by some active deformation observed at the places shown in Fig.8. Here, the last high sea level (Shimosueyoshi stage) is assumed to be about 9.10* years ago. The known rates used here are of the order of 0.1-9.5 km/105 years for vertical and horizontal displacements and 1 o-2o/1O5 years for folding and tilting. If the rate of deformation is taken as constant during recent geologic time, the deformation in the areas mentioned should have started one to a few million years ago f Fig.8) (Sugimura, in press).

Fig.3. Stratigraphic columns of sedimentary basins in the northeast Honshu Arc (Chinzei, 1967). Numerals in columns indicate thickness in meters.

Tectonophysics, 4 (4-6) (1967) 349-366 355

PIEISTOCENE I KATAN'ISHI 1

I

SHIBIKAWA

- PLIOCENE IUmKTWOTO!

KITAURA

10 - l----i FUNAKAWA

ONNAGAWA I

20 -

NISHIKUROSAWA

VOLCANIC ROCK I

04krn3/rn? 3

Y

A , 'X

I ,

after ifter

A KITAMURA SUGIMURA (1959) et aL

x IKEBE 11962)

(1963:

l MINATO et al.

)EFO~TI~

INCREASINc

- RATJ

Fig.4. Ratio of emerged area to invaded area for northeast Honshu, volcanic material erupted on main islands and inferred rate of deformation in the stages since Miocene.

356 Tectonophysic5,4 (4-6) (1967) 349-366

e /

+ loaom

i._. 0 g&“- y,,,

- -3000

- -5000

Fig.5, Distribution of vertical displacement since the Miocene. The smaller map indicates the points where the heights of ~n~~~~rrn~~y were estimated,

Tectonophysics, 4 {4--6) (1967) 349-366 357

141* c

i

-f- 32%

l34O

ZOOKM O-

Fig.6. Trend of fold of Neogene rocks. Hatched areas are pre-Neogene rocks.

358 Tectonophysics, 4 (4-6) (196’7) 349-366

I4 2"

i

,4b0

/

I I ^_

_--

42. _--- - 2

!

i

0 ZOOKM

El

- 0.6 e

- 0.8 (I

- 1.0 a

Fig.7. Degree of deformation since the Miocene; smaller map shows general distribution of highly deformed area.

Tccronophysics. 4 (4 -6) (Iy6i) 34% 366 359

pzI@c)oS Of UmmwHI A

Fig.8. Inferred durattion of deformation under the assumption of con- stant rate. A. Verticaland horizontal movements. B.Tflting due tofolding in east Japan. Horisontal lines indicate the amount of observed or possible maximum displacement at each area. Oblique lines show the constant time rages of respective deformation estimated for recent geologic time (within 10” years). The cross points of the horizontal and the oblique lines indicate the inferred age of beginning of the deformation in respective area - after: Sugimura and Matsuda (1965) for the Atera fault; Sugimura and l&ruse (1865) for Nozima-zaki; Yoshikawa et al. f 1964) for Muroto-zalci; Matsuda (1986) for the Atotsugawa fault; Nakamura et al. (1965) for Awashima; Nakamura (1957) for Ojiya; Sugimura (1967, in press) for Ogurd.

Activation of tectonism since Late Pliocene is actually pointed out in some areas (Huzita, 1962; Chinzei, 1966; Matsuda, 1966). These suggest that the neotectonic movement in Japan might have been accelerated since Late Pliocene as compared with that in Miocene (Fig.4). This suggestion is a problem to be examined further.

360 Tectonophysics, 4 (4-6) (1367) 349-366

0.1 10nr

I PERfODS OF DURATION

B

Fig.BB (Legend see p. 360).

ISLANDARC FEATURESANDOROGENY

Schematic cross section across the northern part of the northeast Honshu Arc is illustrated in Fig.9, and the characteristic features of geology are compared between the inner, the outer and the trench belts of the arc (Table I).

The trench belt of the arc is characterized by strong negative gravity anomalies, low heat-flow values and high mantle seismicity. The belt has subsided during Late Cenozoic, particularly since Late Pliocene (Iijima and Kagami, 1961). The active tectonic state of the belt is also suggested by thick young sediments and young faulting (Ludwig et al., 1966).

The outer belt corresponds to the non-volcanic outer arc of the double arc (Umbgrove, 1947). The outer belt of northeast Honshu Arc consists mostly of metamorphosed Paleozoic rocks and Mesozoic granite and sedimentaries. This belt has been rather stable and has slowly uplifted throughout Cenozoic time. Raised peneplains are present. Late Cenozoic sediments are scarce and remain unfolded, dipping gently toward the sea. Volcanism is essentially absent during Cenozoic time.

The inner volcanic belt, on the contrary, has been the region of violent volcanism and rapid sedimentation in late Cenozoic time. History of events

Tectonophysics, 4 (4-6) (1967) 34S-366 361

/ 0 2OOkm

Fig.9. A schematic profile across the northern part of the northeast Honshu Arc. HF = heat flow (Uyeda and Horai, 19641, G = gravity (Bouguer anomaly for land, Tsuboi et al., 1956; free air anomaly for sea, recalculated by Sugimura, 19601, T = topography, E = foci of mantle earthquakes.

TABLE I

Characteristic geologic features of the inner, outer and trench belts of the east Japan arc system

Inner belt Outer belt Trench belt

Intermediate to acidic essentially no volcanism with granitic volcanism intrusion

Local vertical movements resulting in basins and mountains

gentle, continuous upwarping

regional subsidence and accumulation of sediments, particularly since Pliocene

Moderate folding

Alteration or metamorphism, producing: zeolite, chlorite, epidote albite etc., in volcanic rocks.

no regional folding

probable strong folding and faulting

possible regional metamorphism of high- pressure, low-temperature tvoe

362 Tectonophysics, 4 (4-6) (1967) 349-366

and structural trend are not inherited ones from the older orogeny, but are thought to be originated at the beginning of Miocene. This belt is composed of oil-bearing, moderately folded sedimentary basins and volcano-capped upraised ranges. Acidic to intermediate volcanism has repeatedly occurred since Miocene. Granitic plutons are associated with them (Fig.2). Miocene volcanic rocks often show a greenish appearance, due to alteration products

such as epidote, chlorite and other clay minerals (so-called “green tuff”). Mineral assemblages of zeolite facies and those similar to greenschist facies are present in the inner belt of the arc (Yoshimura, 1961; Utada, 1965; Shimazu and Sato, 1966), The metamorphic series from the zeolite facies to greenschist facies through the pumpellyite-prehnite metagraywacke facies, has been found in this belt from the South Fossa Magna region (Sakamoto et al., 1964; Matsuda and Kuriyagawa, 1965), where the Shimanto Belt extends across the inner belt of the east Japan arc system.

The problem whether or not the east Japan Arc system can be regarded as a modern erogenic belt independent of the older one, is discussed as fol- lows:

The Cenozoic events in Japan had been taken as post-erogenic disturb- ances following the Mesozoic orogeny. In 1956, however, Minato et al. com- pared the whole Late Cenozoic history of the inner belt of east Japan arc system with a life of an orthogeosyncline which had the initial, syn-erogenic, and final volcanisms in terms of Stille (1940). Two years later, Sugimura (1958) stated that recent-tectonic activities in the east Japan arc system in- cluding the outermost trench belt were probably the expression of a new orogeny started in the Miocene. In 1961, Miyashiro (1961a,b) suggested a possibility that the trench belt and the inner belt along the island arc cor- respond to the present-day metamorphic belts of high-pressure, low- temperature type and low-pressure, high-temperature type, respectively. This idea was followed by Matsuda (1964) in his review of the tectonic state of the Japanese islands and further supported by Takeuchi and Uyeda (1965) who examined the terrestrial heat flow data along the east Japan arc system. As stressed by Miyashiro (1961a), most of the Mesozoic erogenic belts in the circum-Pacific region have a pair of metamorphic belts of contrasted characters, viz. I0 the inner metamorphic belt” on the continental side, and “the outer metamorphic belt” on the oceanic side. The concept of a paired belt in metamorphic terrain can be extended to the erogenic belt in general, namely, the erogenic belt can be regarded as consisting of “the inner oro-

TABLE II

Contrasted features of paired erogenic belt

Inner erogenic belt

(Geosynclinal subsidence is not necessarily accompanied)

Intermediate to acidic magmatism (“syn-0rogenic and subsequent volcanism”)

Outer erogenic belt

geosynclinal subsidence and thick accumulation of sediments

basic and ultra-basic (ophiolitic) magmatism (“initial magmatism”)

High-temperature, low-pressure type metamorphism

strong deformation of sediments and regional metamorphism of high- pressure low-temperature type

Tectonophysics, 4 (4-6) (1967) 349-366 363

genie belt” and “the outer erogenic belt”. Essential features of the inner and the outer erogenic belts are summarized in Table II.

“Late Cenozoic orogeny , ” has not been fully accepted, because much at- tention has been paid only to the inner belt of the east Japan arc system, Indeed, the inner belt alone is not enough to be regarded as an erogenic belt. But, from the similarity to the Mesozoic orogeny in the Pacific region, it would be concluded that the Late Cenozoic island arc systems in Japan and also other active island arcs around the Pacific, probably represent new paired erogenic belts now in action.

The inner volcanic belt of the modern island arc would correspond to the inner erogenic belt, and the outermost subsiding trench belt would cor- respond to the outer erogenic belt of the circum-Pacific-type orogeny.(The outer geanticlinal belt of the island arc may have no corresponding belt in the Mesozoic erogenic belt, as in case of a single-arc type of the present island arc where the outer geanticlinal belt is absent)

ACKNOWLEDGEMENTS

The authors are much obliged to Prof. Tatsuro Matsumoto of the Kyushu University, who encouraged them to prepare this paper. Thanks are also due to Prof. Fuyuji Takai of the University of Tokyo, under whom this work was begun. The authors are very grateful to Dr. Kiyotaka Chinzei of the University of Tokyo, who always joined the constructive discussion and contributed much to this paper,

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Sugimura, A., 1958. MarianolrJaplrKamtschatka Orogen in TPtigkeit. Chikyu Kagaku. 37: 34-39 (in Japanese with German abstr.).

Sugimura, A., 1960. Zonal arrangement of some geophysical and petrological features in Japan and its environs. J. Fat. Sci., Univ. Tokyo, Sect.II, 12: 133-153.

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L. Krasny (U.S.S.R.): I am interested in the outermost trench belt. Is it the process of oceanization or

continentalisation? The fracture zone discovered by Udfnteev, several hundreds of kilometers to the east of the Kurile-northeast Japan Arc, may be the beginning of a future mobile belt. Do you think so?

T. Matsuda (Japan): The subsiding character of the outermost trench belt is thought to be an oro-

genie feature displayed only in the erogenic time. In the post-erogenic time after the subsidence, the belt would be upraised and exposed along the outside of the older continental crust as a granite-free eugeosynclinal belt similar to the Shimanto Belt of southwest Japan or the Franciscan Belt in California. This is not a procees of oceanization. Udintsev’s discovery is very interesting, but owing to my lack of know- ledge concerning it, I feel unable to discuss the tectonic meaning at present.

366 Tectonophysics, 4 (4-6) (1967) 349-366