Three-Dimensional Architecture and Paleoenvironments of Osaka Bay

by Yasuto Itoh

This publication shows the three-dimensional configuration of the gigantic tectonic sag of the Osaka Bay sedimentary basin on the eastern Eurasian margin based on reflection seismic data never before published. The basin has developed relatively quickly since the dawn of the Quaternary. High-resolution subsurface images on the profiles provide highly valuable information about the architecture of active faults, paleoenvironmental changes, and mass balance on the convergent margin. The book presents an excellent case study of a tectonically controlled basin because morphologies and evolutionary processes of such basins show an enormous diversity, reflecting spatiotemporal variation in tectonic stress. Furthermore, this volume provides insight into the general mechanism of sedimentary basin formation.

The quantitative analyses contained here will be thought-provoking for industry experts, academics, and graduate and undergraduate students engaged in geologic survey and civil engineering. The contents will be especially useful to professionals in the fields of Quaternary geology, neotectonics, and active fault research.

Yasuto Itoh was awarded his M.Sc. and Ph.D. in geophysics from Kyoto University and now is a professor in the Graduate School of Science of Osaka Prefecture University. He conducts research into tectonics, stratigraphy, paleomagnetism, and geophysical/geochemical modeling of convergent margins, and has published more than 100 papers in the field of back-arc opening processes, the deformation mode of active plate margins, quantitative assessment of active faults, the paleoenvironment of East Asia, and the mechanism of sedimentary basin formation. His professional memberships include the American Geophysical Union, the American Association of Petroleum Geologists, the Japan Geoscience Union, and the Japanese Association for Petroleum Technology. He is also a member of the Integrated Research Project for Active Tectonics of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Keiji Takemura received a Ph.D. in geological science at Kyoto University. He now is a professor at the Institute for Geothermal Sciences, Kyoto University. He conducts research into stratigraphy, active tectonics, tephrochronology, and geothermal sciences, and has published more than 300 papers (half of them in English) in the field of Quaternary sciences of active faults, paleogeography, and the tectonic history of southwest Japan, environmental changes from lake and bay sediments, geothermal geology, soil engineering, and geoarchaeology. His professional memberships include the American Geophysical Union, the Japan Geoscience Union, the Japanese Association for Quaternary Sciences, and the Geological Society of Japan. He is also a leader of one of the programs of the Integrated Research Project for Active Fault Systems of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Preface

Acknowledgements

Chapter 1 Tectonic context of the study area

1.1 Plate tectonic framework of the eastern Eurasian margin

1.1.1 Chronicle of plate motions since 100 Ma

1.1.2 Present-day configuration

1.2 Tectonic epochs of southwest Japan - Previous studies

1.2.1 Paleomagnetism

1.2.2 Reflection seismic survey

1.3 Recent crustal movements revealed by geodetic observation

1.4 Spatiotemporal overview of the Osaka sedimentary basin

1.4.1 Paleogeography

1.4.2 Active faults on land

1.4.2.1 Geomorphological achievements

1.4.2.2 Tectonic significance of the "Kinki Triangle"

1.4.3 Geophysical studies

1.4.3.1 Gravity anomaly and gravity gradient tensor

1.4.3.2 Volumetric analysis

1.4.3.3 Numerical modeling of basin formation

Reference list

Chapter 2 Basic knowledge - Stratigraphy of the Osaka Group

2.1 Overview of sedimentary basins

2.2 Chronology

2.2.1 Biostratigraphy

2.2.2 Magnetostratigraphy

2.2.3 Tephrochronology

2.3 Paleoenvironment

2.4 Deep boring survey

2.4.1 Onshore data

2.4.2 Offshore data

2.5 Tectonic movements deduced from burial history

2.5.1 Isotope stage boundaries

2.5.2 Subsurface datum levels

2.5.3 Differential subsidence of northern Osaka basin

Reference list

Chapter 3 Reflection seismic data

3.1 Dataset

3.2 Correlation between subsurface datum planes and seismic horizons

3.3 Systematic descriptions

3.3.1 Data acquired by Geological Survey of Japan, AIST

3.3.1.1 Line GS-2M

3.3.1.2 Line GS-5M

3.3.1.3 Line GS-7

3.3.1.4 Line GS-8ME

3.3.1.5 Line GS-11

3.3.1.6 Line GS-12

3.3.2 Data acquired by Hydrographic and Oceanographic Department, JCG

3.3.2.1 Line HD-1

3.3.2.2 Line HD-2

3.3.2.3 Line HD-3

3.3.2.4 Line HD-4

3.3.2.5 Line HD-5

3.3.2.6 Line HD-6

3.3.2.7 Line HD-7

3.3.3 Data acquired by Hyogo Prefecture

3.3.3.1 Line HG-1-1M

3.3.3.2 Line HG-1-2M

3.3.3.3 Line HG-4-2M

3.3.4 Data acquired by Osaka Soil Test Laboratory, GRI

3.3.4.1 Line OD-A

3.3.4.2 Line OD-B

3.3.4.3 Line OD-C

3.3.5 Auxiliary data

3.4 Results

3.4.1 Structural architecture

3.4.2 Basin accommodation

Reference list

Chapter 4 Discussion - Origin and evolution of the Osaka basin

4.1 Comparison between proximal and peripheral parts of the basin

4.2 Marine-land connectivity of major structural trends

4.2.1 Awaji-Rokko Fault System and Osaka Bay Fault

4.2.2 N-S warping zones

4.2.3 Median Tectonic Line

4.2.4 Broad contractional horsts off the eastern coast of Awaji Island

4.3 Evolutionary process of the Osaka basin - a tectonic model

4.3.1 A synthesis of the Plio-Pleistocene tectonic events

4.3.2 Structural framework of the present Osaka basin

Reference list