MARINE GEOLOGY AND TECTONIC DEVELOPMENT OF THE BANDA SEA REGION, EASTERN INDONESIA:

SERI BENUA MARITIM INDONESIA DAN MUD VOLCANO

THE INDONESIAN MARITIME CONTINENT: 

MUD VOLCANO

UNIVERSITY OF CALIFORNIA

SANTA CRUZ

MARINE GEOLOGY AND TECTONIC DEVELOPMENT

OF THE BANDA SEA REGION, EASTERN INDONESIA:

A Model of an “Indo-Borderland” Marginal Basin

A Dissertation submitted in partial satisfaction of the Requirements for the degree of 

 DOCTOR OF PHILOSOPHY In EARTH SCIENCES

By  Hardi Prasetyo September 1988

Table of contents

TITLE PAGE

DEDICATION

ACKNOWLEDGEMENT

TABLE OF CONTENTS

LIST OF FIGURE AND TABLES

ABSTRACT

CHAPTER I

INTRODUCTION AND OVERVIEW OF THE PROBLEMS 

REPRESENTED BY THE “INDO-BORDERLAND”

BANDA MARGINAL SEA, EASTERN INDONESIA

1.     Marginal Basin

2.     Definition of the “Indo-Borderland” Marginal Sea

3.     Major Problems Related to the development of  the “Indo-Borderland”

4.     Hypothesis for the origin and development of the Banda Sea

5.     Scope of the study

CHAPTER II

TECTONIC AND SEDIMENTATION OF THE BANDA BASIN:

Geological consequence of trapped old oceanic crust 

behind a zone or arc-continent collision

1.     Introduction

2.     Geologic and Tectonic Framework of the Banda Basin

3.     Geophysical data and its interpretation

4.     Seismic reflection data and interpretation

5.     Structure and stratigraphic variation along the Banda Basin

6.     Near surface sedimentation processes

7.     Stratigraphy Model of Banda Basin

8.     Geohistory, Backstripping and Backtracking Analysis

9.     The Preset Tectonics

10.Tectonics and sedimentation history of the Banda Basin: Synthesis

11.The Geologic Significant of the Banda Basin Studies

CHAPTER III

MARINE GEOLOGY OF THE BANDA RIDGE:

Other evidence for displaced and submerged continental margin fragments within a marginal basin

1.     Introduction

2.     Previous survey of the Banda Ridges

3.     The Data Base

4.     General characteristics of the Banda Ridges

5.     Geological Domains

6.     Stratigraphic Framework and “Borderland Structural Styles” of The Banda Ridges

7.     Summary and Discussion

8.     Tectonic and Geologic History of the Banda Ridge: Implication for tectonic transition from “Borderland” to “Himalayan” styles

9.     Conclusions

CHAPTER IV

GEOHISTORY ANALISIS AND SUBSIDENCE HISTORY 

OF THE MISOOL, BURU, AND SUMBA TERRANES: an comparison to the Northwest Australia passive continental margin

1.     Introduction

2.     Geohistory and Backstripping Analysis

3.     Geohistory and subsidence reconstruction of the rifted continental margin fragments, and modern NW Australia Starve Passive Continental Margin

4.     Tectonic implications

5.     Conclusions

  

CHAPTER V

STRUCTURE AND SEISMIC STRATIGRAPHIC FRAMEWORK OF THE SULA BASIN: Northern edge of the “Indo-Borderland”

1.     Introduction

2.     Regional tectonic setting  of the Sula Basin and  correlation to the surrounding terranes

3.     Structure and seismic stratigraphic framework

4.     The Surface sediment characteristics from piston cores

5.     Discussion and summaries

6.     Conclusions

REFERENCES

ABSTRACT OF DISSERTATION

Marine Geology and Tectonic Development

of the Banda Sea Region, Eastern Indonesia:

A model of an “ Indo-Borderland” Marginal Basin

By Hardi Prasetyo

       The origin of the Banda Sea region is critical to the tectonic development of eastern Indonesia. The purpose of this study is to synthesize the existing geological and geophysical data into a tectonic model of the Banda Sea region, as an example  of a marginal basin developed within an active arc-continent collision.

          The model is based on analyses of single channel seismic reflection profiles, 3.5 kHz bathymetry, SeaMARC II sonographs, marine gravity data, dredge and piston core samples, and geologic investigations of the surrounding islands of Misool, Sumba. Buton and Sawu.

          The Banda Sea region does not conform to the generally accepted origins of marginal basins; it is neither a young spreading basin or a trapped piece of oceanic crust. Instead, the Banda Sea region is composed of collage of  oceanic and continental fragment that were displaced from the northern Australian continental margin and trapped within the Banda basin, prior to 7 Ma.

          This marginal basin is called an “Indo-Borderland” type because of its structural similarity to the Southern California Borderland, and its composition, in part of trapped Indian Ocean crust.

          The dissertation begins with a general overview of marginal basin development and the Banda Sea region, in particular. The overview is followed by a description of the seismic stratigraphic framework and structural style of the Banda Basin, previously called as the South Banda Basin.

This new name is proposed in order to emphasize its unique tectonic development with respect on the Banda Ridges in the central Banda Sea regions, and the Sula Basin, which has been previously called the North Banda basin.

          The Banda basin consists of oceanic crust formed in the Wharton Basin, trapped to the north of the western Banda arc, and overprinted by young basinal volcanism. The seismic stratigraphy of the basin consists of two types, these are :

1)    a “basin floor” or “proto-Banda” type which is well- developed in the Damar basin, and 2) the “filled basin” type which is characteristic of the  Wetar basin. The “basin floor” type consist of 4 seismic units (Banda-1 through Banda-4). The two lower units (Banda-3 and Banda-4) are correlated to the Mesozoic to Miocene seismic units of the Wharton Basin. The upper two units of the Banda basin are more reflective than equivalent seismic units in the Wharton Basin and mark a change in sedimentation related to the isolation of the Banda basin. Four stage (pre-Miocene) during which the oceanic basement was continuous with that of the eastern Indian Ocean;

2)    an “early-Banda” stage (7-19 Ma) which is marked by the formation of the intraoceanic Banda arc system and resulting isolation of the Banda basin;

3)    a “mature-Banda” stage (5 Ma?) during which the basin was faulted against southern margin of the Banda Ridges; and finally,

4)    a subsidence and deformation along the southern margin of the Wetar Basin in response to the collision of Australia, as well as basinal volcanism of unknown origin.

          The northern margin of the Banda basin is bounded by the Banda Ridges which consist of two groups (Lucipara and Sinta), each exhibiting a NE-trending Lucipara Basin, which is characterized by NW to NNW-trending abyssal hills, orthogonal to the fabric of the Banda Ridge.

          Dredge samples indicate that the acoustic basement of the ridges is composed of metasediments of continental origin, continental margin sedimentary rocks, and Miocene volcanic rocks.

          The basement is overlain by up to 200 m of pre-Upper Miocene to Recent pelagic strata that drapes the ridge. The similarity of the lithologic assemblage to the rocks exposed on the surrounding island suggests a common origin, that being continental slivers transported along strike-slip faults from Irian Jaya.

          In contrast, the Lucipara basin exhibits a thin cover of pelagic sediment, greater water depth, and higher heat flow, possibly indicating an origin of young oceanic crust or rifted (thinned) continental crust generated in a wrench environment, prior to Pliocene time.

 Small, elongated basins within the Banda Ridges are bounded by left-lateral (?) strike-slip faults, presently inactive. Recent deformation consists of thrust and compressional features (diapirs), best developed along the southern margin of the ridge system and within the interior along structural troughs. The southern margin of the ridge system is defindd by a reactive tectonic contract with the oceanic basement of the Banda Basin along the Lucipara Fault zone.

          Based on the concept of terrane analysis, the oceanic basement of the Banda Basin is referred to as the Bandasian Terrane. Likewise, the continental slivers of the Banda Ridges are called the Banda Ridge Terrane, and the basement underlying the Sula Basin is denoted as the Sulasian Terrane.

          Geohistory and subsidence analyses of the Bandasian Terrane are compared to other terranes of apparent continental margin affinity in the region, including sequences exposed on the island of Misool, Buru, and Sumba, and the northwest Australian continental margin.

These analyses show that the Bandasian Terrane has undergone a similar subsidence history  as the oceanic basement underlying basin, but is presently ~ 500 m shallower. The subsidence histories of  the Buru and Misool terranes differ  from that of the northwest Australian margin, in that Triassic time was characterized by rapid subsidence of the Buru and Misool terranes, and the Paleogen was marked by uplift.

          The Subsidence history of the Banda Ridge Terrane is inferred to be similar to that of  Misool and Buru, because of the similarity of lithologies. Triassic subsidence of the Buru and Misool terranes, and apparently the Banda ridge  terrane is related to extensive rifting and crustal stretching during the formation of the northwest Australian margin. Paleogene uplift of these terranes coincides with the Irian Jaya orogen. These terranes exhibited complicated vertical movements in the Neogene, which are related to strike-slip faulting and displacement from Irian Jaya, and the development of the “Indo-Borderland” marginal basin.

          The Sula basin in the northwest regions of the Banda Sea is surrounded by continental fragments (e.g. Sinta Ridge, Buru Island). The lower seismic stratigraphy framework in the southern depression is similar to the region of the Damar basin. However, with available data it is difficult to justify whether the Sula Basin has same origin with the Banda Basin (Indian Ocean origin). The upper seismic unit in the Sula basin is continuous with the upper seismic unit of the Banda ridges (LR1), suggesting a similar sedimentation regime since late Miocene time.

          The relationship of the Sula Basin, Sula platform, and southwest Sulawesi margin is compared to the tectonic framework of the Yakutat block, Kula plate, and southeast Alaska margin.

          The South Sula-Sorong fault is a strike-slip fault, responsible for displacing the Sula Platform to the west during the Neogene. This fault has been inactive since Pliocene. The juxtaposition of the Sula Platform and the Sula Basin was followed by the northwest movement of these fragments, in association with the development of the Tolo thrust along the northwest margin of the Sula basin. The Tampomas Ridges in the Sula basin may also be composed of fragments of continental affinity.

          In summary, Banda Sea region is composed of an Indo-Borderland marginal basin which is characterized by a collage of continental and oceanic fragment.

The continental fragments were initially displaced to the west-northwest along strike-slip faults, and subsequently modified by north-south compression associated with the active collision between the Banda arc and the Australian continent.