Long-Term Surface Uplift History of the Active Banda Arc- Continent Collision: Depth and Age Analysis of Foraminifera from Rote and Savu Islands, Indonesia

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Theses and Dissertations

2005-07-06

Nova Roosmawati Brigham Young University - Provo

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BYU ScholarsArchive Citation Roosmawati, Nova, "Long-Term Surface Uplift History of the Active Banda Arc-Continent Collision: Depth and Age Analysis of Foraminifera from Rote and Savu Islands, Indonesia" (2005). Theses and Dissertations. 559. https://scholarsarchive.byu.edu/etd/559

This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. LONG-TERM SURFACE UPLIFT HISTORY OF THE ACTIVE BANDA ARC-CONTINENT

COLLISION: DEPTH AND AGE ANALYSIS OF FORAMINIFERA FROM ROTE AND

SAVU ISLANDS, INDONESIA

Nova Roosmawati

A thesis submitted to the faculty of

Brigham Young University

in partial fulfillment of the requirements for the degree of

Master of Science

Department of Geology

Brigham Young University

June 2005 BRIGHAM YOUNG UNIVERSITY

GRADUATE COMMITTEE APPROVAL

of a thesis submitted by

Nova Roosmawati

This thesis has been read by each member of the following graduate committee and by majority vote has been found to be satisfactory.

______Date Ronald A. Harris, Chair

______Date Scott M. Ritter

______Date Brooks B. Britt

BRIGHAM YOUNG UNIVERSITY

As chair of candidate’s graduate committee, I have read the thesis of Nova Roosmawati in its final form and have found out that (1) its format, citations, and bibliographical style are consistent and acceptable and fulfill university and department style requirements; (2) its illustrative materials including figures, tables, and charts are in place; and (3) the final manuscript is satisfactory to the graduate committee and is ready for submission to the university library.

______Date Ronald A. Harris Chair, Graduate Committee

Accepted for the Department ______Bart J. Kowallis Graduate Coordinator

Accepted for the College ______G. Rex Bryce Associate Dean, College of Physical and Mathematical Sciences

ABSTRACT

LONG-TERM SURFACE UPLIFT HISTORY OF THE ACTIVE BANDA ARC-

CONTINENT COLLISION: DEPTH AND AGE ANALYSIS OF FORAMINIFERA

FROM ROTE AND SAVU ISLANDS, INDONESIA

Nova Roosmawati

Department of Geology

Master of Science

Analysis of foraminifera for synorogenic pelagic units of Rote and Savu Islands,

Indonesia, reveals high rates of surface uplift in the past 1.5 Ma of the incipient Banda arc-continent collision. Paleodepth estimates are derived from benthonic forams and ages from planktonic forams. But estimates are complicated, however, by abundant reworking; yet several distinctive species have been found.

Synorogenic deposits in western Rote yield forams of biozone Neogene (N) 18 and depths from 5000-5700 meters at the base of the section, and 3600 meters at the top of the section. Eastern Rote yields forams of N 19/20 - N 22 and depths from 5400-5700 meters. Central Rote yields N 21 and depths from 5000-5700 meters. Because all of the sections are presently about the same elevation (~200 m), long-term surface uplift rates are slightly higher (1.84-3.29 m/yr) in eastern and central Rote than those in western

iv Rote. Forams from Savu yield ages of N19/20 - N 22. Across Savu depth estimates range from 3200-5700 meters, which yields a range of uplift rates from 1.86 mm/yr in SE Savu to 3.25 mm/yr in Central Savu.

These results indicate the Banda arc-continent collision caused uplift of Rote and

Savu at rates of 1-2 mm/yr over the past 3 Ma.

v ACKNOWLEDGEMENTS

The following thesis, while an individual work, benefited from the insights and

direction of several people. First, I would like to thank Brigham Young University and

the Geology Department for their financial support through the Specific Country Focus

Scholarship. Thanks also go to the University of Pembangunan Nasional “Veteran”

Yogyakarta for allowing me to complete my Masters degree.

In addition, a special thanks to my thesis chairman, Dr. Ronald A. Harris who

provided timely and instructive comments and evaluation at every stage of the thesis

process, allowed me to complete this project on schedule. Next, I wish to thank the complete Thesis committee: Dr. Scott M. Ritter, Dr. Brook B. Britt, and Dr. Wade E.

Miller. Each individual provided insights that guided and challenged my thinking, substantially improving the finished product. Additional thanks to Dr. R. Mark Leckie at the University of Massachusetts-Amherst, Dr. Kenneth L. Finger at University of

California Museum of Paleontology, and Dr. David Haig at the University of Western

Australia for assisting me on my foraminifera.

In addition to the technical and instrumental assistance above, I received equally important assistance from family and friends. Kris Mortenson, Marge Morgan, and Kim

Sullivan for the technical support that made it possible for me to finish my degree. My husband, Hendro Nugroho, provided on-going support throughout the thesis process, as

vi well as technical assistance critical for completing the project in a timely manner. My family, mom and dad, Bruce and Joanne Brook, Sean and Alicia Coyne, instilled in me the desire and skills to obtain the Master’s. I’d like to thank my fellow graduate students for the support and friendship they provided over the years. Finally, I wish to thank the respondents of my study (who remain anonymous for confidentiality purposes). Their comments and insights created an informative and interesting project with opportunities for future work.

vii TABLE OF CONTENTS

ABSTRACT...... iv

ACKNOWLEDGMENT...... iv

TABLE OF CONTENTS...... vii

LIST OF TABLES...... ix

LIST OF FIGURES...... x

LIST OF APPENDICES...... xi

INTRODUCTION...... 1

Previous works...... 3

Synorogenic Deposit of Timor Region………...... 5

STRATIGRAPHY OF ROTE AND SAVU ISLANDS...... 7

FORAMINIFERA ANALYSIS...... 9

Plankton Analysis...... 11

Benthic Analysis...... 12

Reworked fossils...... 13

UPLIFT RATES...... 13

CONCLUSION...... 14

REFERENCES CITED...... 15

Tables...... 20

Figures...... 23

Appendices...... 34

Appendix A...... 35

iv Appendix B...... 99

Appendix C...... 105

Appendix D...... 107

v LIST OF TABLES

Table 1: Sample locations for synorogenic units in Rote and Savu Islands…..…...…. 20

Table 2: Ranges of uplift rate estimates calculated for Rote and Savu Island ………. 21

vi LIST OF FIGURES

Figure 1: Tectonic map of Banda arc………………………………………………… 22

Figure 2: Map of geologic features of the Western Banda Orogen………………...… 23

Figure 3: Lithologic units of Rote Island…………………………………………..… 24

Figure 4: Serial sections through Timor, Rote, and Savu Islands………………….… 25

Figure 5: Geologic map of Rote………………………..………………………..…… 26

Figure 6: SEM images of characteristic Late Neogene planktonic foraminifera from 27

Rote and Savu Islands …………………………………………...…...…….

Figure 7: SEM images of characteristic deep benthic foraminifera from Rote and 28

Savu …………………………………………………………..……….……

Figure 8: Geohistory diagram of Rote and Savu Islands…………….……………...... 29

Figure 9: Model of progressive uplift from east to west.…………………………….. 30

Figure 10: Diagram of Batu Putih distribution from East Timor to Sumba…...……... 31

vii LIST OF APPENDICES

Appendix A: Foraminifera Analysis………………….………………...….……..…. 32

Appendix B: Stratigraphic Section of Batu Putih in Rote Island…………….……… 96

Appendix C: Number of species based on random fossils picked up…….…..…...… 103

Appendix D: Ratio P/B………………………………………………...... …..……. 106

viii INTRODUCTION

The Banda arc region (Figure 1) is an evolving arc-continent collision at the intersection of the large Asian, Australian, and Pacific Plates (Hamilton, 1979). The convergent plate boundary between Southeast Asia and the Indian Ocean is marked by the Java Trench, which is the site of subduction of oceanic lithosphere beneath the Sunda arc. At the eastern end of the Java Trench the Australian continental margin is colliding obliquely with the Sunda arc.

This collision zone trends eastward and then makes a counterclockwise U-turn curve called the Banda arc. The Banda arc consists of two ridges from which rise many young islands. The inner ridge is the Miocene-Present Banda volcanic arc. The outer ridge is a collisional wedge that includes the islands of Sumba, Savu, Rote, and Timor

(Figure 1). The uplift history of these islands is the theme of this paper.

Rote and Savu Islands are the youngest expressions of the active, westward propagating Banda arc-continent collision zone. The geology of these islands was first explored by Brouwer (1922), who documented fossiliferous Permian, Triassic, Jurassic,

Cretaceous, Eocene, and Miocene sediments that correlate with units in Timor. Because of these similarities Rote and Savu are considered the western most part of the Timor collision zone, which consists mostly of accreted Australian continental margin. South of these islands is where the position of the plate boundary, defined to the west by the Java

Trench, becomes ambiguous. The ambiguity is manifest by transitional geological and geophysical features, including: the transition of the convex southward Java Trench to convex northward Timor Trough (Johnston and Bowin, 1980), broad patterns of seismicity (McCaffrey et al., 1985), distribution of strain along multiple plate boundary

1 segments (Silver et al., 1983; Harris, 1991), and systematic changes in the GPS velocity

field (Genrich et al., 1996; Nugroho et al., 2004). The GPS velocity field shows that

islands to the west of Rote move only slightly relative to the Asian plate, while islands to

the east of Rote move mostly with the Australian plate.

Previous work in the region reveals that strain is partitioned throughout the

collision zone (Harris, 1991; Synder et al., 1996). Many of the plate boundary segments

are marked by high Quaternary uplift rates at known plate boundary segments (Merritts et

al., 1998). The long-term uplift history of many islands in the collision zone, however, is

poorly constrained. Most of these islands are blanketed by thick Cenozoic deposits of

foram-rich synorogenic limestone. These deposits provide depth and age constraints

needed to reconstruct the uplift history at temporal scales of 105 to 106 years, which is the focus of this paper.

The investigation was focused on the synorogenic deposits on the islands of Rote and Savu, which are the closest islands to the traceable plate boundary. Little is known about the geological evolution of these islands, as they are mostly blanketed by coral terraces with underlying synorogenic deposits. Analysis of planktonic and benthonic foraminifera from these deposits provided essential age and depth of deposition constraints that document the rise of these islands from depths of several kilometers below sea level to there present elevation.

The aim of the study is to test how the Banda orogen propagates by comparing the uplift history of Rote and Savu Islands with islands to the east where similar biostratigraphic data already exist (Kenyon, 1974; Audley-Charles, 1989; Fortuin and De

Smet, 1991). Differences in the uplift history help constrain the position of plate

2 boundaries through time in the region. One of the main hypotheses is to test whether the islands show simultaneous uplift as suggested by Johnston and Bowin (1980), or progressive uplift from east to west as predicted by models for collisional propagation

(Harris, 1991).

Previous Work

Although geological investigations in the Timor region were initiated over 150 years ago, only a few studies have investigated uplift history based on micropaleontology. Audley-Charles (1989), who drew from the work of Kenyon (1974), determined rates of Neogene and Quaternary uplift in Timor Island using planktonic foraminifera. The dating of the onset of uplift of Timor, from a deep submarine position at the end of Neogene nappe emplacement, to mountains now reaching nearly 3 km high, indicates a long-term uplift rate initially of 3 mm/yr, which then slowed to about 1.5 mm/yr around 3-5 Ma ago.

The uplift history of central West Timor during the past 3 Ma was investigated by

De Smet et al., (1990). They used forams to determine chronostratigraphy and paleobathymetry from two sites in the Central Basin of Timor (Figure 2), which were uplifted in two relatively short episodes. At about 3.0 Ma ago, pelagic calcilutites accumulated slowly on top of a strongly deformed subsurface at a depth of about 1500 m.

The actual Central Basin did not yet exist and there were no nearby islands supplying clastic sediment. Rapid uplift of about 750 m occurred in the area between 2.2 to 2.0 Ma, associated with the origin of the Central Basin and emergence of parts of northern Timor.

Erosional products from the new land infilled the basin with up to 1.5 km of distal

3 turbidites. This event was followed by a long relatively quiet period during which

hemipelagic marls and turbidites accumulated at upper-middle bathyal depths. A second

period of fast uplift, which still may be in progress, started around 0.2 Ma ago and

resulted in emergence of large parts of the Central Basin. Estimated average rates of

uplift over the past 0.2 Ma varies from 5 to over 10 mm year (De Smet et al. 1990).

Fortuin et al., (1991) also investigated rates and magnitudes of late Cenozoic

vertical movements in the outer Banda arc islands of Buton, Buru, Seram, Kai, Tanimbar,

and Timor using a geohistory analysis technique. In most cases short periods of uplift as

high as 10 mm/yr alternate with longer intervals of tectonic rest or subsidence at

maximum rates of 0.2 mm/yr. Synorogenic deposits with a high time-stratigraphic

resolution show pulses of uplift with durations between 0.1 and 1 Ma, and rates

exceeding 5 mm/yr. Such movements are of similar frequency to eustatic third-order sea-

level changes, but an order of magnitude larger in vertical extent, and therefore most

likely control major unconformities.

Merritts et al., (1998) investigated surface uplift rates over time scales of 103-105 years using 230Th ages of emergent coral terraces from the islands west of Timor. Two

samples at Semau Island correspond to the 5a (c. 83 ka) sea-level highstand and a low

surface uplift rate of 0.2-0.3 mm/yr. Two samples from Rote Island yielded late Holocene

ages and an average short-term uplift rate of c. 1-1.5 mm/yr. A similar investigation by

Chappell and Veeh (1978) indicate that surface uplift rates along the northeast coast of

East Timor are 0.5 mm/yr, which decrease westward to 0.03 mm/yr near Central Timor.

Jouannic et al., (1988) measured uplift rates near Kupang of 0.3 mm/yr. Coral terraces in

eastern Sumba yield an uplift rate of 0.5 mm/yr (Pirazzoli et al., 1991).

4 Previous studies throughout the Banda arc region indicate that vertical movement

in this region started about 5 Ma in Timor region (Audley-Charles, 1989). Uplift rates are

greatest near the present forearc and retroarc deformation fronts which are now north and

west of Timor (Merritts et al., 1998). GPS measurements also indicate that rates of

horizontal movement with respect to Asia increase eastward due to increased coupling

with the Australian plate (Genrich et al., 1996; Nugroho et al., 2004). These data reveal

how the collision, which initiated in Timor region, has broadened and propagated

westward.

Synorogenic Deposit of Timor Region

Subduction initiated adjacent to Timor region about 15 Ma ago, corresponding in

age with the oldest volcanic units in the arc (Abbott and Chamalaun, 1981). A small

accretionary wedge, like the one currently forming the Lombok ridge astride the Java

Trench, formed in front of the new arc complex, remnants of which are found in Savu

(Vorkink et al., 2004), Rote (Figure 4 and 5), and Timor (Harris et al., 1998). Deep

marine deposits blanketed the accretionary wedge slope as it expanded to the south. The

transition from subduction to collision initiated a change in facies in these deposits from

deep marine chalk to turbidites. As the forearc ridge emerged to form the various islands

that make up the outer Banda arc it was covered with coral terraces and fluvial deposits.

These deposits are collectively known as the Viqueque Formation of Audley-Charles

(1968), which was later elevated to the Viqueque Group, with each of the distinct facies as formations (Figures 3).

5 The basal unit of Viqueque Group is known as the Batu Putih Formation, which is the Indonesian word for white rock (Figures 3 and 5). It consists of white chalk and marl with abundant foraminifera. It is ubiquitous throughout the islands in Timor region. The first turbidite bed overlying the chalk marks the boundary with the Noele Marl

Formation, which is found throughout the Central and Viqueque Basins of Timor. The

Noele Marl Formation shows strong lithologic variations, which consists of marl and calcareous claystone, tuffaceous marl and tuffaceous calcilutite, silty and sandy limestones that become more clastic-rich and coarsen upwards. These deposits are overlain by the Ainaro Gravel Formation and Baucau Coral limestone Formation of

Audley-Charles (1968).

In Rote, the Batu Putih Formation is found in discontinuous patches along the southern coast. Thicknesses vary from 37-50 meters in the west to 237 meters in the eastern part of the island (Figure 5).

In Savu, the Batu Putih Formation is found mostly in the eastern part of the island where sections up to 100 m thick are exposed (Vorkink and Harris, 2004).

Unconformably overlying the Batu Putih Formation in both Rote and Savu are coral terrace deposits. In Savu, conglomerates are also found locally (Vorkink and Harris,

2004).

The Noele Marl Formation, which is a product of turbidite deposition and found throughout Timor sitting on top of Batu Putih Formation, is absent in Rote and Savu. The source of the Noele Marl in Timor was from nearby islands to the north, which do not exist in Rote and Savu. In fact, these islands are a modern analog for the conditions that

6 existed much earlier in Timor during the deposition of the Noele Marl Formation

(Kenyon, 1974).

STRATIGRAPHY OF ROTE AND SAVU ISLANDS

Unconformably underlying the synorogenic deposits of Savu, Rote, and Timor is

an emergent orogenic wedge, from the collision of the Banda arc with the Australian

continental margin. The orogenic wedge consists mostly of a thrust stack of units ranging in age from Early Permian to Quaternary (Brouwer, 1922).

Three major lithotectonic units are identified (Harris, 1991) (Figure 3). The Banda

Sea Terrane is a piece of the forearc that forms a structural backstop against and under which the Australian continental margin units are stacked. The Australian units consist of two main groups. The Kolbano Sequence which represents a sedimentary succession deposited on the Australian passive continental margin after it formed (Charlton, 1991) and the Gondwana Sequence, representing the pre-breakup sedimentary cover of

Gondwana. Synorogenic deposits unconformably overlie these units and consist of the

Bobonaro Melange and the Viqueque Group (Audley-Charles, 1968).

Brouwer (1922) was the first to report the geology of Rote Island. He found mostly sedimentary rock from Permian to Miocene ages. The base material is Permian limestone with alkalic basalt. Triassic and Jurassic strata consist mostly of fossiliferous shale and sandstone and subordinate marl and limestone. The Upper Cretaceous consists of chert, red limestone, and conglomerate. Eocene material consists of nummulitic limestone, which is intercalated with older rocks and Miocene material consists of foraminiferal limestone.

7 A 1:250,000 geological map of Rote by Rosidi et al., (1979) shows that the

Triassic Aitutu Formation, which is part of the Gondwana Sequence, is the oldest unit exposed. Most of the rest of the island was interpreted by Rosidi et al., (1979) as mélange of the Bobonaro Complex and overlain by the Noele Marl Formation. The youngest exposures are corraline limestone and alluvium.

The field studies in Rote Island recognize five distinct lithotectonic units (Figure

5): 1) the Triassic Aitutu Formation, which is a white, occasionally pink, limestone with interbedded carbonate mudstones that vary from pale to grey to black color. This formation is only exposed along the north coast near Baa; 2) the Jurassic Wailuli

Formation, which is a homogenous dark grey and red colored claystone and shale with interbedded organic-rich limestone, calcilutite, siltstone, and ironstone. The Wailuli

Formation is exposed mostly in the core of Rote Island and was interpreted as mélange by Rosidi et al., (1979). The contact between the Wailuli and the Aitutu Formations is well exposed at Termanu (Figure 1); 3) the Cretaceous Nakfunu and Tertiary Ofu

Formation, which is part of the Kolbano Sequence, an Fe/Mn-rich shale and mudstone interlayered with radiolarian chert overlain by massive calcilutite layers that represent rise and slope deposits respectively of the Australian Continental Margin; 4) the Late

Miocene-Quaternary Batu Putih Formation, composed of white foram-rich chalk, is exposed in East and Central Timor, and yields an age range from Early to Late Pliocene

(N 18 – N 22). The depositional contact between the Batu Putih Formation and Wailuli in

Rote is unidentified; 5) Quaternary coralline limestone, which covers almost the entire island. Melange with blocks of Permian Maubisse Formation is found locally in zones of inactive mud diapirism.

8 A recent investigation of the structural evolution of Savu Island by Vorkink, et al.,

(2004) identified five tectonostratigraphic units: 1) Babulu Formation, which is part of

Gondwana Sequence, consisting of micaceous-rich sandstones, wood fragments in shale, and Halobia sp.-rich shale layers; 2) Wailuli Formation; 3) Nakfunu Formation; 4) Batu

Putih Formation; 5) melange-with blocks of Gondwana Sequence-sandstones, Permian crinoid-rich limestone, and metamorphic and igneous rocks are found in a stream valleys west of Seba.

FORAMINIFERA ANALYSIS

Each occurrence of the Batu Putih Formation was mapped, measured, and sampled throughout Rote and Savu Islands (Figure 5 and Table 1). Samples were collected at the base, middle, and top of each outcrop. The best exposed sections in Rote are found in Nasedanon Village (Western Rote), Bebalain Village (Central Rote), and

Tebole and Oeledo Village (East Rote). The base of the Batu Putih Formation is not exposed in many part of Timor region. However, the top of Batu Putih Formation is commonly found in Rote, Savu, and Sumba Islands, where it is much younger (N 22) than Timor (Figures 6 and 10). The bases of Batu Putih are progressively younger than in

Timor as one move westward from Rote to Savu. In Sumba, the Batu Putih Formation is correlative with the Waikabubak Formation, which is as old as Middle Miocene.

In order to establish the uplift history of Rote and Savu Islands both plankton and benthic forams were studied. Benthic forams provide paleodepth estimates and planktonic forams provide age estimates. Planktonic and benthonic foraminifera are

9 present in most samples and generally show good to excellent preservation. Only

foraminifera from recrystallized samples were difficult to analyze.

The early plankton classification was based on simple morphological criteria such

as the type and position of aperture, presence or absence of keels, shape of chambers, and

the basic coiling mode and other factors (Bolli et al,. 1957). More recent classification schemes emphasize phylogenetic classification that requires understanding of ancestor- descendant relationship between taxa and also morphological features that distinguish different lineages. The analysis employs the classification from Kennett and Srinivasan

(1983) and Bolli et al., (1985) who studied foraminifera in tropical region.

The planktonic zonal schemes were established based on the first evolutionary appearance of planktonic species. The Neogene is subdivided into twenty N zones from

N4 in the earliest Miocene to N 22 in the Late Quaternary. Neogene planktonic foraminiferal zonation for tropical regions follows Blow (1969) as emended by

Srinivasan and Kennett (1981) who subdivided N 17 into an N 17A and N 17B.

Benthic foraminifera remain one of the least known and understood groups of the microbenthos (Figure 7). In the Batu Putih Formation on Rote and Savu, benthic forams are well preserved in almost all of the samples. The benthic determination on this paper used the taxonomic classification criteria of van Markhoven et al., (1986) and Jones

(1994). The depth determination was based on benthic species which has deepest depth because the synorogenic on Rote and Savu Islands was deposited near Timor Trench.

Another method used to obtain paleobathymetric data is the plankton (P) to benthic (B) ratio (van Marle et al., 1987). Percentages of planktonic foraminifera were increased by intense vertical circulation. Area with intense vertical circulation are

10 characterized by an increase in surface productivity and caused enrichment of the

planktonic population. In addition, vertical circulation condition cause oxygen depletion

of the bottom water and may reduce the number of benthic foraminifera. The P/B ratio of

foraminifera in every sample was determined by examining 300 random individuals and

using the formula:

P / P + B x 100%

To obtain the depth (D), we transformed the formula to:

D = e (0.061· P + 1.25)

Plankton Analysis

The age of Batu Putih Formation in Rote and Savu was determined by using the

first appearance of the youngest species and the last appearance of older species. All sites sampled contain planktonic assemblages with characteristic late Neogene forms such as

Globorotalia tumida, Globorotalia plesiotumida, Neogloboquadrina altispira altispira,

Globorotalia tosaensis, Neogloboquadrina dutertrei, Pulleniatina primalis, Pulleniatina praecursor, Sphaeroidinella dehiscens, Candeina nitida, Globorotalia margaritae, and

Globorotalia merotumida (Figure 6).

The age of the lowest part of the section exposed in West Rote is bracketed by the first appearance of Globorotalia tumida tumida, and the last occurence of Globorotalia merotumida to resolve Zone of N 18 (5.1 Ma). In East Rote, the lowest part of the section is foram Zone N 19, based on the first appearance of Globorotalia crassaformis and the lastest appearance of Sphaeroidinellopsis kochi. Age for the top of the section in Tebole

11 is constrained by the first appearance of Globorotalia tosaensis and the last appearance of

Globigerinoides extremus which define Zone N 21 (2.1 Ma) and N 22 (0.7 Ma).

Benthic analysis

Benthic foraminifera are common and well preserved with the exception of those from the western section. Figure 7 illustrates most of the species found in Rote and Savu

Islands. The species, which are found in deep water (middle bathyal to lower abyssal) such as Oridorsalis umbonata, Cibicidoides wuellerstorfi, Pullenia bulloides,

Globocassidulina subglobosa, Melonis pompiliolides, Laticarinina pauperata, and

Uvigerina proboscidea, were found in all of the sections. Each assemblage is assigned a paleodepth range based on Van Morkhoven (1986).

The lowest part of the West Rote section yielded a range depth of 5000-5700 meters (Lower Abyssal Zone) based on Oolina truncata and Osangulariella umbonifera, while the upper part of this section yielded a range depth of 3600-5000 meters (Middle

Bathyal Zone) based on Pyrgo lucernula and Epistominella globularis. The East Rote section contains more benthic varieties and yielded deeper depth ranges than those in the

West Rote section. The lowest part of East Rote section yielded a depth range of 5400-

5700 meters (Lower Abyssal Zone) based on Globocassidulina subglobosa and

Oridorsalis umbonata. The upper part of this section yielded a depth range of 5000-5700 meters (Lower Abyssal Zone) based on Cibicidoides wuellerstorfi and Nonionina affinis.

The P/B ratio for most samples in Rote and Savu are 90-98% planktonic forams, which is consistent with water depths >2500 meters.

12 Reworked fossils

Age determinations used in this paper are based on the latest first appearance of youngest species and the last appearance of older species. Any species with last appearance prior to this determination is most likely from reworking. The reason using the youngest species is the current in Banda Arc Ocean is gateway between Pacific and

Indian Ocean which is able to transport original fossils and redeposited them (Reed et al.,

1987). The presence of Globorotalia archeomenardii, Globorotalia fohsi fohsi,

Globorotalia praemenardii, and Globigerinoides primordius, even though they have short age ranges, most likely represent reworked species. Another test of reworking is the relative abundance of various species (Van Marle, 1987). In most cases suspect species only accounted for < 5 % of the individuals in random counts. Almost all of the samples in the Rote and Savu sections have several reworked species. The source of these species is unkown, but similar forams are documented from the Sunda Shelf and Sumba (Effendi et al., 1985).

UPLIFT RATES

In order to obtain the long-term uplift rate of Rote and Savu Islands, a geohistory analysis technique introduced by van Hinte (1978) was employed. This approach uses the sum of the depth and present elevation data divided by the age. The results show that uplift rates in eastern Rote are higher than in western Rote (Table 2). The lowest part of the southeast Rote section yields an the uplift rate range of 1.13 mm/yr - 1.84 mm/yr while the upper part of this section yield an uplift rate range of 1.69 mm/yr - 3.29 mm/yr.

13 The range of uplift rates from the southwest Rote section is 0.98-1.19 mm/yr in the lowest part and 0.71-1.05 mm/yr in the upper part of the section (Figure 8).

The geohistory diagram from Savu Island yields similar calculated uplift rate ranges to those of Rote Island (Figure 8). The uplift rate range in Central Savu (1.86-3.25 mm/yr) is higher than in SE Savu (1.86-1.87 mm/yr). Uplift in both islands took place between 3 Ma to the present from initial depths of 5000 to 5700 meters.

The age of the top of Batu Putih Formation in East Timor is most upper Miocene

(N 18) to most lower Pliocene (N 19) (Audley-Charles, 1986), and becomes younger westward to Mid-Miocene (N 20) in the Central Basin of West Timor (De Smet, 1990).

The most-upper part of Batu Putih in Rote and Savu contains late Pliocene to Quaternary planktonic assemblages (N 21 to N 22).

These time-transgressive from East Timor to Rote and Savu indicate that the collision of the Outer Banda arc with the margin of the Australian continent is propagating west (Figures 9 and 10) at a rate of 104 km/Ma. This is consistent with estimates of 110 km/Ma based on the geometry of the oblique collision (Harris, 1991).

CONCLUSION

The results from the detailed examination of planktonic and benthonic forams in synorogenic deposits of Rote and Savu, and from previous work throughout Timor, indicate that uplift rates vary in time and space as the arc-continent collision propagates westward. The Batu Putih facies yield similar maximum ages throughout the Banda orogen, but its minimum age varies progressively along the orogenic strike. In East

Timor the Batu Putih was terminated at N 19 by deposition of turbidites shed from

14 emerging islands to the north. In West Timor the top of the Batu Putih Formation was deposited coincident N 20. The offshore portions of the islands of Rote and Savu are currently at the same stage as Timor was during N 20.

Foraminifera from the synorogenic deposits in western Rote yield older (N 18) and shallower (3600-5000 meters) conditions than the sections in East Rote, which yields forams of N 21 - N 22 and depths from 5000-5700 meters. The synorogenic section in

Central Savu has a younger age (N 21 – N 22) than the section in SE Savu.

These data indicate that the Banda arc-continent collision is propagating west and arrived in Rote and Savu within the past 1.8 Ma. This is the youngest age of the deep

(5000 meters) Batu Putih chalks now having an elevation of 237 meters above sea level.

The long-term surface uplift measurements using forams at a time scale of 106 years reveals similar result to uplift rate estimates using uplifted coral terraces, at time scales of

104-105 years.

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16 Genrich, J. F., Bock, Y., McCaffrey, R., Calais, E., Stevens, C. W., and Subarya, C., 1996, Acretion of the southern Banda arc to the Australian plate margin determined by Global Positioning System measurements, Tectonics, 15, 288-295.

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Harris, R.A., Kaiser, J., Hurford, A.J. and Carter, A., 2000. Thermal history of Australian passive margin sequences accreted to Timor during Late Neogene arc- continent collision, Indonesia, Journal of Asian Earth Sciences, V. 18, p. 47-69.

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Jones, R. W., 1994. The Challenger Foraminifera. Oxford University Press.

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Kennett, J. P., and Srinivasan, M. S., 1983. Neogene Planktonic Foraminifera: A Phylogenetic Atlas: Stroudsburg, PA (Hutchinson Ross).

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17 Merritts, D., Eby, R., Harris, R. A., Edwards, R. L., and Chang, H., 1998, Variable rates of Late Quaternary surface uplift along the Banda Arc-Australian plate collision zone, eastern Indonesia, In: Steward, I.S. & Vita-Finzi, C. (eds) Coastal Tectonics. Geological Society, London, Special Publication, 146, 213-224.

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19 Tables

20 Tabel 1. Sample locations for synorogenic units in Rote and Savu Islands

Sample Lat. Long. Elevation (m)

RT-002 10.5326 122.5624 37.5 RT-003 10.5339 122.5642 12.5 RT-004 10.5344 122.5644 10 RT-TX04 10.4853 123.110 130 RT-W03 10.507 122.5925 100 RT-027 10.500 122.5926 75 RT-029 10.5056 122.5829 65 RT-024 10.5048 122.5920 27 RT-X06 10.4837 123.525 177 RT-X05 10.4852 123.511 225 RT-X03 10.4845 123.522 200 RT-X02 10.490 123.439 150 RT-X01 10.4844 123.46 55 RT-V08 10.474 123.1325 225 RT-V09 10.472 123.1329 200 RT-Y08 10.4722 123.1332 198 RT-V05A 10.4714 123.1331 142 RT-V05C 10.4714 123.1331 137.5 RT-Y01 10.4739 123.1359 12.5 RT-U10 10.4222 123.1725 200 RT-U11 10.4139 123.1738 190 RT-U08 10.4130 123.1742 170 RT-U12 10.4213 123.1727 50 RT-U02 10.4141 123.1814 125 RT-040C 10.4143 123.1818 80 RT-040B 10.4143 123.1818 75 RT-040A 10.4143 123.1818 60 RT-U03 10.4147 123.1820 45

SV-62 10.5222 121.9665 107 SV-60 10.5282 121.9801 61 SV-67 10.5034 121.9055 146 SV-64 10.4981 121.9031 78 SV-71b 10.4579 121.8865 SV-71a 10.4579 121.8865 81 SV-72a 10.4493 121.885 23 SV-72c 10.4493 121.885

21 Table 2. Ranges of uplift rate estimates calculated for Rote and Savu Island

Elevation Depth Range (m) Age Range (Ma) Uplift Range (mm/yr) Section Location (m) above M.S.L Min. Max. Max. Min. Min. Max.

Section 1 Nuluhai, SW Rote 37.5 3600 5000 5.1 4.8 0.71 1.05 10 5000 5700 5.1 4.8 0.98 1.19

Section 2 Kokolo, Central Rote 130 3600 5700 4.8 3.9 0.77 1.49 27 5000 5700 5.1 4.8 0.98 1.19

Bebalain, Central Section 3 Rote 232 4300 5700 3.9 3.2 1.16 1.85 55 5200 5700 3.9 3.1 1.35 1.86

Section 4 Tebole, SE Rote 237.5 5000 5700 3.1 1.8 1.69 3.29 12.5 5400 5700 4.8 3.1 1.13 1.84

Nusaklain, East Section 5 Rote 200 3600 4450 3.9 3.1 0.97 1.44 50 5000 5700 3.9 3.1 1.29 1.85

Section 6 Oeledo, East Rote 125 3600 4200 3.9 3.1 0.95 1.39 45 5000 5700 3.9 3.1 1.29 1.85

Section 1 SE Savu 107 4400 5700 3.9 3.1 1.16 1.87 61 3200 5700 3.9 3.1 0.84 1.86

Section 2 Central Savu 146 4400 5700 3.1 1.8 1.47 3.25 78 4400 5700 3.9 3.1 1.15 1.86

22 Figures

23 115˚ 120˚ 125˚ 130˚ 135˚ -5˚ 2000 -5˚

Banda Sea 2000

4000 4000 4000 A r c a 2000 d A r c 4000 B a n 4000 Inner 2000 2000 d a B a n 2000 2000

5000 2000 Timor r Sumba ute O -10˚ 4000 -10˚ Rote Timor Trough Savu 5000 2000 4000 5000 2000 5000

Australian Plate

-15˚ -15˚ 115˚ 120˚ 125˚ 130˚ 135˚ Figure1. Tectonic map of Banda Arc. General physiography of Banda Arc with indication of 1000 m bathymetric contour, illustrating major structural elements, and relative plate motion. The black arrow represents the Australian plate motion with respect to the Banda Sea. Toothed lines indicate front of subduction zone. 24 Asian Plate

Wetar Thrust Flores Thrust Wetar

Alor Sumbawa Flores

Eastern Sunda Arc 123 E Discontinuity Timor 0.5 Viqueque Basin Sumba 0.3 Central Basin Semau Timor Trough Savu 1.0 Rote Indo-Australian Plate Java 1.5 Trench Transcurrent fault Oceanic Normal fault Crust Continental Crust Thrust fault Slope Shelf Active Volcanoes Reef Terrace Deposits Synorogenic Basins Accreted Material Figure 2. Map of geologic features of the Western Banda Orogen. Abrupt widening of the deformation zone occurs after underthrusting of the Australian passive continental edge. Synorogenic basins develop on the orogenic slope as the accretionary wedge widens. Underthrusting of the Australian shelf shortens the orogenic wedge and causes it rise above sea level where it begins to erode. Rote and Savu Islands occupy a transitional position between wedge widening and wedge narrowing; between wedge uplift without erosion and wedge shortening with erosion (Harris, et. al., 1998). Submarine structure modified

25 from Vanderwerff (1991). AUSTRALIAN CONTINENTAL MARGIN SYNOROGENIC UNITS UNITS

Quaternary Corals PLEIST. L E PLIOCENE LATE Batu Putih Formation VIQUEQUE GROUP MID MIOCENE E Bobonaro Melange

L with blocks of Maubisse Formation. Ofu Formation E OLIGOCENE L M E EOCENE L E PALEOCENE KOLBANO SEQUENCE LATE CRETACEOUS EARLY Nakfunu Fm. /Menu LITHOLOGIES BREAKUP UNCONFORMITY Carbonate

Claystone MIDDLE Sandstone

JURASSIC Chert EARLY Wailuli Fm. Wailuli + + + + + Igneous rocks

Marl LATE ~~~ Aitutu Fm. TRIASSIC MID GONDWANA SEQUENCE GONDWANA

Figure 3. Lithologic units of Rote Island. 26 NW 125˚ SE EAST TIMOR A. Magmatic Arc 0 A

B -20 -10˚ -10˚ 20 C CENTRAL TIMOR B. E gh Magmatic Arc rou or T D Tim 0

10- 125˚ -20 20 WEST TIMOR C. Magmatic Arc 0

AUSTRALIAN -20 SUNDA ARC CONTINENTAL MARGIN 20 ROTE D. Timor Trough Magmatic Arc 0 Permian-Triassic -20 20 Australian Continental Margin E. Savu Thrust Magmatic Arc SAVU Timor Trough 0

Australian Continental Crust ~ 30 km -20

Figure 4. Serial sections through Timor, Rote, and Savu Islands. The sections represent various stages of collisional deformation. The collision arrived at East Timor about 4-5 Ma, at West Timor and Rote and Savu Islands about 3-1 Ma. Lithotectonic units explanation: Black-forearc basement; Dark grey-Gondwana Sequence (pre-breakup) and melange; Diagonal stripes-Kolbano Sequence (post-breakup); White-synorogenic deposits. Redrawn from Harris (1991) and Harris et. al., (1998). 27 122º35' 45' 123º00' 15' 123º30' 10º25' 10º25'

1.0-1.3 Qa Alluvial Uplift rate (m/ky), previous study Teluk Makoe 1 Sample localities 30' 30' Ql Coralline Limestone Usipuka Lake

Selat Usu

QTn Batuputih Formation Kolbano sequence

Teluk Korobafo Teluk Papela Tb Wailuli Formation

TRa Aitutu Formation P. Batuhun 1.0-1.3 P. Rote 5 6

N 21- N 22

45' 45' P. Nuse

4 P. Ndau 3 P. Doo N 19/20 N 19 -

2 Tg. PondalaunN 19/20 Tg. Dombo 1.0-1.3 P. Lai N 21

1 N 19- P. Landu N 19/20

N 18 N 17- N 18 - N 18- N 19/20 N 19 P. Dana N 18 N 18 N 19 N 19 11º00' 1 2 3 4 5 6 11º00' 122º35' 45' 123º00' 15' 123º30' Figure 5. Geologic map of Rote. Major differences between this map and earlier versions published by Rosidi et. al., (1979) are: 1) most areas shown as melange were recognized as Wailuli Formation, and 2) areas mapped previously as Noele Marl were recognized as Batu Putih Formation. 28

Figure 6. SEM images of characteristic Late Neogene planktonic foraminifera from Rote and Savu Islands

Figure 7. SEM images of characteristic deep benthic foraminifera from Rote and Savu

30 MICROFAUNAL ANALYSIS OF SAMPLES Samples Measured section 177 5 PLANKTIC BENTHIC ORGANISMS FOR FORAMINIFERA BIOZONATION FOR PALEODEPTH

AGE IN MA BATHYMETHIC Meter HISTORY 3

2 OUTCROP DATA GEOHISTORY DIAGRAM

0 1

GEOHISTORY DIAGRAM OF SAVU GEOHISTORY DIAGRAM OF ROTE

Age (M a) Age (M a) 5.1 4.8 3.1 2.4 1.8 5.1 4.8 3.1 2.4 1.8 Elev (m) Elev (m)

300 300

200 3.29 mm/yr (max)-1.69 mm/yr (min) 200 3.25 mm/yr (max)-1.47 mm/yr (min) 100 100

sea level 0 sea level 0 Depth (m) Depth (m)

1.87 mm/yr (max)-1.16 mm/yr (min) 500 500 1.05 mm/yr (max)-0.71 mm/yr (min) 1.86 mm/yr (max)-0.84 mm/yr (min) 1000 1000 1.19 mm/yr (max)-0.98 mm/yr (min) 1.86 mm/yr (max)-1.15 mm/yr (min) 2000 1.84 mm/yr (max)-1.13 mm/yr (min) 2000

3000 3000

4000 4000

5000 5000

6000 6000

Figure 8. Geohistory diagram of Rote and Savu Islands. The maximum uplift rate in southeast Rote is higher (1.69 mm/yr-3.29 mm/yr) than those in southwest Rote, and the uplift rate in Central Savu is higher (1.47mm/yr-3.25 mm/yr) than those in southeast Savu.

31 (a)

New land

Timor Savu Basin Sumba 1000 3000 PRESENT 2000 4000

Savu Rote 5000 4000 Java Trench 5000

3000 Scott Plateau 5000 (b) 4000

N 22 (1.8 Ma) Turbidite now Savu Basin offshore of Rote 1000 2000 3000 4000 and Savu 5000 4000 Java Trench 5000

3000 Scott Plateau 5000

4000

(c)

Turbidite in N 20/21 east and west 1000 2000 3000 (3.6-3.1 Ma) 4000 Timor 5000 4000

5000

3000

(d)

N 19 Turbidite in 1000 3000 (3.6-4.8 Ma) 2000 4000 east Timor

5000 4000

5000 Java Trench

4000

(e)

No land N 18 (>4.8 Ma)

1000 3000 2000 4000

5000 4000

5000 Java Trench

4000

Figure 9. Model of progressive uplift from east to west. The model shows the horizontal movement of collision between Australian continent (dark grey band) and Java Trench. The collision caused uplift of Timor Island beginning about 4 Ma (dashed lines) and Rote and Savu Islands beginning about 3 Ma. Black area represent land, dots area represent turbidite, and shaded light grey represent zone of active volcanism. 32 AGE SUMBA EAST Foram SAVU ROTE WEST CENTRAL (Ma) Zone (Fortuin et. al. 1991) TIMOR TIMOR TIMOR Coral Terraces and 0.7 N23 Alluvial gravels NOELE MARL QUAT. FORMATION

N22 VIQUEQUE GROUP 1.8

N21 3.1 N20 3.25

PLIOCENE N19 4.8 N18 5.0 ? FORMATION BATU PUTIH N17

7.7

LATE MIOCENE LATE N16 10.0 ?

N15

FOLD-THRUST AUSTRALIAN CONTINENTAL MARGIN

AND MELANGE MIDDLE MIOCENNE MIDDLE

volcani- clastics 16.0

E.MIO. Oligocene BT

Figure 10. Diagram of Batu Putih distribution from East Timor to Sumba. Changes in lithofacies through time document propagation of collision to west. This depositional environment of the Batu Putih Formation in Savu and Rote is analogous to the earliest synorogenic deposits in Timor from near the onset of subduction to initial emergence of the accretionary wedge. The Batu Putih Formation in Rote, Savu, and Sumba is thicker than the Batu Putih in Timor and extends to N 22 (Harris, 1998).

33 Appendices

34 Appendix A: Foraminifera analysis

Sample: RT-002 Location: Nuluhai, SW Rote