1 Relative relative sea-level change in western New Guinea recorded by regional
2 biostratigraphic data
3 D. P. Gold1, L. T. White1,2, I. Gunawan1,3, M. BouDagher-Fadel4
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5 1. Southeast Asia Research Group, Department of Earth Sciences, Royal Holloway University
6 of London, Egham, Surrey, TW20 0EX
7 2. School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW,
8 Australia
9 3. Institut Teknologi Bandung, Jl. Ganesha No.10, Lb. Siliwangi, Coblong, Kota Bandung,
10 Jawa Barat 40132, Indonesia
11 4. Department of Earth Sciences, University College London, Gower Street, London, WC1E
12 6BT, UK
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1 27 Abstract
28 We present new biostratigraphic analyses of approximately 200 outcrop samples
29 across western New Guinea. These data were used to reconstruct palaeogeography
30 of the region from the Silurian to present day. Biostratigraphic ages and
31 palaeodepositional environments were interpreted from occurrences of planktonic
32 and larger benthic foraminifera, together with other fossils and environmental
33 indicators where possible. These data were compared with existing geological maps
34 and regional hydrocarbon well data to develop a more regional understanding of how
35 palaeoenvironments and palaeogeographies changed through time in western New
36 Guinea. Our analysis of these data identified two major transgressive-regressive
37 cycles in regional relative sea-level with peak heights occurring in the Late
38 Cretaceous and Late Miocene. During the Late Paleozoic and Early Mesozoic
39 terrestrial deposition was prevalent across much of western New Guinea as it formed
40 part of the northern promontory of the Australian continent. Relative sea-levels
41 increased during a regional transgressive event that occurred between the Late
42 Jurassic and the Late Cretaceous. This is particularly marked by widespread
43 carinate planktonic foraminifera found in sediments of this age in various outcrops
44 and wells across the region. Sea-levels dropped during a regressive event between
45 the Late Cretaceous and the Paleogene, resulting in the widespread development of
46 shallow water carbonate platforms by the Middle to Late Eocene. A minor
47 transgressive event occurred during the Oligocene, but this ceased in the Early
48 Miocene, due to the collision of the Australian continent with intra-Pacific island arcs.
49 This collision event resulted in widespread uplift, which is marked by a regional
50 unconformity. Carbonate deposition continued in platforms that developed in the
51 shallow seas until these were drowned during another transgressive event in the
2 52 Middle Miocene. This transgression reached its peak in the Late Miocene and was
53 followed by a further regression culminating in the present day topographic
54 expression of western New Guinea.
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56 Keywords: Tectonics; planktonic; larger benthic; foraminifera; paleogeography;
57 biogeography
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59 1. Introduction
60 New Guinea has represented the northernmost boundary of the Australian Plate
61 from the present until at least the Permian (perhaps as early as the Carboniferous),
62 when New Guinea was part of an Andean-style arc system that extended around a
63 large portion of Gondwana (Charlton, 2001; Hall 2002; 2012; Hill and Hall 2003;
64 Crowhurst et al., 2004; Metcalfe 1998; 2009; Gunawan et al., 2012; 2014; Webb and
65 White, 2016; Jost et al., submitted around xmas). This long-lived plate boundary
66 records evidence of numerous tectono-thermal events during the Paleozoic,
67 Mesozoic and Cenozoic (e.g. Visser and Hermes, 1962; Pieters et al., 1983; Davies
68 and Jaques 1984; Pigram and Davies 1987; Pigram and Symonds 1991; Baldwin
69 and Ireland 1995; Baldwin et al., 2004; 2012; Davies 2012; Bailly et al., 2009; Holm
70 et al., 2013; 2015; 2016). However, much of the geology of New Guinea is also
71 dominated by siliciclastic and carbonate deposition during seemingly long periods of
72 quiescence (Pieters et al., 1983; Pigram; Visser and Hermes, 1962; Fraser et al.,
73 1993; Hill, 1991; Davies, 2012; Baldwin et al., 2012). We focus on the age and
74 depositional environment of these sediments in western New Guinea, an area that is
75 relatively underexplored, with the last major geological mapping campaign being
76 conducted in the 1980’s (e.g. Masria et al., 1981; Pieters et al., 1983; Dow et al.,
3 77 1986; Atmawinata et al., 1989; Pieters et al., 1989; Dow et al., 1990; Harahap et al.,
78 1990; Pieters et al., 1990; Robinson et al., 1990; Panggabean et al., 1995). We
79 present new biostratigraphic age data based on benthic and planktonic foraminifera,
80 as well as facies analyses from nearly 200 outcrop samples from western New
81 Guinea. Where possible, we compared these results with publicly available
82 hydrocarbon well locations, biostratigraphic analyses and interpreted depositional
83 environments (e.g. Visser and Hermes, 1962; Fraser et al., 1993). The aim of this
84 work was to better establish the duration and facies distribution of strata to better
85 understand the spatio-temporal distribution of periods of queisence at the northern
86 margin of the Australian Plate between the Silurian and present day.
87
88 1.1 Geological mapping of western New Guinea
89 The first comprehensive geological mapping of Indonesian New Guinea was
90 conducted between 1935 and 1960 by geologists of the Nederlandsche Nieuw
91 Guinee Petroleum Maatschappij. The results of this work are compiled and
92 summarised in Visser and Hermes (1962). The observations that are reported in this
93 work lay the foundation for the stratigraphy of Irian Jaya and remain highly relevant,
94 despite this work being completed before the advent of plate tectonics. The
95 stratigraphy and tectonic development of western New Guinea was refined by
96 Indonesian and Australian government geologists between 1978 and 1982; the
97 results of which are summarised in Pieters et al. (1983).
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99 1.2 The Bird’s Head, Neck, Body and Tail
100 New Guinea is often described to reflect the shape of a bird, comprising the Bird’s
101 Head, Neck, Body, and Tail from west to east, respectively (Fig. 1). The Bird’s Head
4 102 and Neck, and part of the Body are within the Indonesian provinces of West Papua
103 and Papua (formerly known as Irian Jaya). The rest of the Bird’s Body and the Tail
104 are found in Papua New Guinea. The island’s peculiar morphology largely reflects
105 the geology and tectonic evolution of the island. For example, the Bird’s Neck is
106 largely composed of limestones and siliciclastic rocks shortened during the
107 development of the Lengguru Fold and Thrust Belt (e.g. Bailly et al., 2009; Francois
108 et al., in press - Lithos)(Fig.1). These deformed rocks form part of a mountain belt
109 that extends from eastern New Guinea (the Bird's Head), along the Central Range
110 (the Bird’s Body) to the eastern tip of the island (Bird’s Tail) (Fig. 1). Rocks to the
111 south of New Guinea are primarily of Australian continental affinity whereas those to
112 the north consist of ophiolite and island arc volcanics of Pacific Plate provenance.
113 These two domains are separated by a central, complex region of juxtaposed fault
114 slices of sediments together with variably metamorphosed and granitic rocks,
115 marking the suture (Fig. 1) formed during arc-continent collision in the Early
116 Miocene, (e.g. Pieters et al., 1983; Milsom, 1992). Thus the stratigraphy of the Bird’s
117 Head can be broadly described as intra-Pacific island arc material to the north and
118 east, which accreted to Australian continental material to the south and west. The
119 post-collisional stratigraphy of both domains is reasonably contiguous (Fig. 2).
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121 We report data from strata that were deposited on the northern margin of the
122 Australian continent from the Silurian to present, together with strata from the
123 accreted intra-Pacific island arc(s), focussing primarily on the stratigraphic and
124 palaeogeographic evolution of the Bird’s Head and Neck, together with the western
125 part of the Body.
126
5 127 2. Depositional History of western New Guinea sediments
128 2.1 Australian Plate stratigraphy
129 The distribution of outcropping strata mapped by Masria et al., (1981); Pieters et al.
130 (1983); Dow et al. (1986); Atmawinata et al. (1989); Pieters et al. (1989); Dow et al.
131 (1990); Harahap et al. (1990); Pieters et al. (1990); Robinson et al. (1990);
132 Panggabean et al. (1995) used in this study are depicted in Figure 3. The oldest
133 strata within the Bird’s Head consist of variably metamorphosed siliciclastic rocks
134 considered to be derived from rocks to the south (i.e. Australian craton). These have
135 poor age control, but were assigned a Silurian-Devonian age from several graptolites
136 and because these rocks are cross-cut by Carboniferous and Permian intrusions
137 (Visser and Hermes, 1962; Pieters et al., 1983). These sequences are known as the
138 Kemum and Aisasjur Formations (Fig. 3) and are considered to represent distal and
139 proximal turbidite deposits, respectively (Visser and Hermes, 1962; Pieters et al.,
140 1983). There are no other rocks of this age exposed in western New Guinea,
141 however, these may be equivalent to the XXX found in Papua New Guinea, and are
142 potentially equivalent to the widespread deposition of Ordovician turbidite sequences
143 across much of eastern Australia (e.g. Fergusson?; Peacock?).
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145 The oldest carbonate unit in western New Guinea is the Modio Dolomite of the
146 Central Ranges (Fig. 3), deposited during the Silurian-Devonian (Fig. 2; Pieters et
147 al., 1983). During the Carboniferous, a phase of volcanism is recorded by K-Ar data
148 (Jost et al., XXXX – IPA 2017?), this was followed by approximately 100 My of
149 volcanic quiescence before further volcanism during the Triassic. The Carboniferous
150 to Permian was a period of relatively stable paralic sediment deposition, with
151 occasional shallow marine incursions marked by thin limestone beds in New
6 152 Guinea’s Central Range. The Permo-Carboniferous Aifam Group (Fig. 3) contains
153 various terrestrial and marine deposits (Visser and Hermes 1962, Chevallier &
154 Bordenave 1986, Dow et al., 1988). In this group the Aimau, Ainim and Aiduna
155 formations are reported to contain conglomerates, red beds and coal seams
156 suggesting a terrestrially influenced, possibly deltaic and lacustrine, depositional
157 setting (Norvick et al., 2003), the Aifat mudstone however may have been deposited
158 in a basinal setting (Pieters et al., 1983).
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160 During the Triassic a second phase of volcanism is recorded by the presence of
161 granitoids in the Netoni Intrusive Complex (Webb and White, 2016), Anggi Granite,
162 Wariki Granodiorite, Warjori Granite, Central Range (Crowhurst, XXXX) and detrital
163 zircons within the Tipuma Formation derived from ash fall tuff (Gunawan et al., 2012;
164 2014). The only sedimentary rocks known from the Bird’s Head are arid terrestrial
165 deposits of the Tipuma Formation (Fig. 3), some of which interpreted to have been
166 deposited as fluvial run off from a volcanic arc (Gunawan et al., 2012; 2014) with the
167 nearest known carbonates of this age found in the Late Triassic Manusela and
168 Asinepe Limestone formations of Misool and Seram (Pieters et al., 1983; Martini et
169 al., 2004). Here, early to mid Jurassic calcareous sediments were deposited in
170 shallow seas with little siliciclastic input. In the Bird’s Head, deposition of siliciclastic
171 material forming the Tamrau Formation and Kembelangan Group (Fig. 3) correlated
172 to the shelfal deposits of the Demu and Lelintu Formations of Misool (Hasibuan,
173 1990), persisted throughout the Jurassic and into the Late Cretaceous (Fig. 2). On
174 Misool
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7 176 The Cretaceous siliciclastic units of the Kembelangan Group include the Jass
177 Formation, Piniya Mudstone and the Woniwogi and Ekmai Sandstones (Fig. 3).
178 Carbonate deposits in the Bird’s Head are not known until the Late Cretaceous
179 (Pieters et al., 1983) where Coniacian to Maastrichtian age siliciclastics of the Ekmai
180 Sandstone pass laterally into the deep-water pelagic carbonates of the Simora
181 Formation (Fig. 2; Brash et al., 1991). Fragments of inoceramid bivalves within the
182 base of the conformably overlying Waripi Formation suggest a Late Cretaceous age.
183
184 From the Late Cretaceous and into the Paleogene there is a distinct change from
185 siliciclastic to carbonate deposition recorded across the Bird’s Head. Visser and
186 Hermes (1962) proposed the ‘New Guinea Limestone Group’ (NGLG) to include Late
187 Cretaceous to Middle Miocene limestones, between 1km and 1.6km thick, which
188 outcrop in the western Bird’s Head, through the Lengguru Fold and Thrust Belt, into
189 the Central Range and Papua New Guinea (Brash et al., 1991; Fig. 3). The oldest
190 Paleogene strata of the NGLG, the Waripi Formation, were deposited in shallow-
191 water areas of a new Cenozoic basin from the Mid to Late Paleocene (Brash et al.,
192 1991; Fig. 2). In deep-water areas to the north of this basin, turbidites of the Daram
193 Formation (Norvick et al., 2003) were deposited. Brash et al. (1991) suggest that in
194 these deep-water areas the Imskin Limestone may interfinger with the Waripi
195 Formation (Fig. 2). The Cenozoic basin was relatively stable throughout the Eocene,
196 depositing the shallow-water Faumai and Lengguru Limestones, while the Imskin
197 Limestone continued accumulating pelagic carbonate up until collision with the intra-
198 Pacific island arc in the Early Miocene (Figs. 2 and 3).
199
8 200 2.1 Pacific Plate and contiguous stratigraphy
201 Within the intra-Pacific island arc, carbonate deposition was restricted to patch reefs
202 developed around eroded volcanoes known from the Eocene age Auwewa
203 Formation (Fig. 2), up until a phase of collision in the Early Miocene (Wilson, 2002).
204 Following collision, carbonate platform development was widespread across much of
205 the Bird’s Head. Early to Middle Miocene platform carbonates of the Kais and Maruni
206 Limestones, and Wainukendi and Wafordori Formations (Figs. 2 and 3), were
207 subsequently drowned during a Mid to Late Miocene transgressive event that
208 terminated platform accumulation abruptly (Brash et al., 1991; Gold et al., in review).
209 During the Pliocene, or very latest Miocene, rapid uplift attributed to major thrusting,
210 folding (Wilson, 2002) and strike-slip faulting prevailed in the Bird’s Head causing the
211 formation of several basins (Pieters et al., 1983). Erosion of uplifted areas filled
212 these basins with much siliciclastic sediment. Only the islands of Misool and Biak
213 remained starved of siliciclastic sedimentation permitting deposition of platform
214 carbonates of the Wardo, Korem and Mokmer Formations (Fig. 2) in relatively clear
215 waters (Pieters et al., 1983; Wilson, 2002).
216
217 3. Methodology
218 This paper presents the results of several field campaigns conducted by the
219 Southeast Asia Research Group (SEARG), Royal Holloway, University of London, in
220 the Bird’s Head of Indonesian New Guinea. Over these campaigns nearly 200
221 samples were collected of the New Guinea Limestone and associated carbonate
222 units. These include a mixture of spot samples as well as samples from logged
223 stratigraphic sections. All samples were thin sectioned and examined for petrography
224 and biostratigraphic dating using planktonic and larger benthic foraminifera, of these,
9 225 198 samples yielded well-constrained biostratigraphic ages. Ages are assigned
226 using planktonic foraminiferal zones of Blow (1979), Berggren and Miller (1988) and
227 Berggren et al. (1995), recalibrated to Wade et al.’s (2010) sub-tropical planktonic
228 foraminiferal zones. Larger benthic foraminiferal zones are assigned to the Indo-
229 Pacific ‘letter stages’ of Adams (1965, 1970). We subdivided the biostratigraphic
230 results into 20 time intervals to show the palaeogeographic evolution of western New
231 Guinea between the Silurian and Pleistocene.
232
233 Palaeogeographic reconstructions were determined using bathymetric preferences
234 of organisms (Hallock and Glenn, 1986; van Gorsel, 1988; Murray, 2006;
235 BouDagher-Fadel, 2008; 2015; Beavington-Penney and Racey, 2004; Lunt, 2013)
236 observed in each sample. These preferences are summarised in Figure 4. Our
237 palaeogeographic maps are subdivided into five relative bathymetries according to
238 the bathymetric preferences (Fig. 4) assigned to samples with depth-diagnostic
239 foraminiferal assemblages. Where heterogeneous depositional environments were
240 interpreted at a single locality, the modal depositional setting for that time and
241 location is recorded in the gross depositional maps.
242
243 In addition to the new analyses of samples collected across the Bird’s Head, we
244 present our reinterpretations of biostratigraphic, wireline log, stratigraphic columns,
245 palaeogeographies and palaeoenvironmental interpretations from public domain data
246 from 150 exploration wells (Fig. 5) and regional stratigraphy of individual reef
247 complexes within the Salawati and Bintuni basins (Table 1). Stratigraphic intervals
248 within the wells were assigned to the relative bathymetry scheme using records of
249 foraminiferal occurrences that meet the criteria laid out in Figure 4.
10 250
251 Palaeogeographic maps were constructed from the new analyses of outcrop and
252 well data and synthesis of regional facies distributions collated from the public
253 domain. The depositional bathymetries of samples and well intervals interpreted for
254 each time slice were plotted using ArcGIS so that the spatial distribution of facies
255 could be compared with existing palaeogeographic maps of the region (Visser and
256 Hermes, 1962; Audley-Charles, 1965; 1966; Vincelette, 1973; Redmond and
257 Koesoemadinata, 1976; Collins and Qureshi, 1977; Gibson-Robinson and Soedirdja,
258 1986; Brash et al., 1991; Norvick et al., 2003; Golonka, 2006; 2009). The new
259 palaeogeographic maps were overlain on the present day configuration of western
260 New Guinea (e.g. Visser and Hermes, 1962; Audley-Charles, 1965; 1966; Gibson-
261 Robinson and Soedirdja, 1986; Brash et al., 1991) as the position of New Guinea
262 relative to Australia has not changed much since Permian (Audley-Charles, 1965;
263 1966; Gunawan et al., 2012; 2014). Consequently we do not attempt the palinspastic
264 restoration of structural features, such as the displacement of faults or large-scale
265 rotation of crustal fragments (e.g. Norvick et al., 2003; Golonka et al., 2006; 2009,
266 Charlton, 2010; Hall, 2012). While these maps are somewhat simplified in terms of
267 the region’s tectonic history, our aim was to produce a series of maps that could be
268 used to identify the present day distribution of potential hydrocarbon plays and as an
269 independent means to assess periodicity of localised tectonic driven
270 uplift/subsidence events compared to global changes in sea level.
271
272 A regional relative sea-level curve for Western New Guinea throughout the
273 Phanerozoic was produced by calculating the average bathymetry of all points
274 analysed within a specific time periods. For a given time period the range, maximum,
11 275 minimum and average bathymetry was calculated so that an a modal relative sea-
276 level curve for Western New Guinea could be calculated. Error bars were included to
277 highlight the range of bathymetries within the time period. This regional relative sea-
278 level curve could then be compared to global sea-level curves (e.g. Haq and Al-
279 Qahtani, 2005; Müller et al., 2008; Snedden and Liu, 2010) to assess potential timing
280 of tectonic events.
281
282 4. Results and discussion of palaeogeographic reconstructions 283
284 The following sections present both the results of the palaeogeographic
285 reconstructions and discussion of how these maps compare to previously published
286 work from similar studies.
287
288 4.1 Silurian
289 During the Silurian, bathymetries in excess of 100m are interpreted across much of
290 the Bird’s Head and Neck, shallowing towards the south-east (Fig. 6A). This
291 interpretation is based on published descriptions and distribution of the widespread
292 basement block comprising the Kemum Formation. Two wells reviewed by this study
293 penetrated Silurian material, no new analyses of outcrop samples of this age were
294 undertaken in this study.
295 Water depths greater than 100m are interpreted based on the presence of
296 graptolites including Monograptus turriculatus and M. marri (Visser and Hermes,
297 1962), typical of Silurian deep-water settings, found within the Kemum Formation.
298 This formation is described to contain sedimentary structures typical of distal
299 turbidites and the Aisasjur Formation, which outcrops at the western extent of the
12 300 Kemum basement block, is reported to comprise proximal turbidite deposits (Pieters
301 et al., 1983). This suggests the presence of localised north-east directed bathymetric
302 gradient and transport direction for turbiditic material in the central Bird’s Head (Fig.
303 6A). The prevalence of deep water settings in western New Guinea during the
304 Silurian supports Golonka et al.’s (2006) interpretation that large areas in the
305 Gondwana were submerged at this time.
306 A broad south-easterly shallowing trend towards the Bird’s Body is interpreted (Fig.
307 6A). This is based on the presence of the Modio Dolomite to the east of the Bird’s
308 Neck and encountered within the Cross Catalina-1 well farther to the east in the
309 Bird’s Body, and presence of late Silurian limestones containing the tabulate coral
310 Halysites spp. in the Central Ranges (Fig. 6A; Visser and Hermes, 1962). We
311 interpret the Modio Dolomite to have a shallow-water carbonate-rich protolith,
312 relative to the deeper water sediments to the north-west.
313 4.2 Devonian
314 The south-east directed shallowing trend continued into the Devonian where
315 bathymetries in excess of 100m are interpreted in the Bird’s Head and Neck (Fig.
316 6B). This interpretation is based on published descriptions and distribution of the
317 Kemum and Aisasjur Formations in the north-west. Two wells reviewed by this study
318 penetrated Devonian material, confirming the presence of shallow water facies to the
319 south-east of the study area. The expansion of moderate water facies, between 20m
320 and 50m depth, in the south-east compared to the Silurian is due to an increased
321 number of data points. These additional data points incorporated reinterpretation of
322 Devonian age outcrop samples collected in the Central Range, reported by Visser
323 and Hermes (1962).
13 324 Visser and Hermes (1962) report Devonian age micaceous sandstones and impure
325 limestones found within river pebbles in the Central Ranges. These rocks contain a
326 fossil assemblage that contains gastropods, scaphopods, bivalves, brachiopods,
327 including Spirifer spp., and tabulate corals including Favosites spp. and Heliolites
328 spp. These assemblages and rock types are indicative of shallow marine photic zone
329 and neritic depositional settings, reflected in our palaeobathymetric reconstruction
330 (Fig. 6B). South-east directed shallowing may continue south into Australia,
331 supporting the Golonka et al. (2006) model of shallow marine siliciclastics and
332 carbonates across much of Papua New Guinea, with land in Australia.
333 4.3 Carboniferous
334 Palaeogeographic reconstructions of the Carboniferous are based on published
335 descriptions of formations of this age and a review of 14 wells (Fig. 6C). No new
336 analyses of outcrop samples were conducted by this study. Visser and Hermes
337 (1962) interpret paralic sediments across much of western New Guinea during the
338 Permo-Carboniferous (Fig. 6C) based on data from two wells, and six outcrop
339 samples. However, we interpret that the influence of marginal marine environments
340 occurred more towards the Permian. Based on the presence of conglomerates, red
341 beds and coal seams observed within the Carboniferous age Aimau, Ainim and
342 Aiduna Formations of the Bird’s Head and Neck observed within many of the 14
343 study wells, a widespread terrestrial depositional setting is interpreted for the
344 Carboniferous (Fig. 6C; Pieters et al., 1983; Fraser et al., 1993; Norvick et al., 2003).
345 This is in contrast to the interpretation of Golonka et al. (2006) where a deep water
346 slope setting is inferred along the norther margin of New Guinea.
347 Although the Aifat Mudstone is reported as marine (Pieters et al., 1983), the
348 deposition of this unit may have occurred during the early Carboniferous as the
14 349 previous period of Silurian high relative sea-level was waning. Consequently, a
350 widespread terrestrial palaeodepositional setting is interpreted across the region.
351 This is further supported by the presence of plant-bearing terrestrial sediments
352 reported from the Central Ranges (REF).
353
354 4.4 Permian
355 The Permian palaeogeography interpreted by this study is based entirely on
356 published lithological descriptions and a review of 50 wells (Fig. 6D). Of these wells,
357 13 are interpreted to contain shallow water sediments based on occurrences of delta
358 front material and shallow water limestones. Ten wells are interpreted to contain
359 terrestrial deposits comprising combinations of red beds, coals, plants and
360 freshwater palynomorphs. Our interpretation broadly agrees with Visser and Hermes’
361 (1962) interpretation of the distribution of marginal marine sediments extending
362 through the central Bird’s Head, Neck and Body (Fig. 6D). We extend the landmass
363 of Audley-Charles (1965) farther north, based on terrestrially influenced deposits
364 recorded from wells in this region.
365
366 Permian deposits of western New Guinea are distributed within a narrow terrestrial
367 zone, extending across the central Bird’s Head in the north, south into the Bird’s
368 Neck and Body (Fig. 6D). This terrestrial zone contains the land plants Glossopteris
369 and Gangamopteris plants, reported to stretch from the Irian Jaya to Papua New
370 Guinea (Fontaine, 2001). The Permian landmass of New Guinea was surrounded by
371 shallow water units, interpreted to have been deposited in water depths no greater
372 than 20m (Fig. 6D), based on the presence of shallow water limestones that contain
15 373 fusuline-algal assemblages similar to that of Ratburi Limestone in peninsular
374 Thailand (Dawson, 1993; Fontaine, 2001)
375 The northern boundary of the terrestrial zone is drawn from the extent of outcrops of
376 the Aimau, Ainim and Aiduna Formations across the Bird’s Head and Neck. The
377 southern extent of the terrestrial zone is delineated by well data. No deep-water Aifat
378 mudstone is mapped with the rest of the Aifam Group in Figure 6D as it is interpreted
379 to be older than Permian.
380
381 4.5 Triassic
382 Reconstructions of palaeodepositional environments of Triassic rocks within western
383 New Guinea are based on the distribution of the Tipuma Formation within 11 wells
384 (Fig. 6E). Evidence from outcrop and well data push the Australian-New Guinea
385 landmass and paralic sediments of Audley-Charles (1966) farther north so that much
386 of western New Guinea is emergent during the Triassic, contrasting to the
387 interpretation that northern New Guinea was within a deep waer setting at this time
388 (Audley-Charles, 1966). Our interpretations refine the palaeogeographic maps of
389 Visser and Hermes (1962) and Norvick et al. (2003) who suggest the presence of a
390 landmass extending from the central Bird’s Head, Neck and southern margin of the
391 Bird’s Body (Fig. 6E).
392
393 The age of the Tipuma Formation is reported as no older than Late Triassic
394 (Gunawan et al., 2012) based on detrital zircon ages and is described to have been
395 deposited within an arid continental setting comprising unfossiliferous red-bed
396 sequences (Visser and Hermes, 1962; Pieters et al., 1983) and fluvial deposits
16 397 (Gunawan et al., 2012; 2014). This is supported by the presence of oxidised
398 sediments and continentally derived palynomorphs reported within many of the wells
399 interpreted to contain terrestrial deposits (Fig. 6E) indicating that continental deposits
400 are widespread across much of western New Guinea and Seram during the Triassic
401 (Fig. 6E). Other wells contain paralic and/or supralittoral sediments interpreted here
402 to represent shallow water depths, deposited in less than 20m water depth, together
403 with Norian age reefal deposits reported from the island of Misool (Fig. 6E; Van
404 Bemmelen, 1949; Visser and Hermes, 1962; Audley-Charles, 1966). A restricted
405 marine environment is interpreted by Visser and Hermes (1962) to the far east of the
406 study area, here we interpret the presence of a reef north of the data points here
407 which provides the barrier by which the back-reef environment is restricted (Fig. 6E).
408
409 4.6 Early Jurassic
410 Early Jurassic sediments are reported from seven wells located in the on- and
411 offshore Bird’s Head and Body (Fig. 6F). These wells intersected terrestrial
412 sandstones of the Tipuma Formation, which continued to be deposited until the Early
413 Jurassic (Visser and Hermes, 1962; Pieters et al., 1983; Gunawan et al., 2012).
414 Consequently, a narrow zone of terrestrial deposits is interpreted to extend from the
415 Bird’s Head, into the Neck and Body (Fig. 6F), and possibly farther into Australia as
416 well as farther east along the Sula Spur. A barrier reef is interpreted to cause
417 restriction in the marine environment to the east of the study area as a continuation
418 of Visser and Hermes (1962) interpretation of the Late Triassic. By the Early Jurassic
419 wholly open marine strata are reported from the island of Misool (Visser and
420 Hermes, 1962) and deep water clays and marls are reported along the northern
421 margin of a landmass extending from the Bird’s Head and Neck, and centre of the
17 422 Body (Audley-Charles, 1966; Norvick et al., 2003). Therefore, water depths between
423 50m and 100m are interpreted to surround the central New Guinea landmass (Fig.
424 6F).
425 4.7 Middle Jurassic
426 Across western New Guinea, a period of Late Triassic to Early Jurassic terrestrial
427 deposition, lasting at least 28 Ma, was succeeded by deeper water sedimentation
428 during a transgressive event in the Middle Jurassic (Audley-Charles, 1966; Pieters et
429 al., 1990; Lunt and Djaafar, 1991; Gunawan et al., 2012; Fig. 6G). This is supported
430 by review of 37 wells containing Middle Jurassic strata and material from eight
431 outcrop locations.
432
433 Our reconstructions support Norvick et al.’s (2003) Middle Jurassic interpretation of
434 two separate small landmasses around Bird’s Head and Neck, respectively,
435 separated by shelfal clastic deposits between. Deep water settings are interpreted
436 along the northern New Guinea margin, also supporting Norvick et al.’s (2003)
437 interpretation of neritic clays found along this coast.
438
439 It is interpreted that by the Middle Jurassic, relative sea-level had increased so that
440 much of the Sula Spur was submerged, reducing the once continuous peninsula to
441 an archipelago of isolated landmasses (Fig. 6G). Two such landmasses were
442 separated by a narrow seaway with water depths between 50m and 100m (Fig. 6G).
443 Terrestrial deposits are interpreted within six wells in the central Bird’s Head and
444 southern Bird’s Neck based on the presence of continentally derived palynomorphs.
445 A deltaic system is interpreted to the west of the northern landmass (Fig. 6G) due to
446 the presence of fluvio-deltaic sediments reported within the CS-1X well and delta
18 447 plain coals and organic claystones of the Inanwantan sequence (Fraser et al., 1993).
448 These landmasses are flanked by shallow seas of water depths no greater than
449 20m, described from 18 wells. Water depths in excess of 50m are delineated by
450 outcrops of the Kopai Formation (Fig. 6G).
451
452 The Kopai Formation is described to comprise deep-water black shales and
453 limestones (Pieters et al., 1983). Close to the village of Wendesi, Kopai Formation
454 black shales contain a common ‘Macrocephalites’ ammonite assemblage. This
455 assemblage includes typical North Gondwanan species including Macrocephalites
456 keeuwensis, Sphaeroceras boehmi and Holcophylloceras indicum (Fig. 7). This
457 ‘Macrocephalites’ ammonite assemblage is assigned a Bathonian-Callovian age
458 (Westermann & Callomon, 1988; Westermann, 1992; Westermann, 2000; van
459 Gorsel, 2012) and were deposited within a distal, deep, open marine setting (van
460 Gorsel, 2012). Belemnites are also known from Papua New Guinea, Irian Jaya, Sula
461 Islands and Misool further indicating widespread open marine deposition during the
462 Middle Jurassic (Challinor, 1990).
463 The Middle Jurassic Tamrau Formation is described to comprise ammonites,
464 bivalves, and later planktonic foraminifera (Pieters et al., 1983) indicating a relatively
465 deep marine depositional environment. However, the Tamrau block is thought to be
466 allochthonous and may have been translated to its current position along the Sorong
467 Fault Zone (Fig. 1) since the Pliocene, although the amount of displacement along
468 this fault is uncertain.
469 4.8 Late Jurassic
470 Palaeogeographic reconstructions of this time interval are based on review of 35
471 wells containing Late Jurassic material and the distribution of the Kopai, Tamrau and
19 472 Woniwogi Formations of the Bird’s Head, and Demu and Lelinta Formations of
473 Misool island. No outcrop samples were collected or examined of Late Jurassic age.
474 Continued regional transgression into the Late Jurassic saw the seaway between the
475 two landmasses of the former Sula Spur attain water depths in excess of 100m (Fig.
476 6H). The deltaic system to the west of the northern landmass is interpreted to persist
477 into the Late Jurassic due to the presence of sediments reported within the CS-1X
478 well (Fig. 6H).
479 Audley-Charles (1966) plot a landmass over much of western New Guinea, with
480 bathyal settings occurring along its northern margin. We interpret this boundary to be
481 found along the central spine of New Guinea. Our interpretations again support
482 Norvick et al.’s (2003) Late Jurassic interpretation of two separate small landmasses
483 around Bird’s Head and Neck, separated by shelfal clastic deposits. Deep water
484 settings encroach around the margins of New Guinea throughout the Jurassic due to
485 transgression.
486
487 The Woniwogi, Demu and Lelinta Formations are interpreted to be deep-water
488 marine deposits, similar to the Kopai and Tamrau (Pieters et al., 1983; Hasibuan,
489 1990), based on the presence of glauconitic and argillaceous, fine-grained, distal
490 sediments and bathyal agglutinated foraminifera such as Glomospira spp, and
491 Trochammina spp. within some wells.
492 4.9 Early Cretaceous
493 Reconstructions of the Early Cretaceous are based on review of 23 wells, no outcrop
494 samples were collected from this time interval. In addition to the deep-water Kopai,
495 Tamrau, Woniwogi, Demu and Lelinta Formations, the widespread Early Cretaceous
20 496 Piniya Mudstone is also interpreted to be a deep marine deposit that comprises
497 thinly bedded glauconitic black mudstones and muddy siltstones (Pieters et al.,
498 1983). Due to the distribution of the Piniya Mudstone across the central Bird’s Head,
499 it is interpreted that the northern remnant landmass of the Sula Spur was submerged
500 at this time beneath water depths in excess of 100m (Fig. 6I). Our reconstructions
501 support those of Audley-Charles (1966) who interpret bathyal water depths depths
502 west of the Bird’s Head and in the northern half of the Bird’s Body, with neritic facies
503 to south and west of this boundary. This differs from Norvick et al. (2003) who place
504 an isolated landmass within the central Bird’s Head at this time.
505 Widespread deep water sedimentation is supported by the presence ammonites and
506 belemnites within the Kembelangan-1 well (Visser and Hermes, 1962) and carinate
507 Globotruncanid planktonic foraminifera, such as Praeglobotruncana spp.,
508 Paraglobotruncana spp. and Rotalipora spp., in the Kembelangan-1 and Noordwest-
509 1 wells. A bathymetric gradient shallows towards the south-west where water depths
510 between 50m and 100m are interpreted (Fig. 6I). This is based on the presence of
511 shelfal agglutinated and calcareous benthic foraminifera, such as Lenticulina spp.,
512 and sediments dominated by globular planktonic foraminifera including Hedbergella
513 spp., Heterohelix spp. and Ticinella spp., and lack of carinate foraminifera, within
514 wells along the southern New Guinea margin. A small area to the south of the Bird’s
515 Body remained subaerially exposed based on shallow water sandstones
516 encountered in the Cross Catalina-1 well.
517 Although the Woniwogi Formation is assigned a Late Jurassic to Early Cretaceous
518 age (Pieters et al., 1983), the planktonic foraminifera listed above (recorded from the
519 Woniwogi Formation in the Kembelangan-1 and Noordwest-1 wells) indicate a
520 restricted late Early Cretaceous, Aptian-Albian, age.
21 521 4.10 Late Cretaceous
522 Relative sea-level rise reached its peak during the Late Cretaceous where water
523 depths in excess of 100m are interpreted across much of western New Guinea (Fig.
524 6J). This is evident from data reviewed from 65 wells and six outcrop samples,
525 together with the distribution of Late Cretaceous deep-water sediments of the
526 Tamrau and Jass Formations, Piniya Mudstone, Amiri Sandstone of New Guinea
527 and pelitic rocks of the Korido Metamorphics of the island of Supiori (Fig. 6J). This
528 supports the interpretations of Visser and Hermes (1962) and Audley Charles (1966)
529 who interpret widespread open marine and bathyal facies across the entire western
530 New Guinea during the Late Cretaceous. The cause of a change in shallowing
531 direction from the Early to Late Cretaceous is uncertain, although this may be a
532 tectonic effect during a period of activity at this time.
533
534 Although our reconstructions agree with Norvick et al. (2003) that western New
535 Guinea was submerged beneath deep water during the Late Cretaceous, Norvick et
536 al. (2003) and Brash (1991) put the deposition of the Ekmai shallow water
537 sandstones within the Bird’s Neck. It is our interpretation that these have been
538 displaced to their current position through thrust faulting. The Late Cretaceous
539 shallow-water Ekmai sandstones, reported as late Campanian in age (Norvick et al.,
540 2003), are interpreted to have been deposited farther to the north-east and
541 translated to the Bird’s Neck through shortening of approximately 200km to the
542 southwest in the Lengguru Fold and Thrust Belt. This shortening accounts for the
543 presence of the shallower water larger benthic foraminifera Lepidorbitoides and
544 Pseudorbitoides in Late Cretaceous strata in the Bird’s Neck region (Visser and
545 Hermes, 1962). The ‘in situ’ facies in the Bird’s Neck are interpreted to be
22 546 represented by the deep marine Piniya Mudstone, following the trend for increasing
547 sea-level initiating in the Early Jurassic.
548 Many of the 65 wells contain diagnostic deep-water taxa, dominated by carinate
549 globotruncanid planktonic foraminifera including, but not exclusively, Abathomphalus
550 mayaroensis, Dicarinella spp., Gansserina gansseri, Globotruncana aegyptiaca,
551 Globotruncana arca, Globotruncana linneiana, Globotruncana ventricosa,
552 Globotruncanita spp., Globotruncanita stuartiformis, Helvetoglobotruncana helvetica,
553 Marginotruncana spp., Rosita spp., Rosita fornicata, Rotalipora spp.,
554 Rugoglobotruncana spp., Whiteinella spp., Whiteinella archeocretacea, and globular
555 planktonic foraminifera including Heterohelix spp., Pseudoguembelina spp. and
556 Racemiguembelina fructicosa. Where these carinate planktonic foraminifera occur in
557 abundance, this may indicate water depths in excess of 300m and an upper bathyal
558 depositional setting.
559 Campanian to Maastrichtian age sediments were collected from the Imskin
560 Limestone to the south-east of the Bird’s Head (Fig. 6J). Six samples contain deep-
561 water taxa, indicative of outer neritic to lower bathyal water depths in excess of
562 100m, including Abathomphalus mayaroensis, Contusotruncana fornicata, C.
563 plummerae, Gansserina gansseri, Globotruncana arca, Globotruncana bulloides,
564 Globotruncana linneiana, Globotruncanita conica, Globotruncanita. stuarti,
565 Rugotruncana subcircumnodifer and Heterohelix globulus (Fig. 8).
566
567 4.11 Paleocene
568 Following the Late Cretaceous relative sea-level high, water levels receded during
569 the Paleocene leaving shallower water areas around the southern Bird’s Head, Neck
570 and Body (Fig. 6K). This is based on review of 53 wells and examination of five
23 571 outcrop samples collected from the Imskin Limestone. The distribution of shallow
572 water areas up to 20m water depth is delineated by the distribution of the Waripi
573 Formation in outcrop, and encountered in wells particularly in the southern Bird’s
574 Body (Fig. 6K). This is based on the observation of the Waripi Formation to comprise
575 a shallow-water limestone containing abundant oolites, miliolids and bryozoa (Visser
576 and Hermes, 1962; Brash et al., 1991). Farther north, particularly within the Bintuni
577 Basin and offshore to the west, deeper waters in excess of 100m are encountered in
578 many wells recording Daram Formation turbiditic material and carbonate mudstones
579 comprising carinate and globular foraminifera including Morozovella spp., M. acuta,
580 M. aequa, M. angulata, M. edgari, M. inconstans, M. pseudobulloides, M.
581 velascoensis, Acarinina spp., Eugubina spp., Globanomalina spp. and Subbotina
582 spp. We interpret that the Daram turbidites in central Bird’s Head directed to the west
583 (Fig. 6K). An exception to this trend are Daram sandstones reported from islands
584 southeast of Misool which contain the larger benthic foraminifera Lockhartia and
585 Discocyclina indicating water depths between 20m and 50m during Paleocene to
586 Early Eocene (Belford, 1991).
587
588 Our reconstructions support interpretations of Norvick et al. (2003) and Golonka et
589 al. (2009) where shallow water carbonates occur along southern edge of New
590 Guinea margin and deep water settings along the northern margin. However, the
591 position of Norvick et al.’s (2003) Bird’s Head landmass is hereby reinterpreted as
592 isolated shallow water regions where the Waripi Formation in the Salawati basin
593 area consists of oolitic and bioclastic shoal limestones.
594
24 595 Five samples collected from the Imskin Limestone near the island of Rumberpon
596 were dated to be Paleocene age. All samples are interpreted to have been deposited
597 in an outer neritic to lower bathyal setting where water depths exceed 100m (Fig.
598 6K). These samples contain a planktonic foraminiferal assemblage comprising
599 globular and carinate morphologies including Acarinina coalingensis, A. primitiva,
600 Globanomalina imitata, G. ovalis, Morozovella aequa, M. angulata, M.
601 conicotruncata, Subbotina spp. and Turbeogloborotalia compressa.
602
603 4.12 Early Eocene
604 Relative sea-level fall continued into the Early Eocene and more shallow water areas
605 developed within the central Bird’s Head (Fig. 6L). This is supported from review of
606 51 wells, examination of nine outcrop samples and distribution of the Faumai
607 Limestone (Fig. 6L). There are no palaeogeographic maps of this time interval
608 produced by Visser and Hermes (1962) or Norvick et al. (2003); however our
609 reconstructions broadly support the Early Eocene interpretation of Brash et al. (1991)
610 and Golonka et al. (2009) of pelagic carbonates in the Bird’s Neck at this time. This
611 is supported by presence of carinate planktonic foraminifera observed in outcrop
612 samples.
613 The Faumai Limestone is described to contain shallow water carbonate bank and
614 shoal deposits and reefal facies (Pieters et al., 1983). This is supported by well data
615 where shallow water areas up to 20m in depth are interpreted north of the Bintuni
616 Basin in southern Bird’s Neck and Body based on the presence of alveolinids
617 including Lacazinella spp. and Fasciolites spp. Moderate water depths between 20m
618 and 50m are interpreted from the Faumai Limestone of several wells and outcrop
619 samples that contain alveolinids as well as abundant large, flat, rotaliine foraminifera
25 620 such as Assilina spp., Cycloclypeus spp., Discocyclina spp. and Operculina spp.
621 Pieters et al. (1983) date the Faumai Limestone as Middle Eocene to Oligocene in
622 age, however based on the presence of alveolinids including Alveolina globosa, A.
623 laxa, A. moussoulensis and A. subpyrenaica, and larger benthics including
624 Asterocyclina spp., Discocyclina ranikotensis, Cuvillierina spp. and Daviesina spp.
625 (Fig. 9). We interpret the Faumai Limestone to be at least as old as Early Eocene,
626 Ypresian, correlating to planktonic foraminiferal zone E1 and Indo-Pacific letter stage
627 ‘Ta2’ (Fig. 2).
628
629 Deeper water areas are interpreted to persist in the wells of the Bintuni Basin, from
630 outcrop samples collected close to the island of Rumberpon and from limestone
631 clasts in a Pleistocene conglomerate collected on the east coast of the Wandaman
632 Peninsula (Fig. 6L). The Bintuni wells contain mixtures of Early Eocene globular and
633 carinate planktonic foraminifera including Morozovella spp., M. aragonensis, M.
634 formosa, M. quetra, M. subbotinae, Acarinina spp., Acarinina nitida and Subbotina
635 spp. Rocks collected from the Imskin Limestone and Early Eocene age clasts within
636 a Pleistocene age conglomerate from the Wandaman Peninsula also suggest water
637 depths greater than 100m during the Early Eocene (Fig. 6L). Samples collected from
638 these localities contain the planktonic foraminifera Acarinina spp., Acarinina
639 bulbrooki, A. decepta, Globigerina lozanoi, Globigerinatheka spp., Morozovella
640 formosa, M. lensiformis, M. subbotinae and Subbotina spp (Fig. 9).
641
642 4.13 Middle - Late Eocene
643 The lowest Paleogene relative sea-level occurred across much of western New
644 Guinea during the Middle to Late Eocene. Shallow water areas were prevalent
26 645 across the central Bird’s Head and Seram, and extended throughout the southern
646 Bird’s Neck and Body (Fig. 6M). This is supported from review of 61 wells,
647 examination of 13 outcrop samples and distribution of units of the NGLG observed to
648 contain Middle to Late Eocene aged microfaunal assemblages (Fig. 6M). Our
649 reconstructions broadly support with Visser and Hermes (1962), Norvick et al. (2003)
650 and Golonka et al. (2009) on widespread shallow water carbonate deposition across
651 the majority of western New Guinea during the Middle to Late Eocene. In particular,
652 our reconstructions agree with Visser and Hermes’ (1962) interpretation of the shape
653 and bathymetry of an east-west oriented swathe of shallow water across the centre
654 of western New Guinea, where limestones dominated by Alveolina and Lacazinella
655 occur, and deep water around the Bird’s Neck. Our reconstructions refine Visser and
656 Hermes’ (1962) palaeogeographic interpretation of open marine facies close to the
657 Fakfak region of the Bird’s Head and Wandamen Peninsula (Fig. 6M).
658
659 Well data from the offshore Salawati and Bintuni basin areas, Arafura Sea, and
660 onshore wells indicate the presence of shallow waters no greater than 20m depth
661 punctuated by isolated reefal build-ups across most of the central Bird’s Head (Fig.
662 6M). This is based primarily on the presence of shallow water and reef-loving taxa
663 such as Alveolina spp., Fasciolites spp., Lacazinella wichmanni, Nummulites spp.,
664 Nummulites djodjarkartae, Pararotalia spp. and corals observed in wells ASA-1X,
665 Aum-1, Boka-1X, Rawarra-1, Sago-1, Sebyar-1 and TBE-1X in particular.
666 Bathymetric gradients away from the shallow water platforms drop to depths
667 approaching 50m (Fig. 6M) where large flat rotaliines including Assilina spp.,
668 Discocyclina spp., Heterostegina spp., Operculina spp. and assemblages of small
669 calcareous benthic foraminifera typical of shelf settings are found in wells East
27 670 Misool-1, Soeaboor-1, Steenkool-1 and Tarof-2. Deep water facies are interpreted in
671 the Onin wells based on the presence of Acarinina spp., Globigerinatheka spp. and
672 Morozovella spp.
673
674 Interpretations from well data are supported by outcrop evidence along the western
675 coastline of Cenderawasih Bay. Close to the village of Ransiki, shallow water facies
676 include grainstones containing large Alveolina elliptica and Nummulites gizehensis
677 within samples of the Faumai Limestone (Fig. 10). Farther to the south-east of
678 Ransiki, samples contain large flat rotaliines including Assilina exponens,
679 Asterocyclina sp. and Discocyclina sella indicative of moderate water depths. Water
680 depths between 50m and 100m are interpreted close to the island of Rumberpon
681 (Fig. 6M), where rocks of the Imskin Limestone contain the planktonic foraminifera
682 Acarinina intermedia, Globigerina tripartita, Porticulasphaera mexicana and
683 Subbotina spp. Rocks of the Imskin Limestone and Wandaman Peninsula indicate
684 outer neritic water depths in excess of 100m surrounding the Wandaman peninsula,
685 although the Wandaman samples were collected from a Pleistocene conglomerate
686 and are likely transported. Samples here contain a mixture of globular planktonic
687 foraminifera including Acarinina bullbrooki, A. decepta, A. pentacamerata, A.
688 primitiva, A. pseudotopilensis, Globigerinatheka sp., Subbotina eocaenica and
689 carinate forms including Morozovella aragonensis and M. crassata (Fig. 10).
690
691 The oldest foraminifera observed on the islands of Biak and Supiori are Pellatispira
692 sp., an exclusively Late Eocene, Priabonian, aged genus indicative of Indo-Pacific
693 ‘letter stage’ Tb (Adams, 1970; Figs. 2 & 10). These larger benthic foraminifera are
694 found reworked within clasts of Auwewa Formation material within the Batu Ujang
28 695 Conglomerate outcropping around Wafordori Bay on the north coast of Supiori.
696 Although reworked, Pellatispira sp. signify moderate water depths up to several 10’s
697 of metres within the vicinity of Supiori. This taxon is also observed within the
698 Auwewa Formation encountered in wells Apauwar-1, Muwar-1, and Niengo-1 in the
699 Mamberamo region.
700
701 4.14 Oligocene
702 Relative sea-level rose across western New Guinea during the Oligocene.
703 Palaeogeographic reconstructions of this time interval are based on review of 43
704 wells, examination of six outcrop samples and distribution of the Sirga Formation
705 (Fig. 6N). There are no palaeogeographic maps of this time interval produced by
706 Visser and Hermes (1962), although our reconstructions loosely support Brash et
707 al.’s (1991) and Norvick et al.’s (2003) interpretations of a terrestrial area in the
708 southern Bird’s Neck deepening towards the northeast. However, Norvick et al.
709 (2003) interpret an emergent region in the central Bird’s Head although evidence
710 from outcrop samples in this region support the Golonka et al. (2006; 2009) model of
711 shallow water settings in the region at this time (Fig. 6N).
712
713 The southern landmass is surrounded by shallow bodies of water based on the
714 presence of Austrotrillina spp. in several wells including ASA-1X, ASF-1X and ASM-
715 1X (Fig. 6N). Occasional reefal build-ups are interpreted farther north where
716 Nummulites spp are recorded from TBE-1X (Fig. 6N). Water depths up to 50m,
717 extensive around the southern Bird’s Head and Neck (Fig. 6N), are denoted by the
718 presence of larger benthic foraminifera including Cycloclypeus spp., Heterostegina
719 borneensis, Operculina spp. and Pararotalia spp. Moderate water depths are also
29 720 interpreted in the Salawati basin area primarily from reports of Heterostegina
721 borneensis in wells in this region (Visser and Hermes, 1962). Deeper water areas
722 (Fig. 6N) are interpreted where Oligocene aged rocks, including those of the Sirga
723 Formation, are dominated by intermediate water depth taxa such as Catapsydrax
724 spp., Globigerina ampliapertura, Globoturborotalita ouachitaensis, Paragloborotalia
725 opima recorded from Klalin-1, and Onin South-1X.
726
727 Six samples of Early and Late Oligocene age were collected from the west coast of
728 Cenderawasih Bay (Fig. 6N). Shallow water reef front facies, representing water
729 depths no greater than 10m, are found near the island of Rumberpon where samples
730 contain specimens of Neorotalia sp. and one of the last species of Nummulites, the
731 reticulate N. fichteli (BouDagher-Fadel, 2008).
732
733 Late Oligocene rocks are also observed in sedimentary lenses of the Arfak Volcanics
734 of the eastern Bird’s Head and Auwewa Formation on Supiori (Fig. 6N). These
735 samples consist of planktonic foraminiferal packstones and wackestones indicating
736 outer slope depths between 50m and 100m. Planktonic foraminifera of
737 ‘intermediate-water’ depths consist of globular morphologies including Globigerina
738 gortanii, Globigerina praebulloides, Globigerinoides primordius and Globoquadrina
739 binaiensis. However, these are found east of the Ransiki Fault (Fig. 1) and may
740 indicate deeper water depths away from the current setting and juxtaposed against
741 more shallow water rocks through movement along this fault.
742
30 743 4.15 Early Miocene
744 The Early Miocene saw the presence of widespread shallow water carbonate
745 platforms across western New Guinea and Cenderawasih Bay, with maximum water
746 depths no greater than 50m (Fig. 6O). This is supported from review of 95 wells and
747 examination of 37 outcrop samples. Early Miocene aged units of the NGLG including
748 the Kais, Koor and Maruni Limestones of New Guinea, the Wurui Limestone of
749 Yapen, and Wainukendi and Wafordori Formations of Biak and Supiori are described
750 to comprise predominantly shallow water to reefal carbonates (Visser and Hermes,
751 1962; Pieters et al., 1983; Brash et al., 1991). These units were mapped without
752 distinction between shallow and relatively deeper water facies; therefore the
753 distribution of these formations is used only to interpret water depths no greater than
754 50m to accommodate potential heterogeneity within the NGLG.
755
756 Our interpretations broadly support interpetations of Visser and Hermes (1962) and
757 Golonka et al. (2006; 2009) with the presence of a widespread shallow water,
758 sometimes reefal, carbonate platform dominated by larger benthic foraminiferal
759 limestones across much of western New Guinea, including carbonate build-ups and
760 patch-reefs in the Salawati basin area (Gibson-Robinson and Soedirdja, 1986).
761 However, we refine the area mapped by Visser and Hermes (1962) and Golonka et
762 al. (2006, 2009) south of New Guinea due to a greater number of data points specific
763 to New Guinea and new wells being drilled in the region since 1962.
764
765 A broad platform populated by reefal build-ups extending from the western Bird’s
766 Head to the Bird’s Body (Fig. 6O) was interpreted from 90 wells. These wells
767 intersect packstones, grainstones and reefal rudstones and floatstones that contain
31 768 shallow water taxa including Alveolinella praequoyi, Amphistegina spp., Austrotrillina
769 spp., Borelis spp., Flosculinella spp., Lepidocyclina spp., miliolids, Miogypsina spp.,
770 Miogypsinoides spp., Spiroclypeus spp. and other organisms including sponges,
771 coral, echinoids and bivalves. This platform was surrounded by a body of water no
772 greater than 50m in depth (Fig. 6O) based on the presence of the larger benthic
773 foraminifera Operculina spp., Heterostegina spp. and Cycloclypeus spp. Rare
774 deeper water sediments of this age occur Seram where they contain the globular
775 planktonic foraminifera Globigerinoides spp., Globigerina spp. and Catapsydrax spp.
776
777 In outcrop, many reefal carbonates are observed at the base of the Kais and Maruni
778 Limestones of the mainland and Wainukendi Formation of Biak and Supiori. These
779 reefs are mapped isolated patch reefs in Figure 6O, although their lateral extent is
780 unknown. Reefal carbonates and those deposited in moderate water depths were
781 observed to contain an abundant and diverse fossil assemblage, predominantly
782 comprising larger benthic foraminifera including: Eulepidina badjirraensis,
783 Lepidocyclina (Nephrolepidina) brouweri, L. (N.) isolepidinoides, L. (N.)
784 nephrolepidinoides, L. (N.) oneatensis, L. (N.) stratifera, L. (N.) sumatrensis,
785 Heterostegina borneensis, Miogypsina intermedia, M. kotoi, M. tani, Miogypsinoides
786 bantamensis, Mdes. dehaarti, Miogypsinodella primitiva, Miolepidocyclina,
787 Operculina sp. and Spiroclypeus tidoenganensis (Fig. 11).
788
789 4.16 Middle Miocene
790 A regional transgressive event is interpreted to have initiated in the Burdigalian (Gold
791 et al., in review) so that by the Middle Miocene much of western New Guinea was
792 submerged in water up to 100m depth (Fig. 6P), supporting interpretations of Brash
32 793 et al. (1991). Evidence for a rise in relative sea-level can be found in deep water
794 facies of the Napisendi Formation and Sumboi Marl of the islands of Cenderawasih
795 Bay, and in drowning successions at the top Maruni and Kais Limestone (Gold et al.,
796 in review). This is supported by evidence from 95 wells and 42 outcrop samples
797 analysed by this study.
798 Early Miocene shallow water carbonate platforms were replaced by more moderate
799 water depths in the Salawati and Bintuni basins, and areas south of the Bird’s Head
800 while backstepping to shallow water regions to the north-east of the island of Supiori
801 (Fig. 6P). A narrow moderate water depth carbonate platform developed on western
802 and southern margin of Bird’s Head and Neck (Fig. 6P). This broadly supports Brash
803 et al.’s (1991) interpretation of platform carbonate in the southern margin of the
804 LFTB and pelagic carbonates to the northeast.
805 Taxa indicative of moderate water depths, including Cycloclypeus spp., Operculina
806 spp., and Pseudorotalia spp., are prevalent in 18 wells distributed across western
807 New Guinea (Fig. 6P). Isolated carbonate platforms and occasional pinnacle reefs
808 are recorded in the main basins of the Bird’s Head which contain the shallow water
809 taxa Alveolinella quoyi, Flosculinella bontangensis, Lepidocyclina (N.) spp.,
810 Marginopora vertebralis, Miogypsina spp. as well as corals, red algae, bivalves and
811 echinoids. Deeper water areas are interpreted from the presence of planktonic
812 foraminiferal assemblages including the taxa: Orbulina universa, Globigerina druryi,
813 Globigerinoides subquadratus, Globigerinoides diminutus, Globigerinoides
814 bisphaericus, Praeorbulina glomerosa, Praeorbulina transitoria, Paragloborotalia
815 siakensis, Globorotalia fohsi.
816
33 817 Shallow water deposits collected from outcrop include soritid foraminifera such as
818 Marginopora vertebralis, and miliolids including Quinqueloculina spp. and
819 Alveolinella quoyi observed in the Koor Formation situated in the Tosem Mountains
820 in the northern ‘cap’ of the Bird’s Head and interbedded within the Napisendi
821 Formation on Biak. An isolated reef is interpreted near the island of Rumberpon at
822 this time (Fig. 6P), where samples contain reef-loving organisms such as
823 miogypsinid and lepidocyclinid larger benthic foraminifera.
824
825 Samples from the Kais and Maruni Limestones of the Bird’s Head and the Wafordori
826 Formation on Biak contain large flat rotaliine foraminifera including Katacycloclypeus
827 annulatus and Cycloclypeus carpenteri, lepidocyclinids including Lepidocyclina (N.)
828 brouweri, L. (N.) ferreroi, L. (N.) omphalus, L. (N.) verbeeki, miogypsinids including
829 Miogypsinoides indica, Miogypsina cushmani, M. intermedia, M. kotoi, M. regularia
830 (Fig. 12).
831
832 Deep water deposits occur in the upper parts of the Kais and Maruni Limestones and
833 Napisendi Formation, extending south to the central Bird’s Head and Cenderawasih
834 Bay (Fig. 6P). These samples contain abundant globular planktonic foraminifera that
835 indicate intermediate water depths between 50m and 100m. Examples include
836 Orbulina suturalis, O. universa, and many species of Globigerinoides including G.
837 quadrilobatus, G. trilobus, and rare Globorotalia spp. (Fig. 26).
838
839 4.17 Late Miocene
840 Relative sea-level continued to rise during the Late Miocene so that water depths
841 greater than 100m were widespread across much of the present day western New
34 842 Guinea (Fig. 6Q). Deep water facies rocks are represented by the Befoor and
843 Klasafet Formations of the Bird’s Head and Neck, encountered in 112 of the
844 reviewed wells and in 24 outcrop samples (Fig. 6Q). Visser and Hermes (1962) and
845 Golonka et al. (2006, 2009) interpret an increase in basinal settings filled by deep
846 water sediments across much of the Bird’s Head. Small reefal areas, much reduced
847 in size from the Early Miocene, are interpreted by Visser and Hermes (1962) in the
848 western Bird’s Head although we interpret slightly deeper water in these areas from
849 predominantly wireline log responses from Salawati and Bintuni basins. Norvick et
850 al. (2003) also interpret deep water sedimentation in the Bird’s Neck and Salawati
851 basin together with Vincelette (1973), Redmond and Koesoemadinata (1976), Collins
852 and Qureshi (1977) and Gibson-Robinson and Soedirdja (1986). Our
853 reconstructions differ, however, with Norvick et al. (2003) who interpret a widespread
854 shallow water carbonate platform through the centre of the Bird’s Head and Neck in
855 the Late Miocene based on the presence of Kais platform limestones, although we
856 interpret the Kais Limestones to be Early to Middle Miocene in age.
857
858 Evidence for the prevalence of water depths between 50m and 100m in the eastern
859 Bird’s Head and islands to the north of Cenderawasih Bay come from the abundance
860 of ‘intermediate-water’ species including Candeina nitida and Orbulina suturalis (Bé,
861 1977) found in outcrop samples. Farther south, in samples collected close to the
862 island of Rumberpon (Fig. 6Q), water depths in excess of 100m are interpreted due
863 to abundance of carinate planktonic foraminifera including Globorotalia plesiotumida,
864 Truncorotalia ronda and the thick-walled globular planktonics Sphaeroidinellopsis
865 subdehiscens and Globoquadrina dehiscens. These water depths are interpreted
866 from wells in the Salawati and Bintuni basins, and Arafura Sea, based on the
35 867 presence of thick-walled and carinate planktonic foraminifera including those
868 mentioned above and Dentoglobigerina baroemoensis, Globorotalia merotumida,
869 Neogloboquadrina acostaensis, Neogloboquadrina humerosa and
870 Sphaeroidinellopsis spp.
871
872 4.18 Early Pliocene
873 Open marine settings remained the dominant depositional environment across
874 western New Guinea during the Early Pliocene based on evidence from 101 wells
875 and 29 outcrop samples (Fig. 6R). Deep water facies are also recorded from the
876 Klasaman, Opmorai and Befoor Formations of the Bird’s Head, and Wardo, Korem
877 and Kurudu Formations of the islands of Cenderawasih Bay (Fig. 6R). Water depths
878 in excess of 50m are recorded from wells across western New Guinea that contain
879 microfossils assemblages dominated by globular and carinate planktonic
880 foraminifera including Globigerina spp., Globigerinoides spp., Globorotalia spp.,
881 Neogloboquadrina spp., Sphaeroidinella spp. and Sphaeroidinellopsis spp.
882
883 Relatively shallower water facies are recorded from wells to the south and west of
884 the Bird’s Head (Fig. 6R). This is supported by the presence of shallow water facies
885 including grainstones, coral floatstones and back-reef lagoonal wackestones that
886 contain the taxa Ammonia spp., Amphistegina lessonii, Calcarina spengleri,
887 Heterostegina spp., Marginopora spp., Neorotalia calcar, Pararotalia spp.,
888 Peneroplis spp., Pseudorotalia spp. and miliolids.
889
890 Outcrop samples collected from the Befoor and Klasaman Formations in the eastern
891 Bird’s Head were observed to contain abundant globular planktonic foraminifera
36 892 including many species of Globigerinoides spp., Neogloboquadrina spp., Pulleniatina
893 spp., Sphaeroidinella spp. and Sphaeroidinellopsis spp., as well as Orbulina
894 universa. Carinate planktonic foraminifera such as species of Globorotalia spp. are
895 interpreted to have been occasionally washed in to this environment and large flat
896 benthic foraminifera such as Operculina spp. are washed down slope. To the north-
897 east of the Bird’s Head, evidence for shallower reefal settings are observed with reef
898 front facies rocks of the Wai Limestone containing Calcarina spengleri, Amphistegina
899 spp. and abundant rodophyte red algae situated in front of back-reef facies units
900 (Fig. 6R). Shallow water facies, interpreted as back-reef lagoons, to the east of the
901 Bird’s Head (Fig. 6R) contain soritid foraminifera including Marginopora vertebralis,
902 small rotaliids including Quasirotalia guamensis as well as delicate corals and the
903 dasycladacean green alga, Halimeda.
904
905 On the islands of Biak and Supiori, a small bathymetric high is interpreted to pass
906 quickly from inner slope sediments into outer neritic settings indicating the presence
907 of steeply inclined slopes around the high (Fig. 6R). Outer neritic sediments
908 representing water depths in excess of 100m occur towards the Biak basin to the
909 south-west. These sediments contain common carinate planktonic foraminifera
910 including Globorotalia conoidea, G. margaritae, G. menardii, G. miocenica, G.
911 tumida, G. sphericomiozea, Truncorotalia crassula and thick walled globular
912 planktonic foraminifera Sphaeroidinellopsis seminulina. Carinate planktonic
913 foraminifera are indicative of water depths in excess of 100m were observed in deep
914 water facies of the Korem and Wardo Formations.
915
37 916 4.19 Late Pliocene
917 Regression initiating in western New Guinea towards the end of the Early Pliocene
918 resulted in more extensive and frequent shallow water areas interpreted across the
919 region by the Late Pliocene (Fig. 6S). This is supported by review of 98 wells and 29
920 outcrop samples. Deep water areas are interpreted based on the presence of
921 globular and carinate planktonic foraminifera including Globigerina spp.,
922 Globigerinoides spp., Globorotalia spp., Neogloboquadrina spp., Sphaeroidinella
923 spp. and Sphaeroidinellopsis spp. The distribution of relatively shallower areas are
924 interpreted based on the presence of large flat rotaliines including Cycloclypeus,
925 Heterostegina spp., Operculina spp. and typical back reef or lagoonal taxa such as
926 soritid and miliolid foraminifera, coral, echinoids and bivalves.
927
928 4.20 Pleistocene 929 Early Pliocene relative sea-level fall continued into the Pleistocene and up to the
930 present day in western New Guinea. Several areas of the Bird’s Head, Neck and
931 Body were submerged beneath waters no greater than 50m and localised areas
932 were subaerially exposed close to the Salawati and Bintuni basins (Fig. 6T) as a
933 precursor to the present day topography of the island of New Guinea. Our
934 reconstructions are based on evidence from 43 wells and five outcrop samples is
935 similar to Visser and Hermes’ (1962) interpretation of New Guinea in the
936 Pleistocene.
937
938 In the location of the present day islands of north of Cenderawasih Bay carbonate
939 platforms deposited shallow water and reefal facies rocks of the coeval Mokmer and
940 Manokwari Formations (Fig. 6T). At this time Cenderawasih Bay itself became a
38 941 distinct deep water feature filled by pelagic carbonates comprising planktonic
942 foraminiferal packstones.
943
944 Only five samples were collected of Pleistocene age (Fig. 6T). Four samples
945 representing the Mokmer Formation were located to the south-east of Biak and one
946 sample from the Manokwari Formation of the north-eastern Bird’s Head (Fig. 6T).
947 Palaeogeographic interpretations suggest a southwest directed deepening trend
948 across a broad carbonate platform no deeper than 50m in water into the much
949 deeper setting of Cenderawasih Bay (Fig. 6T). The presence of a carbonate platform
950 attaining these moderate water depths is indicated by common occurrences of the
951 larger benthic foraminifera Heterostegina spp., and globular planktonic foraminifera
952 including Pulleniatina obliquiloculata and Globigerinoides quadrilobatus. Rocks
953 interpreted to have been deposited in reefal, shallow water settings up to 10m in
954 depth comprise grainstones that contain abundant encrusting rodophyte red algae
955 resilient to the brunt of high hydrodynamic energies. Behind this, quiet waters of the
956 former back-reef are situated to the east of the island and contain delicate bryozoa
957 and branching corals of the genera Acropora and Porites. Dasycladacean green
958 algae, such as Halimeda, are also common. The disintegration of algal needles may
959 contribute towards the large amount of micrite in wackestones deposited in this
960 setting.
961 5. Discussion
962 5.1 Temporal Trends 963 Through the reconstruction of palaeodepositional environments using microfossil
964 assemblages, temporal trends of relative sea-level change can also be deduced.
965 Figure 13 displays a localised relative sea-level curve for the Bird’s Head region from
39 966 the Silurian to Pleistocene, based on the average water depth across western New
967 Guinea at a given time (Fig. 13).
968
969 The second highest global 1st-order sea-level highstand for the Paleozoic occurred
970 during the Silurian (Ross & Ross, 1988; Golonka, 2006) matching observations of
971 palaeobathymetries in western New Guinea at this time. Relative sea-level fall from
972 the Silurian to Devonian saw the replacement of deep water settings to terrestrially
973 dominated environments persisting from the Permian to Early Jurassic (Fig. 13).
974 Transgression throughout the Middle Jurassic and into the Cretaceous resulted in
975 peak Mesozoic relative sea-level by the Late Cretaceous (Fig. 13), the time of
976 maximum global sea-level during the Phanerozoic (Golonka et al., 2006), and the
977 deposition of many fine-grained siliciclastic formations. Relative sea-level fell
978 throughout the Paleogene until the Middle to Late Eocene when widespread
979 shallow water areas permitted the growth of extensive carbonate platforms
980 represented by the oldest units of the NGLG including the Faumai, Lengguru and
981 Imskin Limestones, and carbonate lenses within the Auwewa Formation.
982
983 Relative sea-level increased for a short duration during the Oligocene before the
984 onset and perpetuation of arc-continent collision between the Australian and Pacific
985 Plates in the earliest Miocene. This collision caused sub-aerial erosion of Paleogene
986 sediments in some areas forming a regional Early Miocene unconformity (Gold et al,
987 2014; Fig. 2). Collisional uplift within other areas, resulting in regional relative sea-
988 level fall (Fig. 13), permitted renewed widespread carbonate platform growth and
989 deposition of Early Miocene units of the NGLG.
990
40 991 Stable shallow-water carbonate deposition of the NGLG continued for at least 6 Myr
992 across much of western New Guinea until a second regional transgressive event
993 initiated in the Burdigalian (Gold et al., in review; Fig. 13). Relative sea-level rise
994 reached its peak in the Late Miocene, possibly correlating with the global Tor1
995 flooding event (Hardenbol, 1998; Gradstein et al., 2012; Gold et al., in review),
996 resulting in the deposition of widespread deep-water limestones and fine-grained
997 siliciclastics of the Klasafet and Klasaman Formations. Relative sea-level began to
998 fall again during the Pliocene and continued until the present day (Fig. 13), leaving
999 western New Guinea sub-aerially exposed as we know it today.
1000
1001 The regional Bird’s Head relative sea-level curve is similar to that of published global
1002 sea-level curves (Haq and Al-Qahtani, 2005; Müller et al., 2008; Snedden and Liu,
1003 2010) from the Silurian to Paleocene (Fig. 13). This implies that that the primary
1004 control on relative sea-level change throughout this time is eustatic. However, there
1005 are disparities between the curves from the Early Eocene to Oligocene (Fig. 13).
1006 This suggests that the primary control on relative sea-level change is more localised
1007 at this time and may be attributed to tectonic effects of regional subsidence and uplift
1008 and/or environmental controls influencing sedimentation rates. Following arc-
1009 continent collision in the Early Miocene the regional relative sea-level curve of the
1010 Bird’s Head returns to recording the signal of global eustatic sea-level change (Fig.
1011 13).
1012
1013 5.1 Comparisons with computer models 1014
41 1015 Our palaeogeographic reconstructions broadly support, and build upon, previously
1016 published palaeogeographic maps of New Guinea based on empirical data (e.g.
1017 Visser and Hermes, 1962; Audley-Charles, 1965; 1966; Brash et al., 1991; Golonka,
1018 2006; 2009) but differ to computer modelled global and regional palaeogeographies
1019 (e.g. Zahirovic, 2014; 2016, Heine et al., 2015; Leprieur et al., 2016). This is
1020 attributed to the replication of parameters unsuitable for tectonically complex regions
1021 such as Southeast Asia.
1022 Most computer models use global eustatic sea-level curves (Haq et al., 1987; 2014,
1023 Haq and Al-Qahtani, 2005; Haq and Shutter, 2008; Müller, 2008; Snedden and Liu,
1024 2010) as a basic parameter for their models and apply this to global basins, including
1025 those in Southeast Asia. The sea-level curves of Haq et al. (1987) and Haq and Al-
1026 Qahtani (2005), in particular, are based on observations from the Arabian platform.
1027 This region has a remained a relatively stable homoclinal carbonate ramp since the
1028 XXXX, thus preserves a good record of facies changes up and down the ramp
1029 enabling the determination of past relative, and regional, sea-level change.
1030 Heine et al (2015) concluded that calculations of land areas relative to the total area
1031 of continental crust extracted from the empirical data of Smith et al. (1994) and
1032 Golonka et al. (2006) produced palaeoshoreline maps that matched sea-level curves
1033 of Haq & Al-Qahtani (2005) and Müller (2008). The Smith et al. (1994) and Golonka
1034 et al. (2006) models have a sparse dataset in Southeast Asia, with no data points for
1035 New Guinea or most of Indonesia except Kalimantan. Therefore, subtle regional
1036 deep marine incursions and development of widespread carbonate platforms are not
1037 recorded in palaeogeographic reconstructions. Lepreiur et al. (2016) take a different
1038 approach to mapping the development of carbonate platforms in Southeast Asia by
1039 using a mechanistic model of species diversification combined with a model of
42 1040 synthetic paleobathymetry estimates to map the global spatial distribution of
1041 biodiversity hotspots since the Cretaceous. This approach models the migration of
1042 new species and biodiversity hotspots through time, moving east from the western
1043 Tethys through the Arabian peninsula and west Indian Ocean, arriving in the Indo-
1044 Pacific during the Miocene (15-5 Ma)(Leprieur et al., 2016). However, our models
1045 show that western New Guinea was a biodiversity hotspot where carbonate
1046 platforms flourished during the Middle-Late Eocene. Leprieur et al. (2016) remark
1047 that ecological diversification is controlled by the availability of tropical reef habitat
1048 through time. We argue that more tropical reef habitat was available earlier, during
1049 the Eocene in particular, than suggested by Leprieur et al. (2016) as indicated by the
1050 regional relative sea-level curve of Figure 13. Widespread carbonate platform
1051 development in New Guinea during the Eocene may be controlled by regional
1052 tectonism and/or favourable environmental conditions that permitted high rates of
1053 carbonate production.
1054
1055 Although our palaeogeographic reconstructions do record changes in the long-term
1056 eustatic sea-level signal for parts of the Phanerozoic, it is shown to diverge from this
1057 trend between the Eocene and Oligocene (Fig. 15). Zahirovic et al. (2016) and Yang
1058 et al. (2016) note that flooding in the Sundaland platform of Indonesia increases
1059 during the Eocene while the fraction of continental crust experiencing marine
1060 inundation decreases globally with long-term eustatic sea level fall (Haq and Al-
1061 Qahtani, 2005; Müller, 2008; Snedden and Liu, 2010; Heine et al., 2015). The
1062 mechanism for this divergence from global sea-level curves in southern Sundaland is
1063 interpreted to be due to the downwelling of mantle causing regional subsidence
1064 (Yang et al., 2016). This reinforces the interpretation that the use of published global
43 1065 sea-level curves is not appropriate for regions such as Southeast Asia where
1066 complex tectonism and favourable environmental conditions for carbonate
1067 production, having been situated in low latitudes since the at least the Triassic
1068 (Audley-Charles, 1966), may be greater controls on palaeogeography than eustatic
1069 factors.
1070
1071 Often computer modelled palaeobathymetries (e.g. Müller et al., 2008) are too
1072 coarse to be used as parameters in modelling subtle changes in palaeogeography at
1073 a regional scale. These models have the capability of computing global bathymetric
1074 changes in hundreds to thousands of metres water depth, however the use of
1075 palaeontological and sedimentological data, as shown by this study, can model
1076 changes in bathymetry at a scale from a few tens to hundreds of metres. Therefore,
1077 we interpret that bathymetric models are more precise in reconstructing regional
1078 paleogeography using empirical data and sea-level fluctuations in tectonically
1079 complex areas should not be related to global eustacy curves and relative sea-level
1080 curves should be established that are specific to the region (e.g. Fraser et al., 1993).
1081 6. Conclusions
1082 Empirical data from well and outcrop samples reveals a reasonably conformable
1083 sequence of sediments dated from the Silurian to present day. Two major
1084 transgressive-regressive cycles in relative sea-level are identified within the region.
1085 Peaks in relative sea-level are interpreted to have occurred in the Late Cretaceous
1086 and Late Miocene. These regional relative sea-level highs record a signal
1087 corresponding to peaks in the long-term trend of eustatic sea-level change Haq and
1088 Al-Qahtani, 2005; Müller, 2008; Snedden and Liu, 2010). Divergence from the long-
44 1089 term global eustatic sea-level trend during the Eocene to Oligocene is attributed to
1090 regional tectonism and/or environmental factors.
1091
1092 This study refines previous published palaeogeograpghic maps of western New
1093 Guinea using empirical data (Visser and Hermes, 1962; Audley-Charles, 1965; 1966;
1094 Brash et al., 1991; Golonka, 2006; 2009). The use of empirical data is shown to be
1095 more robust in determining regional changes in relative sea-level than computer
1096 models that use global eustatic sea-level curves as parameters (e.g. Zahirovic, 2014;
1097 2016, Heine et al., 2015; Leprieur et al., 2016).
1098
1099 If we consider that the latitude and position of New Guinea relative to Australia has
1100 not changed considerably since the Triassic then our palaeogeographic
1101 reconstructions south of the Australia-Pacific suture from the Triassic onwards are
1102 relatively robust. We are also confident in the robustness of the reconstructions
1103 using post-collisional stratigraphy of the region. However, displacements along major
1104 strike-slip fault systems such as the Sorong Fault Zone, interpreted to have initiated
1105 in the Early Miocene (Visser and Hermes, 1962; Ali and Hall, 1995), may distort the
1106 reconstructions.
1107
1108 Acknowledgments
1109 This work was supported by the Southeast Asia Research Group at Royal Holloway,
1110 funded by a consortium of oil companies. We thank our fieldwork counterparts from
1111 the Institut Teknologi Bandung as well as John Decker, Phil Teas, Angus Ferguson
1112 and Farid Ferdian (all previously of Niko Asia), together with the crew of the Shakti
1113 live-aboard vessel for assistance during fieldwork. Various staff members and
45 1114 postgraduate research students at Royal Holloway, University of London also
1115 helped. We particularly like to thank Robert Hall, Benjamin Jost and Max Webb for
1116 commenting on an earlier version of this manuscript.
1117
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62 1491 Figure Captions
1492 Figure 1. Structural map of western New Guinea. Faults were drawn based on
1493 features identified from ASTER digital elevation data, bathymetric multibeam and
1494 seismic data of the Biak and Cenderawasih Bay basins provided by TGS, and those
1495 encountered in the field. The offshore Manokwari Trough was drawn from GLORIA
1496 sonar imagery (after Milsom et al., 1992). Derived regional stresses are implied after
1497 Bock et al. (2003), and vector of Pacific-Caroline plate motion plotted after Cloos et
1498 al. (2005).
1499
1500 Figure 2. Stratigraphy of the north and eastern Bird’s Head. Established from field
1501 data of this study and modified from Masria et al. (1981); Pieters et al. (1989);
1502 Robinson et al. (1990); Pieters et al. (1990); Brash et al. (1991).
1503
1504 Figure 3. Geological map of units encountered during this study. Distribution of
1505 geological units based on original GRDC maps and fieldwork from this study
1506 (Modified from Masria et al., 1981; Pieters et al., 1989; Robinson et al., 1990; Pieters
1507 et al., 1990)
1508
1509 Figure 4. The bathymetric boundaries used in the palaeogeographic reconstructions
1510 are derived from environmental preferences of foraminifera observed in this study.
1511 Thick lines indicate environments in which foraminifera are abundant, thin lines
1512 indicate environments in which they also occur infrequently. Environmental
1513 preferences are based on field data and Bé (1977), Hallock and Glenn (1986), van
1514 Gorsel (1988), Brash et al., 1991; BouDagher-Fadel (2008, 2015), Beavington-
1515 Penney and Racey (2004), Lunt (2013).
63 1516
1517 Figure 5. Location of wells and reefs reinterpreted by this study. References for
1518 public domain data listed in Table 1.
1519
1520 Figure 6. Palaeogeographic reconstructions of western New Guinea from the Silurian
1521 to Pleistocene. Based on evidence from public domain well data, biostratigraphic
1522 reports, regional geology, sedimentological interpretations and new outcrop data.
1523
1524 Figure 7. Bathonian-Callovian aged ammonites collected from the Kopai Formation
1525 close to the village of Wendesi. A) Macrocephalites keeuwensis, B) Sphaeroceras
1526 boehmi and C) Holcophylloceras indicum
1527
1528 Figure 8. Age-diagnostic Late Cretaceous planktonic foraminifera, and key
1529 palaeoenvironmental indicators, observed in outcrop samples. A-D) Carinate
1530 morphologies indicative of water depths greater than 100m. E-F) Globular planktonic
1531 foraminifera. Key - Globotruncana spp.(G), Contusotruncana fornicata (C.f),
1532 Globotruncana arca (G.a), Globotruncana bulloides (G.b), Heterohelix globulus.
1533 (H.g).
1534
1535 Figure 9. Age-diagnostic Early Eocene foraminifera, and key palaeoenvironmental
1536 indicators, observed in outcrop samples. A-E) Large, flat, rotaliine foraminifera
1537 indicative of water depths between 20m and 50m from the Faumai Limestone. F)
1538 Globular planktonic foraminifera indicative of water depths between 50m and 100m,
1539 Imskin limestone. G-H) Deep-water facies containing carinate planktonic foraminifera
1540 indicative of water depths in excess of 100m, Imskin Limestone. Key - Alveolina spp.
64 1541 (A), Asterocyclina spp. (As), Alveolina subpyrenaica (A.s), Alveolina moussoulensis
1542 (A.m), Discocyclina ranikotensis (D.r), Alveolina globosa (A.g), Planostegina spp.
1543 (O), Daviesina spp. (D), Nummulites spp. (N), Acarinina spp. (Ac), Globigerinatheka
1544 spp. (Gt), Morozovella spp. (Mz).
1545
1546 Figure 10. Age-diagnostic Middle – Late Eocene foraminifera, and key
1547 palaeoenvironmental indicators, observed in outcrop samples. A-B) Shallow water
1548 facies from the Faumai Limestone. C-D) Shallow water facies observed in limestone
1549 lenses of the Auwewa Formation from Supiori. E-G) Globular planktonic foraminifera
1550 indicative of water depths between 50m and 100m, Imskin Limestone. H) Deep-
1551 water facies containing carinate planktonic foraminifera indicative of water depths
1552 greater than 100m, Imskin Limestone. Key – Nummulites gizehensis (N.g),
1553 Pellatispira spp. (Pt), Acarinina spp. (Ac), Globigerinatheka spp. (Gt), Acarinina
1554 pentacamerata (A.pe), Acarinina bullbrooki (A.b), Subbotina spp. (Sb), Acarinina
1555 primitiva (A.pr), Daviesina spp. (D), Morozovella spp. (Mz).
1556
1557 Figure 11. Age-diagnostic Early Miocene foraminifera, and key palaeoenvironmental
1558 indicators, observed in outcrop samples. A-D) Shallow water, reefal, grainstones of
1559 the Maruni Limestone. E) Shallow water packstone of the Kais Limestone. F) Large,
1560 flat, rotaliines indicate water depths between 20m and 50m in the Maruni Limestone.
1561 Key – Lepidocyclina sumatrensis (L.s), Lepidocyclina brouweri (L.b), Planorbulinella
1562 larvata (P.l), Spiroclypeus tidoenganensis (S.t), Eulepidina spp. (Eu), Miogypsina
1563 spp. (Mg), Amphistegina spp. (Am), Heterostegina spp. (Hs).
1564
65 1565 Figure 12. Age-diagnostic Middle Miocene foraminifera, and key
1566 palaeoenvironmental indicators, observed in outcrop samples. A) Large, flat,
1567 rotaliines indicating water depths between 20m and 50m from the Maruni Limestone.
1568 B) Shallow water wackestone containing taxa indicative of water depths no greater
1569 than 20m. C-D) Globular planktonic foraminifera indicating water depths between
1570 50m and 100m from near the top of the Maruni Limestone. Key – Katacycloclypeus
1571 annulatus (K.a), Borelis melo (B.m), Globigerinoides quadrilobatus (G.g), Orbulina
1572 universa (O.u).
1573
1574 Figure 13. Relative sea-level curve based on average bathymetry in western New
1575 Guinea compared to global sea-level curve of Snedden and Liu (2010). Two main
1576 transgressive-regressive cycles are interpreted with peak relative sea-level occurring
1577 during the Late Cretaceous and Late Miocene.
66