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Sequence stratigraphy of upper Eocene and Oligocene limestones, Teweh area, central Kalimantan
... The Tertiary Kutai Basin of East Kalimantan and its eastward extension into the modern marine Makassar Straits between Borneo and Sulawesi is the focus of this study (Fig. 1). Varied carbonate systems including isolated and land-attached platforms, mixed carbonate-clastic shelves, and more localized and ephemeral carbonates from the study area have a near-complete Cenozoic record (van de Weerd and Armin), Saller et al. (1993, Moss (1999), Hall (2001), Saller and Vijaya (2002), Wilson and Evans (2002), and Camp et al. (2009 Camp et al. ( ). 1992 Saller et al. 1992 Saller et al. , 1993 Wilson et al. , 2012). The sedimentology and to a lesser extent biota of these carbonates is relatively well documented (Table 1; Saller et al. 1992 Saller et al. , 1993 Saller et al. , 2010 Wilson et al. , 2012 Wilson and Evans 2002; Novak et al. 2013; Rösler et al. 2015; Santodomingo et al. 2015). ...
... Varied carbonate systems including isolated and land-attached platforms, mixed carbonate-clastic shelves, and more localized and ephemeral carbonates from the study area have a near-complete Cenozoic record (van de Weerd and Armin), Saller et al. (1993, Moss (1999), Hall (2001), Saller and Vijaya (2002), Wilson and Evans (2002), and Camp et al. (2009 Camp et al. ( ). 1992 Saller et al. 1992 Saller et al. , 1993 Wilson et al. , 2012). The sedimentology and to a lesser extent biota of these carbonates is relatively well documented (Table 1; Saller et al. 1992 Saller et al. , 1993 Saller et al. , 2010 Wilson et al. , 2012 Wilson and Evans 2002; Novak et al. 2013; Rösler et al. 2015; Santodomingo et al. 2015). The diversity of both carbonate systems and marine biota within the region allows evaluation of the interplay between the two systems and is particularly pertinent to evaluating biodiversity partitioning within biodiversity hotspots. ...
... In comparison with the Kutai Basin, the adjacent Makassar Straits have been a region of globally important oceanic throughflow between the Pacific and Indian Oceans since at least the Oligocene (the Indonesian Throughflow; Kuhnt et al. 2004; Gordon 2005). The northeasterly and southeasterly protrusions of basin margin structural highs into the Makassar Straits were sites of extensive (. 100-km-across) predominantly Oligo-Miocene carbonate platform development of the Taballar and Berai Limestones on the Mangkalihat and Adang Highs, respectively (Figs. 1 and 2; van de Weerd and Saller et al. 1992 Saller et al. , 1993 Wilson and Evans 2002). A number of other smaller-scale platforms up to tens of kilometers across developed within the basin and Makassar Straits, probably also on localized structural highs (Roberts et al. 1988; Moss and Chambers 1999; Wilson et al. , 2012 Saller and Vijaya 2002). ...
A holistic approach is adopted here to evaluate basin-wide trends in carbonate systems, their subenvironments and the potential marine biodiversity partitioning between different habitats within the Coral Triangle biodiversity hotspot in central Southeast Asia. The Central Indonesian Kutai Basin is typical of many Cenozoic Southeast Asian basins in having extensive and varied carbonate systems, and is one of the few regions in the Coral Triangle with detailed systematic multitaxon evaluation of Oligo-Miocene deposits. The Kutai Basin may therefore provide data, when compared with other modern and global datasets, to better understand marine biodiversity development within the global diversity foci. Carbonate systems in the Kutai Basin included small-scale ephemeral features, such as delta-associated patch reefs, mixed carbonate-clastic shelves, and large-scale (> 10 km) land-attached and isolated carbonate platforms affected by varied energy regimes. Twenty-five–plus subenvironments or habitats are spread across the different carbonate systems, with the large-scale platforms hosting over 12–15 different habitats. These subenvironments include clastic-influenced mesophotic coral reefs/carpets, nonclastic- and clastic-influenced sea-grass beds, downslope reworked coral rubble, and shallow low-energy inner platform areas, to name a few. Perhaps paradoxically, the systems that two decades ago were almost unstudied, the clastic-influenced coral reefs/carpets, are now the only ones in the region to have been systematically studied for their marine biota. Detailed biotic studies have therefore only investigated < 4 of the 25-plus potentially habitable carbonate subenvironments within the basin. This variability of carbonate systems and their subenvironments, but paucity of detailed biotic data is typical of many basins within equatorial Southeast Asia. It is recognized that detailed multitaxon biotic studies are in their infancy for Southeast Asia, and that there are challenges of taxonomic bias and/or preservation for many groups within the fossil record. Currently, however, we cannot evaluate marine biodiversity partitioning across the varied habitat mosaics of Southeast Asian carbonate systems with possible pathways discussed for furthering this field of research. It is likely that we are (?grossly) underestimating biodiversity on a basin-wide and probably a system-wide scale. It is hoped that studies of this type will contribute towards better understanding of equatorial marine carbonate systems, their biological inhabitants and producers, and the spatio-temporal development of global biodiversity hotspots.
... During the Late Eocene, on both the northern and southern margins of the basin, extensive carbonate platforms were developed. For example Upper Eocene argillaceous limestones with larger foraminifera occur below Oligocene carbonates in the Panain-Gunung Anga and Kerenden areas of the southern margin of the basin (Saller et al., 1992Saller et al., , 1993) as well as in the Bungalun River Area (Wilson et al., 1998). ...
... Marine Carbonates Batu Belah Limestone Member, Berai Formation, Taballar Formation, Batu Hidup Formation, Kedango Limestone) In parts of the basin, carbonate deposition was continuous from the Late Eocene to the Late Oligocene sag phase, but restricted to basement high areas such as the Bungalun River and Kerenden, and to basin margin areas (van de Weerd et al., 1987; Saller et al., 1992 Saller et al., , 1993 Moss et al., 1997). Carbonates on the northern side of the basin are less well-known (see Wilson et al., 1998) but are analogous in age and facies to the Berai Limestone of the Upper Berai Formation on the southern basin margin (van de Weerd et al., 1987; Saller et al., 1992 Saller et al., , 1993 ). ...
... Marine Carbonates Batu Belah Limestone Member, Berai Formation, Taballar Formation, Batu Hidup Formation, Kedango Limestone) In parts of the basin, carbonate deposition was continuous from the Late Eocene to the Late Oligocene sag phase, but restricted to basement high areas such as the Bungalun River and Kerenden, and to basin margin areas (van de Weerd et al., 1987; Saller et al., 1992 Saller et al., , 1993 Moss et al., 1997). Carbonates on the northern side of the basin are less well-known (see Wilson et al., 1998) but are analogous in age and facies to the Berai Limestone of the Upper Berai Formation on the southern basin margin (van de Weerd et al., 1987; Saller et al., 1992 Saller et al., , 1993 ). The location of antecedent topography, such as basement highs and crests of fault blocks, still clearly in¯uenced the development of this facies within the basin (Fig. 8). ...
The Kutai Basin occupies an area of extensive accommodation generated by Tertiary extension of an economic basement of mixed continental/oceanic affinity. The underlying crust to the basin is proposed here to be Jurassic and Cretaceous in age and is composed of ophiolitic units overlain by a younger Cretaceous turbidite fan, sourced from Indochina. A near complete Tertiary sedimentary section from Eocene to Recent is present within the Kutai Basin; much of it is exposed at the surface as a result of the Miocene and younger tectonic processes. Integration of geological and geophysical surface and subsurface data-sets has resulted in re-interpretation of the original facies distributions, relationships and arrangement of Tertiary sediments in the Kutai Basin. Although much lithostratigraphic terminology exists for the area, existing formation names can be reconciled with a simple model explaining the progressive tectonic evolution of the basin and illustrating the resulting depositional environments and their arrangements within the basin. The basin was initiated in the Middle Eocene in conjunction with rifting and likely sea floor spreading in the Makassar Straits. This produced a series of discrete fault-bounded depocentres in some parts of the basin, followed by sag phase sedimentation in response to thermal relaxation. Discrete Eocene depocentres have highly variable sedimentary fills depending upon position with respect to sediment source and palaeo water depths and geometries of the half-graben. This contrasts strongly with the more regionally uniform sedimentary styles that followed in the latter part of the Eocene and the Oligocene. Tectonic uplift documented along the southern and northern basin margins and related subsidence of the Lower Kutai Basin occurred during the Late Oligocene. This subsidence is associated with significant volumes of high-level andesitic–dacitic intrusive and associated volcanic rocks. Volcanism and uplift of the basin margins resulted in the supply of considerable volumes of material eastwards. During the Miocene, basin fill continued, with an overall regressive style of sedimentation, interrupted by periods of tectonic inversion throughout the Miocene to Pliocene.
... Larger benthic foraminifera and coralline algae dominate the platform interior carbonates (Fig. 7). On the northern margin of the main Berai Platform four Oligocene carbonate sequences, each 200– 500 m thick, have been identified from onshore seismic and outcrop data (Saller et al., 1992Saller et al., , 1993). Sequence boundaries vary from angular unconformities related to tectonic tilting to conformable boundaries associated with either renewed carbonate production or backstepping of the margin. ...
... Sequence boundaries vary from angular unconformities related to tectonic tilting to conformable boundaries associated with either renewed carbonate production or backstepping of the margin. In the second and third sequences, deposits, although aggradational, contain southward-dipping shingled clinoforms indicating progradation of shelf margin carbonates into the platform interior (Saller et al., 1992). This southerly transport direction is the same Tyrrell and Christian, 1992; Erlich et al., 1990; 1993; Moldovanyi et al., 1995 Wonosari as the predominant current direction on the modern Pater Noster Platform. ...
... This southerly transport direction is the same Tyrrell and Christian, 1992; Erlich et al., 1990; 1993; Moldovanyi et al., 1995 Wonosari as the predominant current direction on the modern Pater Noster Platform. Platform interior facies from the Oligocene shelf and the small-scale (11–16 km diameter) isolated Kerenden Platform to the north, are dominated by packstones and wackestones, with grainstones becoming more common towards the margins (Saller et al., 1992Saller et al., , 1993 Saller and Vijaya, 2002 ). During highstand periods, platform interior facies commonly accumulated in low-energy lagoonal areas and contain abundant miliolids and rotaliids (Saller et al., 1992). ...
Recent studies of low-latitude carbonates from SE Asia and Australia have revealed deposits and platform-types that do not fit easily into the perceived view of ‘warm-water’ tropical carbonates. The sediments are classified as a foramol or foralgal facies, and are dominated by non-framework building, light-dependent biota such as perforate larger benthic foraminifera, coralline algae and sometimes Halimeda. Although ancient foramol deposits are often interpreted as an indication of non-tropical conditions, foramol facies have long been known from the tropics, yet the environmental conditions in which they form are poorly known. The aims of this paper are to evaluate how these deposits are best classified, and more importantly whether there are any overriding controls that influence their common development in low-latitude areas, and if resultant platform development is affected.
... Also, at this time, deposition of the Berai Limestone of southeast Kalimantan initiated (Saller et al. 1992(Saller et al. , 1993. Reports of an Eocene age at the base of the carbonate in Saller and Vijaya (2002) are based on a single specimen of Nummulites variolarius, which, as described in Lunt (2019c), is not a marker for an Eocene age. ...
In Southeast Asia, Cenozoic carbonates commonly were initiated or terminated at times of tectonic change, and they are bound by unconformities. A review of the timing of several of the largest unconformities shows they correlate over wide areas. These unconformities divide the stratigraphic record of Sundaland into episodes, with times of rapid basinal re-adjustment separated by periods of relative stasis. These generalizations are true not only in the successions deposited during the dominantly extensional later Eocene to early Miocene, but also in the often-compressional middle Miocene and younger deposits, in which at least three phases of rapid tectonic and stratigraphic change can be correlated over multiple depocenters. A detailed review of many areas of Southeast Asia using quantitative biostratigraphic methods indicates that tectonism resulted in relative changes in sea level, with no indication that eustasy was an important driving force.
The boundaries between these sedimentary episodes vary in their effect and distribution, depending upon the tectonic cause. As a consequence, there is no uniform subdivision of the stratigraphic record across the region, which precludes a simple Sundaland-wide classification of primary sedimentary sequences. This review concentrates on both event timing and rates of change within and between basins, especially those changes that initiated or terminated carbonate deposition. In addition, some short-lived carbonate buildups that developed during transitional periods are described.
This review provides the beginnings of a new stratigraphic framework for the Cenozoic carbonates and related deposits of Southeast Asia. It requires an inductive analytical methodology, in contrast to the model-driven and deductive approaches that have been applied in recent years. This episodic stratigraphy approach includes integration of large amounts of analytical data, for which the Cenozoic tropical sediments of Southeast Asian basins are particularly well suited.
... The current best estimate for the major eustatic sea-level fall is at about 29.6 Ma (Haq et al. 2005), so this remains a candidate to have been the cause of this event. Saller et al. (1992Saller et al. ( , 1993 gave the age for the drowning of the Berai carbonate platform in Central Kalimantan, 500 km to the south (Figure 1), as 28.0 Ma based on the strontium isotope ratio versus time curve of Miller et al. (1988). However, as noted by Wannier (2009), the lack of species-specific data on the foraminifera limits the value of their strontium age. ...
A review of the biostratigraphy of the Melinau Limestone with strontium dating
... Several authors (van de Weerd and Armin, 1992) give a Late Eocene age to the Keliam volcanics some 250 km to the North of the Tanjung field and Bauman (1972) has described Late Eocene and Oligocene deep marine shales with rare basalt flows overlying Middle Eocene non-marine to shallow marine clastics. In addition a weak Middle Oligocene unconformity is reported by van de Weerd et al. (1987) and Saller et al. (1992) point out that the major eustatic sea level fall predicted by Haq et al. (1987) is not recognised in Central Kalimantan. ...
... Therefore, the impacts of an open-pit coal mine on groundwater become a major problem related to the role of groundwater as resources. Despite many studies on geological [8] [9][10] [11] and hydrological [12][13] [14] conditions in Central Kalimantan, there are few study on the hydrogeological conditions and in particular the quantitative approach by which the influence of open-pit coal mine on groundwater can be predicted. Therefore, it is important to develop a conceptual model as a part of groundwater flow modeling in open-pit coal mine areas. ...
Coal mining industries play an important role in the regional economics of Indonesia by producing a substantial amount of resources. In particular, many mining companies are widespread in Kalimantan Island. However, mining with an open-pit system often deteriorates the surrounding environment. The impact of the mining on the groundwater should be evaluated. Since groundwater is influenced by both natural processes and other artificial processes, it is required to construct the conceptual model of groundwater flow around open-pit coal mine areas for assessing the groundwater resources and predicting the impacts. In this study, a conceptual model was constructed based on natural groundwater flow system by considering hydrological, geological, and hydrogeological conditions in the research area. The data on meteorology, topography, boreholes, slug tests, water table, and river properties were collected and evaluated. The results showed that the research area consisted of two aquifer layers, separated by three aquitard layers. Hydraulic conductivities of both aquifer layers were 1.5 x 10-5 m/sec while the conductivities of the aquitards 1 to 3 were 1.0 × 10-6 m/sec, 3.7×10-6 m/sec, and 5.0×10-6 m/sec, respectively. Additionally, the recharge of the modeled area was 688 mm/year, with the groundwater flowing slightly from the southern to the northern part of the research area. This indicates that a tremendous amount of groundwater resources exists around open-pit areas. Consequently, the groundwater protection and management should be concerned.
... The northern platforms are younger than those on the southern margin (Qiu and Wang, 2001;Wei et al., 2005). Various examples of Indo-Pacific carbonate platforms have been described, and associated facies models presented, e.g., the Miocene Luconia platform (Epting, 1980), the Middle Oligocene Berai Limestone (Saller et al., 1992) and the Miocene Natuna buildup (Rudolph and Lehmann, 1989). However, the stratigraphic architectures of these systems and the geological factors controlling their development are often unclear. ...
Newly acquired seismic data allow improved understanding of the architecture and evolution of isolated carbonate platforms on the continental slope of the northern South China Sea. The Xisha carbonate platforms initiated on a basement high, the Xisha Uplift, in the early Miocene and have remained active to the present. Their distribution is limited to pre-existing localized, fault-bounded blocks within the Xisha Uplift so individual platforms were small in size at the beginning of the Miocene. However, during the middle Miocene, the platform carbonate factories flourished across an extensive area with 55,900 km2. The platforms began to backstep in response to a relative sea-level rise in the late Miocene. Platform-edge reefs, patch reefs, pinnacle reefs, atoll reefs and horseshoe reefs, all developed on various platforms. The distribution of platform carbonates shrank significantly during Pliocene-Quaternary time to isolated carbonate platforms, represented today by Xuande Atoll and Yongle Atoll. Tectonics and eustasy were the two main controls on platform development. Tectonics controlled both the initial topography for reef growth and the distribution of platforms, including those that survived the drowning event associated with the late Miocene rapid relative sea-level rise. Eustasy controlled high-frequency carbonate sequence development.
... Haq et al., 1987;Miller et al., 2005), and in a region such as Southeast Asia, which has a complicated history of deformation, uplift and subsidence, correlating sedimentary successions with global sea-level curves is problematical (e.g. . For example, in Central Kalimantan during a major mid-Oligocene (30-29.5 Ma) sea-level fall reported by Haq et al. (1987), platform carbonates were drowned during tectonically-driven subsidence (Saller et al., 1992). Oxygen isotope (d 18 O) curves (e.g. ...
The Barito Basin in southeast Kalimantan contains a thick, and well exposed Cenozoic sedimentary succession. The Tanjung Formation represents the oldest part of the succession, and was deposited in a largely terrestrial setting followed by a transgression to shallow marine deposition. The formation is well exposed along the eastern margin of the basin, and this has provided a rare opportunity to study and date the earliest stages of basin development. There has been considerable debate over the age of the formation, and most previous interpretations suggest it to be a deltaic succession. The provenance of the Tanjung Formation has never been studied. Palynomorphs and foraminifera of this study have established that the Tanjung Formation was deposited from late Middle Eocene, until the late Early Oligocene. Detailed facies and palaeocurrent analysis suggest the majority of the formation was deposited in a tidally-influenced coastal plain and estuarine setting, and sediment was transported by rivers flowing towards the north. Heavy mineral assemblages and zircon geochronology have identified the Schwaner Complex in west Borneo, the Karimunjawa Arch and the southern continuation of the Meratus Complex currently submerged under the Java Sea, as the main sediment sources of the formation. (c) 2012 Elsevier Ltd. All rights reserved.
... Continued post-rift sag and subsidence of the platform are probably the reason for the apparent lack of Oligocene subaerial exposure . This is comparable with nearby large-scale platforms from around the borders of the Kutai Basin and broader Makassar Straits region, in which shallow water carbonate sedimentation continues unabated through the Oligocene, with the minor exception of exposure and/or truncation of strata on the crests of tilted footwall highs (Saller et al., 1992(Saller et al., , 1993Wilson et al., 2000). The Early Miocene is the first time there is evidence for localised emergence of the Kedango platform top, with eustatic sea level fall(s) or tectonism both possible causes. ...
The variability in low to moderate energy carbonate platform margins is poorly known from the geological record. Here, the spatial and temporal evolution of platform margin and adjacent basinal deposits is evaluated from the little known Tertiary Kedango Limestone that developed in a semi-enclosed marine embayment in SE Asia. The hypothesis here is that platform margin development will reflect regional and perhaps global influences, such as tectonics, eustasy or biotic change, rather than windward-leeward effects and storms that typically impact strongly upon open oceanic platforms.
... This study describes the development and depositional environments of carbonates in northeast Borneo and helps to constrain models for sedimentation and Tertiary basin evolution in the area. Carbonate sedimentation occurred in a variety of depositional environments, ranging from mixed carbonate±clastic shelves, localised and transient foraminiferal shoals and patch reefs, extensive carbonate platforms to slope and deeper water basinal areas ( Figs. 1 and 2 Suessli, 1976;Buchan et al., 1971;Achmad and Samuel, 1984; Van de Weerd et al., 1987;van de Weerd and Armin, 1992;Saller et al., 1992; analysis of these diverse carbonates provides analogues for other SE Asian carbonates developed in similar settings. ...
Modern and Tertiary carbonate production is, and was, extensive and diverse in the seas surrounding Borneo, and mirrors the variety of carbonate depositional systems seen in SE Asia. The availability of favourable conditions for carbonate sedimentation around Borneo was related to a combination of factors, including tectonic setting, the formation of large basinal areas, differential subsidence providing shallow marine areas, a tropical climate and a range of local factors, such as currents or limited clastic input. A detailed sedimentological and diagenetic study was undertaken of middle Eocene to Plio–Pleistocene carbonates which developed in the north Kutai Basin and the Mangkalihat Peninsula, northeast Kalimantan. Carbonate sedimentation in this area occurred in a range of depositional environments, from mixed carbonate clastic shelves, localised and transient shoals or reefs, a variety of platform top settings to deep water redeposited carbonates. An understanding of carbonate depositional environments, spatial facies relationships, and diagenesis is essential in order to develop models for these carbonates which can be used as predictive tools in the subsurface. This study also helps to evaluate tropical carbonate development in SE Asia and the evolution of sedimentary environments in Borneo during the Cenozoic.
... Various examples of carbonate development and depositional facies models have been described in the Indo-Pacific region: e.g. the Miocene Luconia buildups (Epting, 1980), the Middle Oligocene Berai Limestone (Saller et al., 1992), the Miocene Natuna buildup (Rudolph and Lehmann, 1989;Dunn et al., 1996). However, the role of tectonics on the development patterns and stratigraphic architecture of these systems is only documented in a few cases: the Eocene to Middle Miocene Tonasa carbonate platform of South Sulawesi (Wilson, 1999(Wilson, , 2000Wilson et al., 2000), and the Late Eocene to Miocene Gunungh Putih carbonate complex (Cucci and Clark, 1993). ...
The comprehensive subsurface database of the Malampaya buildup (Late Eocene to Early Miocene, offshore NW Palawan) provides a rare insight into the development of South-East Asian Cenozoic carbonate systems and their controlling factors. The newly acquired high-resolution three-dimensional seismic survey, combined with facies and well-log analysis, allowed a better understanding of the internal architecture of a carbonate platform whose development was largely controlled by tectonic deformation. The Malampaya carbonate system was initiated in the Late Eocene, as an attached shelf influenced by significant clastic input. The Late Eocene–Early Oligocene shelf was subject to syn-depositional extensional tectonics (eastward tilting and block faulting) that favoured the development of small size buildups on structural highs. After a stage of eastward reef progradation, an aggrading carbonate shelf, frequently affected by subaerial exposure, developed from the earliest Late Oligocene to the Early Miocene. During this period, recurrent reactivation of highs along the western and northeastern buildup margins determined the asymmetric morphology and internal architecture of the carbonate system. The final demise of the carbonate buildup occurred in the late Early Miocene. It resulted from an increase in subsidence rate and/or a sharp increase in nutrient input. Additional parameters like eustacy, oceanographic conditions and the type of carbonate producers played a subordinate role in the buildup development and ultimate demise.
The availability of 3D seismic data undoubtedly plays an important role in reservoir characterization. Currently seismic technology continues to advance at a rapid pace not only in the acquisition but also in processing and interpretation domain. The advance on this is well supported by the digitalization era which urges everything to run reliably fast, effective and efficient. Thanks to continuous development of IT peripherals we now have luxury to process and handle big data through the application of machine learning. Some debates on the effectiveness and threats that this process may automating certain task and later will decrease human workforce are still going on in many forums but still like it or not this machine learning is already embraced in almost every aspect of our life including in oil & gas industry.
Carbonate reservoir on the other hand has been long known for its uniqueness compared to siliciclastic reservoir. The term heterogeneous properties are quite common for carbonate due to its complex multi-story depositional and diagenetic facies. In this paper, we bring up our case where we try to unravel carbonate heterogeneity from a massive tight gas reservoir through our machine learning application using the workflow of supervised and unsupervised neural network. In this study, we incorporate 3D PSTM seismic data and its stratigraphic interpretation coupled with the core study result, BHI (borehole image) log interpretation, and our regional understanding of the area to develop a meaningful carbonate facies model through seismic neural network exercises. As the result, we successfully derive geological consistent carbonate facies classification and distribution honoring all the supporting data above though the limitation of well penetration in the area. This result then proved to be beneficial to build integrated 3D geomodel which later can explain the issue on different gas compositions happens in the area. The result on unsupervised neural network also able to serves as a quick look for further sweetspot analysis to support full-field development.
The architecture and distribution of Late Oligocene–Early Miocene carbonate platforms and reefs are studied for the first time, using reprocessed 2D seismic data in the Liyue Basin, southern South China Sea. The reef complexes developed at higher positions of fault block platform and horst platform. Fault block platforms are the most important for reef development. In addition, most reefs developed in the Northern I Sag, and a few developed in the Middle Uplift. The growth processes of reefs on the platform were subdivided into six reef‐building units and two building stages. The first stage, including units 1–3, displayed slow backstepping and rapid keep up. The second stage was a rapid backstepping process that included the reef‐building units 4–6. Palaeogeomorphology, sea‐level fluctuations, and later volcanic activities were the main controls for reef occurrence. Palaeogeomorphology provided the initial topography for reef growth, and sea‐level fluctuations in combination with tectonic activity influenced reef development including growth and changing facies. Later volcanoes have strongly destroyed the pre‐existing carbonate platforms and reefs. By comparing with the carbonate reservoirs properties of adjacent regions, it is considered there is great potential for oil and gas exploration in the Liyue Basin.
Keywords: Cenozoic Syntectonic carbonate platform Marine meteoric and burial diagenesis Sulawesi in equatorial SE Asia Fracturing The influence of coeval tectonics on carbonate platform development is widely documented, yet the diagenesis of such syntectonic platforms is barely evaluated. An outcrop, petrographic and geochemical study details here for the first time the diagenesis of the Tonasa Limestone Formation developed in an extensional regime in central Indonesia. This equatorial carbonate system was affected by block faulting, tilt-block rotation, differential uplift and subsidence throughout its Eocene to Early Miocene history (Wilson, 1999; Wilson et al., 2000). The Tonasa carbonate platform is dominated by alteration in shallow to deeper burial depths by fluids with predominantly marine precursor origins. Mechanical and chemical compaction features are common, as are a range of mainly burial-related granular mosaic, blocky and equant calcite cements. Earlier marine cements and meteoric influences are rare, being highly localised to block faulted highs and/or bathymetrically upstanding platform margin areas. Early marine micritisation of allochems was common on the platform top. Tectonic uplift together with a major oceanic throughflow current are thought to be key influences on localised karstification, meteoric diagen-esis and marine cementation. The distribution and orientation of faults, fractures and calcite veins together with evidence for their relative timing are the strongest manifestation of tectonism coeval with diagenesis. There is concordance in the orientation and timing of structures affecting the Tonasa Platform with those basin-wide, with the potential for reactivation of pre-existing basement fabrics. Tectonic subsidence, including fault-associated differential subsidence, controlled the degree of burial diagenesis impacting different areas of the platform. A predominance of burial diagenetic features and dearth of earlier marine or meteoric cementation is seen in other Tertiary equatorial platforms and is partly attributed to: (1) predominance of non-framework building larger benthic foraminifera and/or algae that are prone to remobilisation, have low production rates and limited potential to build to sea level, and (2) high runoff due to the equatorial humid climate contributing to lowered marine salinities in SE Asia. Underlying tectonic reasons for the preponderance of a " regional " diagenetic signature over a " syntectonic " one, fracturing excepted, are: (1) development on the flanks of a backarc basin not on typical continental crust, (2) key platform influencing structures are oblique to the main extensional direction in the basin, and (3) development in an overall subsiding tectonic regime, postdating basin initiation. The aim here is that this study will contribute to understanding diagenetic alteration of syntectonic carbonate platforms, and those from equatorial regions.
The stratigraphic framework of the Neogene fossil vertebrate bearing formations of the Indonesianislands Sulawesi and Flores is established and the sediments are dated by means of marinemicropalaeontological and/or palaeomagnetic methods. The results allow comparison of the faunaevolution on these islands with the better known fauna succession of Java. On both Sulawesi and Flores remains of large mammals and reptiles were excavated from fossil-rich layers, documenting the composition of large vertebrate faunas fairly well. For Sulawesi this procedure allows distinction of separate fauna units which formerly had been lumped together. Both on South-Sulawesi and Flores 3 successive faunas can be distinguished. The oldest terrestrial faunas have recorded ages of 2.5 Ma and 0.9 Ma, respectively. On both islands intermediate faunas have a Middle Pleistocene age, while the youngest faunas are sub-recent to Recent.Elephantoids (Stegodon and Elephas) showing various degrees of dwarfing are important constituents in all non-sub-recent/Recent faunas. Their dental, cranial and postcranial remains are described indetail and their taxonomic positions are discussed. A new species (Stegodon sondaari sp. nov.) is described from Flores. Geological/tectonic data and the nature of the impoverished and highly endemic faunas from Sulawesi and Flores both indicate long-lasting isolation from the southeast Asian mainland and from Java.On Flores and probably also on South Sulawesi fauna turnovers with extinction and immigration of elephantoids occurred around the Early to Middle Pleistocene transition. On both islands the total disappearance of elephantoids presumably took place before the onset of the Holocene. On Flores the Middle Pleistocene faunal assemblage is associated with a palaeolithic industry, which is tentatively ascribed to Homo erectus. Early hominids appear to have been able to cross water barriers and successfully colonize Flores as far back as 0.6 Ma ago. They may have been in part responsible for the observed faunal turnover on the island, but alternatively, extinctions may have been caused by a volcanic catastrophe.The existing biostratigraphic framework of Java is discussed and some additions concerning elephantoid taxa are given. Following the emergence of Java above sea-level from the Late Pliocene until c. 1.5Ma, mammalian dispersal to the island was limited. This is illustrated by impoverished faunal assemblages and the occurrence of various dwarfed elephantoids in this time interval, indicating isolated conditions.Further uplift and volcanic activity in combination with episodes of moderate low sea-level led to an increasing accessibility of the Java region until c. 0.8 Ma, though the faunas from this time interval remain somewhat impoverished, suggesting filter dispersal. Stegodon elephantoides is for the first time recorded from Java, originating from a layer correlated with this time interval. Corridor dispersal to Java occurred for the first time at around 0.8-0.7 Ma, and can be tied to marked glacio-eustatic sea-level lowerings starting at 0.8 Ma. This period of low sea-level may also have triggered the faunal turnovers observed on Sulawesi and Flores, by enhancing the chance for a second (overseas) dispersal wave to these islands, and perhaps exchange between Sulawesi and Flores. However, superficial similarities between various island stegodonts must be ascribed to parallel evolution in most cases. Common adaptive trends that can be recognized are dwarfing and increase in hypsodonty.On Java local evolution is documented by the recognition of three successive subspecies of Stegodon trigonocephalus. On Java the extinction of Stegodon and the first recording of Elephas maximus concurs with environmental changes from an open woodland biotope to a rainforest biotope, which took place after the penultimate glacial maximum at 125 ka. On South Sulawesi the Recent fauna presumably entered after the connection with the remaining part of Sulawesi had been established.
De rijke biodiversiteit van het enorme eilandenrijk gelegen tussen het vasteland van zuidoost Azië enhet Australische continent, dat onder andere het gehele Indonesische territorium omvat, is in grotemate te danken aan de complexe geologische geschiedenis. Daarbij heeft isolatie op eilanden eengrote rol gespeeld. Fossiele landvertebraten-voorkomens van de eilanden Java, Sulawesi en Floresvormen het uitgangspunt van de huidige studie. De diverse fossiele faunas van deze eilanden zijn ineen litho- en chronostratigrafisch kader geplaatst, waardoor een bijdrage is geleverd om de complexezoögeografische evolutie van de regio te reconstrueren.Soorten behorende tot de superfamilie der Elephantoidea, waartoe ook de recente olifanten behoren,zijn zeer goed vertegenwoordigd in de fossiele faunas. Vertegenwoordigers van deze groep hebbenzich gedurende de laatste 2,5 miljoen jaar met groot succes kunnen verspreiden binnen het gebied.Fossiele vindplaatsen met één of meerdere Elephantoidea, zijn bekend van de eilanden Sumatra, Java,Borneo, Sulawesi, Sangihe, Flores, Sumba, Timor, Luzon en Mindanao. In een recenter verleden is degrote verscheidenheid aan olifanten grotendeels weer verdwenen, niet alleen regionaal, maar wereldwijd.Vanwege het relatief veelvuldige voorkomen van fossiele olifanten resten, ook op eilanden waarde meeste andere zoogdieren niet konden komen, is de nadruk in dit proefschrift komen te liggen opde olifanten (in de ruimste betekenis van het woord).In het eerste hoofdstuk worden de achtergrond en doelstellingen van het onderzoek geïntroduceerd.Ook wordt de gevolgde taxonomische classificatie van de Proboscidea uiteengezet, gevolgd door eenbeschrijving van de opgravingsprocedures en een verklaring van de gebruikte terminologie en meetmethoden.Het tweede hoofdstuk handelt over een aantal nog niet eerder beschreven elephantoïden resten vanJava, die voor zover mogelijk in het bestaande biostratigrafische kader worden geplaatst. De landfauna-veranderingen die zich gedurende het Pleistoceen op Java hebben afgespeeld waren in grote lijnenbekend, en daarom is het biostratigrafisch kader van Java van groot belang als referentie voor devergelijking met de fauna opeenvolgingen op de eilanden Sulawesi en Flores. Het huidige onderzoeklaat zien dat wat de olifanten betreft de evolutionaire opeenvolging op Java complexer is geweest danaanvankelijk werd aangenomen.Sinds Java gedurende het laat Plioceen ten gevolge van vulkanische en tectonische activiteit boven dezeespiegel is uitgerezen, is er een toename in het totaal aantal soorten grote zoogdieren opgetreden totzo’n 800.000 jaar geleden. Een van de eerste elephantoïden die Java bereikte was Sinomastodon bumiajuensis.Deze mastodont is geassocieerd met de 2 tot 1,5 miljoen jaar oude Satir Fauna, welke slechtseen beperkt aantal soorten omvat, waaronder een nijlpaard, herten en een reuzenschildpad, hetgeenduidt op eiland omstandigheden. Vertegenwoordigers van deze taxa hebben Java waarschijnlijkbereikt door een zeebarrière over te steken (sweepstake route). De ongeveer 1,2 miljoen jaar oude,maar slecht bekende, Ci Saat Fauna was oorspronkelijk gedefiniëerd door het eerste voorkomen opJava van Stegodon. Door de relatieve zeldzaamheid van fossielen uit dit tijdinterval was de overgangtussen de Satir Fauna en de Ci Saat Fauna nauwelijks bekend. Een nog niet eerder beschrevenonderkaak met een ouderdom van tussen de 1,2 en 1,3 miljoen jaar, wordt hier aan Stegodon elephantoidestoegeschreven. Deze zeldzame soort was tot nog toe alleen bekend uit Myanmar. Opvallend isdat enkele meters boven de laag met S. elephantoides nog een reuzenschildpad aangetroffen is, hetgeenerop lijkt te wijzen dat de overgang tussen de Satir en Ci Saat Fauna een geleidelijke is geweest.Twee jongere faunas, de 0,9 miljoen jaar oude Trinil Haupt-Knochenschicht Fauna en de 0,8-0,7miljoen jaar oude Kedung Brubus Fauna, zijn veel beter bekend. De Trinil H.K. Fauna is een enigszinsverarmde Zuidoostaziatische vasteland fauna, met als enige elephantoïde Stegodon trigonocephalus, ter-wijl in de Kedung Brubus Fauna daarnaast ook een echte olifant, Elephas hysudrindicus voorkomt. DeKedung Brubus Fauna is een evenwichtige continentale fauna. De laat-Pleistocene Ngandong Faunalijkt qua samenstelling veel op de Kedung Brubus Fauna, met dit verschil dat vele soorten op subspeciesniveau verschillen, waaronder S. trigonocephalus. Vergelijking van Stegodon materiaal afkomstiguit diverse vindplaatsen, waaronder nog niet eerder beschreven kiezen uit Ngandong, toont aandat er drie opeenvolgende subsoorten van S. trigonocephalus kunnen worden onderscheiden, van oudnaar jong S. t. praecursor (Ci Saat Fauna?), S. t. trigonocephalus (Trinil en Kedung Brubus Faunas) en S.t. ngandongensis subsp. nov. (Ngandong Fauna).Verder is vast komen te staan dat er meerdere verdwergde Stegodon vormen op Java hebben geleefd,maar hun precieze inpassing in de tijdsschaal is tengevolge van onvoldoende stratigrafische gegevensmoeilijk vast te stellen. Belangrijk is ook dat het voorkomen van Elephas maximus op Java voor heteerst met zekerheid kon worden aangetoond. E. maximus moet na de voorlaatste IJstijd in Sundalandzijn onstaan of vanuit zuidoost Azië zijn binnengekomen. Aan het einde van het tweede hoofdstukwordt getracht de belangrijkste fauna-veranderingen op Java te koppelen aan glacio-eustatischezeespiegel fluctuaties en klimaatsveranderingen.In het derde hoofdstuk worden de stratigrafie en terrestrische fauna opeenvolging van Sulawesi behandeld.Zowel fossiele als Recent nog voorkomende landvertebraten zijn in het verleden van ZuidwestSulawesi beschreven. Daarnaast is er ook een paleolithische industrie uit hetzelfde gebied bekend, diemet zogenaamde terrassen geassocieerd zou zijn. Het was echter niet duidelijk of de diverse fossieletaxa dezelfde ouderdom hadden, en of de stenen werktuigen al dan niet met primaire fossielvoorkomensgeassocieerd waren. Ook bestond er onenigheid over de manier waarop de landvertebratenop Sulawesi terecht waren gekomen, over zee of via voormalige landverbindingen. Om die laatsteprobleemstelling te benaderen is een uitgebreide literatuurstudie gemaakt van de regionale geologieen tektoniek, waaruit blijkt dat de Makassar Straat gedurende het Midden Eoceen is ontstaan. Mogelijkis er tijdens het Oligoceen nog een landverbinding geweest, maar voor alle latere verspreidingen naarSulawesi moeten er een of meerdere zeebarriéres zijn genomen. Ook voormalige landverbindingentussen Noord Sulawesi en Mindanao zijn zeer onwaarschijnlijk. Het huidige stratigrafisch en geologischonderzoek heeft uitgewezen dat er geen sprake is van terrassen maar dat de fossielhoudende lagen,behorende tot de fluvio-estuariene Beru Member van de Walanae Formatie, locaal is opgeheven in eenbreukbegrensd gebied, zonder dat er noemenswaardige scheefstelling is opgetreden. Dit impliceert datde paleolithische werktuigen, indien afkomstig uit deze afzettingen, een veel grotere ouderdom kunnenhebben dan de Laat Pleistocene ouderdom die tot nog toe werd aangenomen.De samenstelling van de terrestrische fauna uit de Beru Member, Walanae Fauna genoemd, duidt opeiland-omstandigheden. De oudste, beschreven associaties van de Walanae Fauna zijn afkomstig uithet Boven Plioceen en zijn ca. 2,5 miljoen jaar oud, hetgeen ouder is dan de oudste (ei)land fauna vanJava. De jongste lagen met Walanae Fauna hebben waarschijnlijk een vroeg-Pleistocene ouderdom. Defauna bevat de volgende elementen: een uitgestorven dwergolifant (“Elephas” celebensis), een dwergstegodont(Stegodon sompoensis), een reuzeschildpad (Geochelone atlas), een varkenssoort (Celebochoerusheekereni), Crocodylus spec. en Trionychidae gen. et sp. indet. Fragmentarische oppervlakte vondstenwijzen erop dat in een later stadium mogelijk ook een grote Stegodon soort deel uitmaakte van deWalanae Fauna. Aangetoond kon echter worden dat de Walanae Fauna géén grote zoogdiersoortenbevat die recent nog voorkomen. De Walanae Fauna leefde geruime tijd geïsoleerd en vast is komente staan dat bij het meest voorkomende element, Celebochoerus, in de loop der tijd een verkorting vande metapoden is opgetreden als aanpassing aan het eilandmilieu.Onverwachts is nog een tweede, jongere fossiele fauna ontdekt, die Tanrung Fauna is genoemd naarde Tanrung Formatie waarin deze fauna is aangetroffen. In de Tanrung Formatie zijn in situ fossielenvan een middelgrote tot grote stegodont (Stegodon sp. B) aangetroffen en van een kleinere Celebochoerussoort. Behalve het laatstgenoemde taxon zijn geen resten van andere elementen uit deWalanae Fauna in de Tanrung Formatie gevonden. De Tanrung Fauna heeft een (geschatte) middenPleistocene ouderdom. Oppervlakte vondsten in het gebied waar de Tanrung Formatie dagzoomtomvatten resten van Anoa sp. en van Sus celebensis (beide Recent nog voorkomende soorten), en vaneen geavanceerde hoogkronige Elephas soort, waarvan waarschijnlijk alleen de laatsgenoemde uit deTanrung Formatie afkomstig is. De andere soorten zijn zeer waarschijnlijk afkomstig uit jongerekustafzettingen, die met een erosief contact op de Tanrung Formatie zijn afgezet. Vermoedelijkgedurende het Vroeg of Midden Pleistoceen is er een fauna omslag in Sulawesi opgetreden. In iedergeval moeten er meerdere, in de tijd verspreide elephantoïden immigraties naar Zuidwest Sulawesizijn geweest. Stegodon sp. B is ook aangetroffen op het eilandje Sangihe. Vermoedelijk pas in het LaatPleistoceen zijn olifanten geheel uit Zuidwest Sulawesi verdwenen. De Recente fauna van grotezoogdieren, inclusief Babyroussa en Anoa, is waarschijnlijk vanuit Centraal Sulawesi naar ZuidwestSulawesi verspreid nadat een landverbinding tussen beide delen tot stand was gekomen. Babyroussaleefde mogelijk al sinds het Oligoceen in Centraal Sulawesi.Het vierde hoofdstuk behandelt de paleontologie van de elephantoiden van Sulawesi. Stegodon sompoensisis een verdwergde eilandvorm en behoort tot de groep stegodonten waartoe ook S. trigonocephalus(Java) en S. ganesa (Indiase sub-Continent) behoren. “Elephas” celebensis is eveneens eendwergvorm, die over een aantal unieke schedelkenmerken beschikt. Deze soort stamt mogelijk af vande vroegste E. planifrons populaties van het vasteland, maar kan ook uit meer archaïsche Elephantidaezijn ontstaan. Stegodon sp. B is een middelgrote tot grote stegodont, die mogelijk nauw verwant is aanS. florensis uit vroeg midden-Pleistocene afzettingen op het eiland Flores. De identiteit van enkeleschaarse Elephas resten kon niet nader worden vastgesteld, maar duidelijk is dat deze olifant nauwverwant moet zijn geweest met een geavanceerde midden- of laat-Pleistocene Elephas soort, waarschijnlijkE. namadicus. Hiermee is het aantal elephantoïden soorten die ooit op Sulawesi hebben geleefd opminimaal 4 soorten komen vast te staan.Het vijfde hoofdstuk richt zich op de stratigrafie en fauna opeenvolging van het fossielrijke SoaBekken in Flores. De ± 0,9 miljoen jaar oude Fauna A afkomstig uit de onderste Member A van de OlaBula Formatie, bevat een dwerg stegodont (Stegodon sondaari sp. nov.), een reuzen landschildpad(Geochelone sp.), een kleine krokodil en resten van de recent nog voorkomende Komodo varaan(Varanus komodoensis). De jongere Fauna B is geassocieerd met de fluviatiele Member B van de OlaBula Formatie en heeft een ouderdom van tussen de 0,7 en 0,6 miljoen jaar. Fauna B bevat geen S. sondaarinoch reuzenschildpad, maar wel een middelgrote stegodont (S. florensis) en een reuzenrat (Hooijeromysnusatenggara). Zowel Fauna A als Fauna B duiden wederom op geïsoleerde eilandomstandigheden. De faunaomslag op Flores vertoont gelijkenis met die van Zuidwest Sulawesi intiming en karakter. Op beide eilanden treden belangrijke faunaveranderingen op rond de overgangvan Vroeg naar Midden Pleistoceen en komen de kleinste dwerg elephantoïden voor in de ouderefauna. Bewezen kon worden dat op Flores de jongere Fauna B geassocieerd is met een primitievelithische industrie. Deze kan gezien de hoge ouderdom (gebaseerd op paleomagnetische analyse) nietworden toegeschreven aan Homo sapiens; gedacht wordt dan ook dat Homo erectus de maker van dewerktuigen is geweest. Deze gegevens suggereren dat H. erectus in staat zou zijn geweest om zeestratenover te steken. Tot nog toe werd algemeen aangenomen dat H. sapiens de eerste zeevaarder was,maar uit de huidige gegevens zou afgeleid kunnen worden dat H. erectus al zo’n half miljoen jaareerder de zee is opgegaan. Dit zou weer verstrekkende gevolgen hebben voor interpretaties betreffendede technische en geestelijke vermogens van H. erectus. Hoewel voorzichtigheid is geboden, is dehoge ouderdom van de artefact-houdende laag inmiddels al wel bevestigd door middel van alternatievedateringsmethoden.Het zesde hoofdstuk geeft een paleontologische beschrijving van de stegodonten uit Flores. Stegodonsondaari is de kleinste tot nu toe bekende dwergstegodont en verschilt duidelijk van dwergstegodontenuit Sulawesi en Timor. Kiezen van S. sondaari vertonen enkele primitieve kenmerken, hetgeen suggereertdat deze dwergsoort afstamt van een archaïscher soort dan S. trigonocephalus. S. sondaari kanmogelijk al sinds het laat Plioceen op Flores vertegenwoordigd zijn geweest. Geconcludeerd wordtdat de stegodont uit fauna B van Flores op soortsniveau verschilt van S. trigonocephalus, en als S. florensisaangeduid dient te worden. Kiezen van S. florensis vertonen overeenkomsten met die van Stegodonsp. B uit de Tanrung Fauna van Sulawesi.De hoofdstukken 7 en 8 geven een aantal paleozoogeografische en paleobiologische beschouwingennaar aanleiding van de resultaten op de diverse eilanden. De elementen van de Walanae Fauna zijnwaarschijnlijk vanuit het Indiase Subcontinent via Burma en Sundaland in Zuidwest Sulawesi terechtgekomen door de zeeëngte tussen Zuidwest Sulawesi (dat toen een apart eiland vormde) en het Sundaplatover te steken. Dit is waarschijnlijk tijdens het Laat Plioceen gebeurd, toen belangrijke glacio-eustatisch-bepaalde zeespiegel laagstanden optraden waardoor de totaal overzee te overbruggen afstandengeringer waren dan in de recente situatie. De oudere landfaunas van Java zijn eveneens voorhet grootste deel afkomstig uit het Indiase Subcontinent. Aanvankelijk is het verspreidingsmechanismenaar Java sweepstake- en filter-verspreiding geweest. Vanaf het Sunda Plat konden sommigesoorten zich verder verspreiden naar Sulawesi. De latere maximale verspreiding naar Java vondplaats via een corridor rond 0,8 miljoen jaar geleden. In Japan en Taiwan komen dan ook voor heteerste continentale faunas binnen, terwijl in Sulawesi en Flores slechts enkele nieuwe soorten binnenkomen.Deze observaties zijn in overeenstemming met gegevens omtrent eustatische zeespiegelfluctuaties,waaruit blijkt dat vanaf 0,8 miljoen jaar geleden de zeespiegel gedurende langere periodeslager kwam te liggen dan in het tijdsinterval daarvoor, waardoor het Sunda platform meerdere malengeheel droog kwam te liggen. Waarschijnlijk was deze laagstand ook bepalend voor de fauna-omslagenop de eilanden Sulawesi en Flores. Het is zeer wel mogelijk dat de voorouder populatie van S. florensisniet vanuit Java maar vanuit Sulawesi op Flores terecht is gekomen, hoewel een landverbindingtussen beide eilanden uitgesloten kan worden.Op Java valt pas in de laat-Pleistocene Punung Fauna een duidelijke relatie met zuid-Chinese faunaste onderscheiden. Wederom vond verspreiding via een corridor plaats. Vooralsnog zijn er geen eenduidigeaanwijzingen dat Chinese elementen ook Sulawesi en Flores hebben bereikt via de Philippijnen.Het is echter niet uit te sluiten dat een of meerdere elephantoïden de route Philippijnen-Sulawesi-Flores hebben gevolgd.Vast staat dat de dwerg elephantoïden van Sulawesi, Flores en Timor verschillen op soortsniveau.Deze vormen moeten onafhankelijk van elkaar onstaan zijn, terwijl oppervlakkige gelijkenissen kunnenworden toegeschreven aan paralelle evolutie. Zo lijkt er naast de algemene trend van verdwergingook een evolutionaire trend te zijn geweest die er toe leidde dat de dwarsrichels op de kiezen vaneiland stegodonten geleidelijk aan hoogkroniger werden, waardoor in sommige gevallen sterkegelijkenis met de kiezen van de eerste echte olifanten optrad. Deze toename in hypsodontie moetgezien worden als een aanpassing aan het eilandmilieu. Algemeen wordt gedacht dat verdwergingvan grote zoogdieren op eilanden in de eerste plaats het gevolg is van de combinatie van een geringervoedselaanbod en het ontbreken van carnivoren. De kleinste elephantoïde uit de regio, Stegodon sondaari,had een geschat volwassen lichaamsgewicht van tussen de 200 en 500 kg. Opvallend is dat deelephantoïden uit de jongere, midden-Pleistocene eilandfaunas van Flores en Sulawesi weliswaarkleiner zijn dan vasteland soorten, maar desalnietemin grotere afmetingen hebben dan de verdwergdevormen uit de voorafgaande laat-Pliocene — vroeg-Pleistocene faunas. Op Flores kan deze geringereverdwerging van de “tweede golf” elephantoïden mogelijk toegeschreven worden aan de aanwezigheidvan een warmbloedige predator, namelijk Homo. Voor Sulawesi zijn er vooralsnog geenaanwijzingen in die richting, tenzij in de toekomst bewezen zou kunnen worden dat de paleolithischewerktuigen van de Tjabenge Industrie dezelfde ouderdom hebben als de Tanrung Fauna.Een leeftijdsprofiel van S. sondaari gebaseerd op de slijtpatronen van kiezen toont aan dat deaangetroffen fossiel-accumulatie het gevolg is van niet-selectieve massale sterfte. Combinatie met sedimentologischegegevens duidt erop dat de massale sterfte het gevolg moet zijn geweest van eenvulkanische uitbarsting. De reconstructie van leeftijdsprofielen voor andere associaties van elephantoïdenleidde tot minder eenduidige resultaten.In het laatste hoofdstuk worden een aantal conclusies die voortvloeien uit het huidige onderzoeksamengevat.
South Sulawesi, situated at the junction of three major plates and with an almost complete Tertiary sequence, is an ideal location in which to study syntectonic sedimentation. Redeposited carbonate facies of the lower/middle Eocene to middle Miocene Tonasa Limestone Formation in the Barru area prove to be reliable indicators of tectonic activity. South of the Barru area contemporaneous carbonate sediments formed on a relatively stable shallow-water platform, known as the Tonasa Carbonate Platform. Redeposited carbonate facies and interbedded marls from the Barru area are described and interpreted. The immaturity and provenance of clasts indicate that the redeposited facies were derived from the faulted northern margin of the Tonasa Carbonate Platform. Three main phases of faulting are indicated by redeposited facies: late Eocene to early Oligocene, middle Oligocene and early to middle Miocene. This is consistent with other outcrop and seismic data from the region and with the inferred plate tectonic situation during the Tertiary. -from Authors
This paper is part of the special publication Petroleum geology of Southeast Asia (eds A.J. Fraser, S.J. Matthews and R.W. Murphy). The Kutai Basin, Kalimantan, is one of several large Tertiary basins which opened during the mid- to late Eocene in Borneo. Extensional tectonics are responsible for basin formation, and not crustal flexure as has been suggested previously. Extensional faulting did, however, occur within a general foreland setting located to the south of the late Cretaceous/Palaeogene Central Kalimantan fold belt. The basin post-dates late Cretaceous/early Tertiary orogenic activity which affected the Central Kalimantan foldbelt and formed several upper Cretaceous granites. The Palaeogene stratigraphy of the basin includes basal conglomerates, shallow marine clastics and minor clastics and thick sequences of bathyal marine shales. Neogene stratigraphy is dominated by deltaic clastics and carbonate platforms. Several phases of Tertiary igneous activity are seen intruded into and interbedded with Tertiary sediments of the Kutai Basin. Three suites are recognized and have been variously interpreted as the products of melting of an orogenic root, extensional driven melting and/or subduction related melting. We review Tertiary sedimentation in the basin and propose a new model which relates the formation of the Kutai Basin to the opening of Celebes Sea and collapse of an uplifted Late Cretaceous/Palaeogene orogenic belt.
The Kerendan carbonate platform (Oligocene Berai Limestone) covers a subsurface area measuring approximately 11 by 16 km in the westernmost Kutei Basin, Central Kalimantan. Aggradation of the Kerendan platform occurred during a major Oligocene transgression, and is contemporaneous with aggradation and backstepping of the Barito shelf margin which was located approximately 30 km to the south. The Kerendan platform is approximately 1,000 m thick, and comprises three aggrading seismic sequences identified by the downlap of basinal strata at the platform margin and downlap of transgressive strata within the platform. Carbonate deposition started in the Late Eocene, and ended when the upper limestone sequence drowned and was covered with shale in the Late Oligocene (approximately 28.6 Ma). Three depositional areas can be distinguished in seismic sections: (1) a platform interior (lagoon); (2) a slightly raised platform rim (1–2 km wide); and (3) a basinward-dipping platform margin and slope. The margin of the platform is identified by inflections on the seismic profiles where the relatively flat platform top begins to slope basinward.
Cenozoic equatorial carbonate production was at its most extensive and diverse in the seas of Southeast Asia, yet the carbonates of this region remain poorly documented. This paper presents the first published review of carbonate deposition during the Cenozoic, collating sedimentological data for carbonate successions throughout the region. Current models of warm-water carbonate platform evolution, sedimentation and facies distribution, inspired by studies of the classic (sub)tropical areas, provide inadequate analogues for the evaluation of modern or Cenozoic equatorial carbonates in Southeast Asia. The equatorial carbonates differ in being dominated by bioclasts. Coated grains and associations with evaporites or dolomites are rare. The carbonate systems occur in a range of depositional settings which were often affected by coeval tectonism, siliciclastic input or volcanism. An understanding of the carbonate depositional environments, spatial facies distributions and controls on deposition and diagenesis is essential in order to characterize equatorial carbonate development and to evaluate their considerable economic potential.
Sulawesi and Borneo are located in the middle of the Indonesian Archipelago, an area which has been extremely tectonically active throughout the Cenozoic. This paper compiles current knowledge on the geology and palaeogeography of this complex region and includes the first attempt to synthesise palaeogeographic data onto plate tectonic reconstructions. Construction of palaeogeographic maps helped to identify some of the strengths and weaknesses of current plate tectonic models for the region, thereby highlighting areas where further geological research is required. Palaeogeographic maps presented, using plate tectonic reconstructions as a base, illustrate the evolution of Borneo and Sulawesi and highlight important changes in the environment during the Cenozoic. The Tertiary geological history of eastern Borneo and Sulawesi is inextricably linked to the progressive accretion of continental and oceanic material from the east, onto the eastern margin of Sundaland, and to the resultant development of volcanic arcs. Large tracts of western Sulawesi, eastern Borneo, the East Java Sea and the Makassar Straits formed an extensive basinal area throughout much of the Tertiary. Implications for plate tectonics, exploration for natural resources and biogeography are discussed from the palaeogeographic reconstructions of Sulawesi and Borneo.
The margin of Enewetak Atoll contains 1,260 to 1,405 m of Cenozoic carbonates above a volcanic basement. Previous biostratigraphic studies on two deep wells (E1 and F1) yielded conflicting results on the ages of Tertiary strata on Enewetak, and on the presence of Oligocene strata. Strontium-isotope ratios support relatively continuous carbonate sedimentation from late Eocene to early Miocene (23 Ma). Carbonate deposition on the atoll margin started with rapid aggradation during much of the late Eocene followed by gradual seaward progradation of depositional facies during the latest Eocene, Oligocene, and early Miocene. The only distinct break in sedimentation from late Eocene to early Miocene was observed at ~850 m in the E1 well. Here an unconformity formed by subaerial exposure separates backreef, upper Eocene grainstones from lower Oligocene carbonates. No contemporaneous subaerial exposure surface and unconformity were observed in the F1 well because correlative rocks were deposited in a slope environment. Extensive diagenesis occurred in upper Eocene, Oligocene, and lower Miocene strata at the atoll margin where sea water circulated through in response to thermal convection and tidal pumping. The main diagenesc processes are (1) aragonite dissolution, (2) radiaxial calcite cementation, (3) compaction in slope deposits, and (4) dolomitization. Aragonite dissolution is pervasive below 375 m in the F1 well. Radiaxial calcite cement is common at 375-825 m in the F1 well. Compaction-related fracturing and pressure solution are common in poorly cemented packstones and grainstones deposited in a slope environment and now buried more than 1,100 m deep. Dolomite is common in slope carbonates at ~1,320 m in the F1 well and in reefal carbonates at 1,245 m in the E1 well. Stable carbon- and oxygen-isotope data support formation of radiaxial calcite and dolomite in cool sea water. Radiaxial calcite cement and dolomite have distinctly higher 87Sr/86Sr ratios than does adjacent depositional carbonate. Strontium-isotope ratios of radiaxial calcite cements indicate precipitation at burial depths of 100-350 m. The absence of meteoric cements and association of radiaxial calcite cement with aragonite dissolution suggest that aragonite dissolution also occurred in moderately deep sea water. Strontium-isotope ratios in dolomites indicate dolomitization by sea water at burial depths greater than 950 m. Marine diagenesis is dependent on the saturation state of sea water relative to aragonite, calcite, and dolomite. Shallow sea water, supersaturated with respect to aragonite and high-magnesium calcite (HMC), precipitates aragonite and HMC. Moderately deep sea water (undersaturated with respect to aragonite and HMC, super-saturated with respect to low-magnesium calcite-LMC) dissolves aragonite, converts HMC to LMC, and precipitates LMC (including radiaxial calcite). Deep sea water (under-saturated with respect to calcite, supersaturated with respect to dolomite) dissolves calcite and precipitates dolomite. The intensity of marine diagenesis depends on the amount of sea water circulating through the platform or atoll margin.
Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically
related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level
events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new
generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past
250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop
a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented
in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach
and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals,
are presented.
Previous studies of test shape and distribution trends of reef-associated Foraminiferida provide the basis for a model of foraminiferal distribution in Cenozoic carbonate depositional facies. The model predicts distributions of foraminifera in Wilson's Standard Carbonate Facies. This model, when tested on thin sections cut from lower Miocene carbonate cores from four Philippine wells, enhanced the paleoenvironmental analysis and inerpretation developed using standard petrographic techniques. The model is based upon recognition of three major groups of easily recognizable foraminifera: 1) thin, larger, rotaliine foraminifera plus planktonics, 2) ovate, larger rotaliines, and 3) miliolines and smaller rotaliines. The relative percentages of these environmentally diagnostic foraminifera, when plotted on triangular diagrams, provide graphic indication of paleoenvironment. -from Authors
We improved upper Eocene to Oligocene deep-sea chronostratigraphic
control by integrating isotope (87Sr/86Sr,
δ18O, δ13C) stratigraphy and
magnetostratigraphy. Most previous attempts to establish the timing of
isotope fluctuations have relied upon biostratigraphic age estimates
which have uncertainties of 0.5 to over 4.0 m.y. Deep Sea Drilling
Project (DSDP) Site 522 contains the best available upper Eocene to
Oligocene magnetostratigraphic record which allows first-order
correlations of isotope records (87Sr/86Sr,
δ18O, δ13C) to the Geomagnetic
Polarity Time Scale (GPTS). Empirical calibrations between the
87Sr/86Sr of foraminifera and magnetochronology at
Site 522 allow more precise correlation of "unknown" samples with the
GPTS. For example, shallow water and high-latitude sections may be tied
into the deep-sea record. Sr-isotope stratigraphic resolution for the
latest Eocene to Oligocene is approximately 2 m.y.
Carbonate platform drowning events are recorded in Upper Jurassic-Lower Cretaceous carbonates of the Baltimore Canyon area, offshore US East Coast, and lower Miocene carbonates of the Pearl River Mouth Basin, offshore People's Republic of China. Cursory examination of seismic data from both areas would indicate that the platforms fit the classic definition of a drowning unconformity. However, detailed lithologic and paleontologic data indicate that the depositional/erosional hiatuses vary widely in each area, from 0-25 m.y. in the Baltimore Canyon area, to a condensed section with no hiatus in the Pearl River Mouth Basin. The sedimentary sequence produced during drowning in both areas is gradational with underlying shallow platform carbonates and, in some places, overlying deeper marine limestones and shales. The generalized facies models proposed for drowning events suggest that they may appear as instantaneous or gradual changes in geologic and seismic data. Because of this resolution problem, a distinction should be made between seismically and geologically defined unconformity surfaces. The geologic characteristics of drowning events on carbonate platforms include a gradational lower (and sometimes upper) contact, chemical sedimentation (glauconite, phosphate), open-marine shelf sediments, and a variable hiatus at the upper boundary. Data from isolated open-ocean atolls (Pearl River Mouth Basin) indicate that they respond differently to drowning, showing an asymmetric decrease in shallow platform environments as drowning occurs. Proper recognition by a geoscientist of the seismic and geological characteristics of drowning events can lead to better reservoir and seal estimates, and the correct reconstruction of the depositional, tectonic, and eustatic histories of an area.
Precise measurements of 786 marine carbonate, evaporite, and phosphate
samples of known age provide a curve of seawater
87Sr/86Sr versus geologic time through the
Phanerozoic. Many episodes of increasing and decreasing values of
87Sr/86Sr of seawater have occurred through the
Phanerozoic. The Late Cambrian Early Ordovician seawater ratios are
approximately equal to the modern ratio of 0.70907. The lowest ratios,
˜0.7068, occurred during the Jurassic and Late Permian. The
configuration of the curve appears to be strongly influenced by the
history of both plate interactions and seafloor spreading throughout the
Phanerozoic. The curve provides a basis for dating many marine
carbonate, evaporite, and phosphate samples. Furthermore, diagenetic
modifications of original marine 87Sr/86Sr values
are often interpretable. Analysis of 87Sr/86Sr
data, therefore, may provide useful information on regional diagenetic
patterns and processes. All of the Cenozoic samples and some of the
Cretaceous samples are from Deep Sea Drilling Project (DSDP) cores. With
the exception of the DSDP samples, the curve was constructed only from
samples containing at least 200 ppm Sr and not more than 10% dilute acid
insoluble material. All measurements are made by comparison with
standard SrCO3 (NBS SRM 987) for which a
87Sr/86Sr of 0.71014 is assumed. Precision is
estimated to be ± 0.00005 at the 95% confidence level. Measured
ratios of 42 modern marine samples average 0.70907, with a standard
deviation of 0.00004. *Present addresses: (Denison) Suite 616, One
Energy Square. 4925 Greenville Avenue, Dallas, Texas 75206; (Nelson)
2516 West Five Mile Parkway, Dallas, Texas 75233
Sr isotopic analyses of well-preserved portions of Permo-Carboniferous brachiopods distributed globally confirm the general shape of the Sr isotope age curve established by previous workers for this time interval. There is little variation between the Sr isotopic composition of unaltered portions of brachiopods and that of portions of the same shell interpreted to be diagenetically altered (based on cathodoluminescence, elemental, and stable isotopic data). However, the Sr isotopic composition in diagenetically altered micritic matrix adjacent to the shell is more radiogenic. The Sr isotopic composition in the unaltered portions of calcitic megafossils has potential as a stratigraphie tool.
Differences among depositional systems, here called depositional bias, strongly influence sequence patterns. Siliciclastics and shallow-water carbonates, for instance, shed most of their sediment during opposite phases of a sea-level cycle (lowstand shedding and highstand shedding, respectively). Furthermore, the two systems generate their own, system-specific relief on the sea floor, disperse their sediment load along different avenues and differ in the way they are deactivated: reefs and carbonate platforms can be drowned, whereas siliciclastic deposition can be shut off and renewed at any depth. As a consequence of these differences, pronounced unconformities (drowning unconformities) develop where carbonate platforms are terminated and buried by siliciclastics (the siliciclastic-to-carbonate transition tends to be more gradual). Drowned platforms and drowning unconformities appeared world-wide in great abundance in the Miocene, Cretaceous (Valanginian-Turonian), Jurassic (Toarcian) and Devonian (Frasnian/Famennian). Examples of drowning unconformities interpreted as sequence boundaries, include those of the Early Cretaceous platforms off New Jersey and off Morocco, the mid-Cretaceous unconformity in the Gulf of Mexico and Miocene unconformities on top of reefs in the Far East.
The stable oxygen isotope record for the Cenozoic is characterized by a series of large third-order steps of +1 per mil superimposed on a long-term second-order trend. This second-order trend accounts for a δ18O change of nearly +4 per mil from the early Eocene into the Neogene. The second- and third-order changes in the δ18O signal are driven primarily by a combination of glacio-eustatic sea-level and ocean paleotemperature changes. These changes are global responses to evolving circulation and climate patterns. Timing of the δ18O events is in good agreement with the seismically defined changes in the coastal-onlap curve (Vail and others, 1977). Agreement in the timing of events supports a common mechanism, perhaps that glaciation is apparent throughout much of the record and certainly intensified beginning in the Neogene. -from Author
Neogene chronology and chronostratigraphy
- W A Berggren
- D V Kent
- J J Flynn
Berggren, W.A., Kent, D.V. & Flynn, J.J., 1985.
Neogene chronology and chronostratigraphy, In:
Snelling, N.J. (ed.), The Chronology of the Geological
Record. Geological Society Memoir 10, 141-195.
The Cainozoic Globigerinida, 3 vols
- W H Blow
Blow, W.H., 1979. The Cainozoic Globigerinida, 3
vols.: E.J. Brill, Leiden, 1413pp.