1. It is a myth that only glacio-eustatic driven processes can change relative sea level by more than 100m in less than a million years
   • Miller et al. (2005), amongst others, stated “Eustatic changes with amplitudes of 10s of meters in less than 1 My … because ice-volume changes are the only are the only known means of producing such large and rapid changes.” The key word to note here is eustatic. People have read this or similar statements and forget that relative sea level changes can change as fast and as much as this, over surprisingly large “local” areas. For example, in north Sumatra and west Thailand (some 50,000 sq. km.) the relative sea level rose (i.e. the basement subsided rapidly) changing deposition from coastal plain or inner neritic to bathyal settings (almost 2000 m in some wells according to Esso stratigraphers) in the mid Oligocene (Lunt, 2019a). Similar sudden subsidences are known in the South China Sea also in mid Oligocene times, on the Oligo-Miocene boundary and in the west near the end of the Early Miocene (Lunt 2019b), and in the Makassar Straits in the Eocene (Lunt and van Gorsel, 2013)
2. The correlatable mega-sequence boundaries in SE Asia can have much greater relative sea level (rsl) change than proposed eustasic events
   • As with point 1, this comment applies to very rapid tectonic changes, not the ponderously slow movements that workers from tectonically passive areas imagine are overprinted by faster eustatic variation.
   • The examples given above are illustrations of where, in less than a million years, new accommodation space of many hundreds of metres was created (see MS-1 geohistory plot in Lunt and van Gorsel; 2013). The new sediment fill can be so great it exaggerates the creation of accommodation space by isostatic loading, and it is hard to proportion the true tectonic subsidence vs loading. These kinds of extreme problems do not crop up in studies of eustatic sea level change
3. The correlatable mega-sequence boundaries of SE Asia have mappable variation in rsl magnitude, with focal areas related to their tectonic causes
4. The correlatable mega-sequence boundaries have different timing to the proposed glacio-eustatic sequence boundaries
   • The largest Cenozoic eustatic sea level fall proposed was in mid-Oligocene times; roughly 28-29 Ma. However, as many authors have noted (e.g. Saller et al. 1993) the Berai Limestone of S. Kalimantan was deposited throughout this age in a continuous inner neritic setting, showing no stratigraphic indication of a sea level fall, in outcrops or well samples. In many areas (South China Sea, north Sumatra, parts of east Java) this was a time of major sea level rise (c. 28 Ma just after the Chiloguembelina cubensis datum, 28.4 Ma).
5. While cyclical or sinusoidal variation in stratigraphic properties can often be interpreted in some data, or derivatives such as pattern of coarsening and fining upwards on gamma logs, there is no unique, allocyclic, profile of sea level change that can be recognised and correlated around SE Asia**
   • Allocyclic means driven by processes larger than basin scale, such as eustasy or large, regional epeirogenic crustal movements. Such changes would have roughly even sea level changes expressed over a wide area. The opposite, autocyclic processes affect a local number of basins or a basin, such as the lateral lobe-switching of a major delta in one basin, or multi-basin subsidence in one area due to some tectonic change as a break-up unconformity in the South China Sea. These changes produce the geographically variable change in relative sea level mentioned in item 3
   • The only papers claiming to have identified global signatures in Sundaland (e.g. Bartek et al., 1991) have been re-dated and found to be a false, forced, correlation of a simple sinusoidal signature (Luan and Lunt, 2021)
6. There is an exception to the comment (5) in the mid Pliocene of many SE Asia basins (a section above interest to most exploration wells) where there is the correlatable beginning of rapid changes in sedimentary facies. From the Malay basins, eastern Java and the Brunei delta the Late Pliocene and Pleistocene samples have coal and inner neritic bioclasts concentrated in some samples, alternative with deep middle neritic faunas in the next. In the Malay Basin apparently fluvial channels can be interpreted interbedded with moderately deep marine clays (see Miall, 2002; Lunt 2021). The rapid fluctuation of contrasting lithofacies and faunas correlates with the onset of the modern ice ages and the growth of the northern hemisphere ice sheets
7. In SE Asia the megasequence boundaries are extensional and widespread in the later Eocene through Early Miocene, as the basins around the region were growing and subsiding (increasing sea level, contrary to a proposed gradual global sea level fall). However from within the later Early Miocene to Recent the megasequence boundary are mostly interruptions to more gradual compressive effect, and generally cover smaller areas, with greater geographic variation in expression (e.g. the Deep Regional Unconformity and Shallow Regional Unconformity within the longer lasting Sabah Orogeny in northwest Borneo and south Palawan)
8. The evidence-based tectono-stratigraphic framework is predictive and testable. As noted in item 5, proposed eustatic controls on medium to large scale sedimentation in SE Asia have not been predictive, other than the tautological (ie. there may be low stand turbidites or a vaguely defined age in deep marine facies).

References

Bartek, L. R., Vail, P. R., Anderson, J. B., Emmet, A., & Wu, S., 1991. Effect of Cenozoic ice sheet fluctuations in Antarctica on the stratigraphic signature of the Neogene. Journal of Geophysical Research 96(B4), 6753-6778

Luan, X. and Lunt, P. 2021. Eocene to Miocene stratigraphic controls in the far East Java Sea: Implications for stratigraphic studies Marine Geology

Lunt, P., 2019a. Partitioned transtensional Cenozoic stratigraphic development of North Sumatra. Marine and Petroleum Geology 106, 1-16

Lunt, P., 2019b. A new view of integrating stratigraphic and tectonic analysis in South China Sea and north Borneo basins. Journal of Asian Earth Sciences 177, 220-239

Lunt, P., 2021. A reappraisal of the Cenozoic stratigraphy of the Malay and West Natuna Basins. Journal of Asian Earth Sciences: X 5,

Lunt, P., & van Gorsel, J. T., 2013. Geohistory analysis of South Makassar. Berita Sedimentologi 28, 14-52

Miall, A. D., 2002. Architecture and sequence stratigraphy of Pleistocene fluvial systems in the Malay Basin, based on seismic time-slice analysis. AAPG Bulletin 86(7), 1201-1216

Miller, K. G., Kominz, M. A., Browning, J. V., Wright, J. D., Mountain, G. S., Katz, M. E., Sugarman, P. J., Cramer, B. S., Christie-Blick, N., & Pekar, S. F., 2005. The Phanerozoic record of global sea-level change. Science 310, 1293-1298

Morley, R. J., Hasan, S. S., Morley, H. P., Jais, J. H. M., Mansor, A., Aripin, M. R., Nordin, M. H., & Rohaizar, M. H., 2020. Sequence biostratigraphic framework for the Oligocene to Pliocene of Malaysia: High-frequency depositional cycles driven by polar glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology 561, 110058

Morley, R. J., & Swiecicki, T., 2015. Correlation across the South China Sea using VIM transgressive-regressive cycles. AAPG Search & Discovery #90236

Saller, A., Armin, R., Ichram, L. O., & Glenn-Sullivan, C., 1993. Sequence stratigraphy of aggrading and backstepping carbonate shelves, Oligocene, Central Kalimantan, Indonesia. In R. G. Loucks & J. F. Sarg (Eds.), Carbonate sequence stratigraphy: recent developments and applications. AAPG Memoir 57, 267-290.