As Posamentier and others predicted…

Something I like to stress in teaching is that I do not disagree with the founders of eustatic sequence stratigraphy. Below is an extract from  Posamentier et al. (1988) declaring the assumptions required to apply their method:

Some parts highlighted in yellow do not apply to many basins in SE Asia. But not all basins. The Pattani – Malay – West Natuna basin complex is relatively stable, and many of the comments highlighted in yellow still apply there (but then these basins are just a concentrated proximal part of a whole sedimentary clinoform that debouches into the South China Sea, and the South China Sea is subject to tectonic control, as shown in Lunt 2021a; with knock-on tectonic effects reaching into the Malay Basin). The Mahakam Delta in east Kalimantan is a more complete clinoform and a thick, stable sedimentary system – but only after an N8 inversion / uplift event. Before that time it had a much more dynamic history.

The text in yellow:

• In many locations around SE Asia the rate of sea-floor subsidence has been highly variable through time and varying laterally, as demonstrated by geohistory plots (see Lunt 2019a, b in North Sumatra, East Java; Lunt and van Gorsel, 2013 in the Makassar Straits)

• Total subsidence does not always increase in a basinwards direction; East Java, Sarawak (Lunt and Madon, 2017) and many many more. The proximal-distal direction can shift many times during the depositional history. This was clearly recognised by the early Shell workers in Sarawak and shown on their palaeogeography maps (reproduced in Hutchison, 2005) and also similar maps by Petronas in Madon (1999)

• Sediment supply does not remain constant. Again many examples around Sundaland. This especially true from the mid Early Miocene as compression and uplift became more common. Also centers of uplift migrated considerable through time.

• The eustatic sea-level change is curvilinear, approaching sinusoidal – but the relative sea-level change at any location around SE Asia can be quite wild. Lunt and van Gorsel (2013) and some new papers in press, the Sarawak review, and South China Sea “MMU” papers (Lunt , 2019c). Not many people draw geohistory plots for SE Asia, so forgive the self-references.

So yes, the last comment highlighted applies: local factors must be considered, and in the case of, I would say, the majority of SE Asian basins these absolutely dominate over eustatic effects. As pointed out in other posts, a eustatic curve in SE Asia cannot be determined from raw data, unless you look for the very small (?4^th order) fluctation as proposed by Morley et al (2020). These are at such a small scale feature that they do not affect play-scale exploration geology, and they do not give clues to the tectono-stratigraphic development of the region. The big mid-Oligocene sea-level fall has never been recognised (many references; just one from memory Saller et al., 1993 on detailed examination of the Oligocene Berai Limestone in outcrops and wells). The next biggest at 10 or 11 Ma has also failed to be found, although this statement would take more time to validate as many people claim to have found it. Lunt (2021b) examined one of these claims from Luconia and when strontium dating is corrected to the same time scale. If you have poor age control, all sorts of correlations can be imagined.

In closing, if you believe the Cenozoic eustatic curves of Haq et al. (1987) or Haq and Al-Qahtani (2005) (see this blog) you would expect a gradual sea-level decrease from mid Eocene times to now. Yet the basins of SE Asia invariably underwent subsidence and growth from mid Eocene to almost mid Miocene times with relative sea-level rise. The tectonism was overriding the eustatic signature.

References

Hutchison, C.S., 2005. Geology of North-West Borneo: Sarawak, Brunei, and Sabah. Elsevier Science.

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

Lunt, P., 2019b. The origin of the East Java Sea basins deduced from sequence stratigraphy. Marine and Petroleum Geology 105, 17-31

Lunt, P., 2019c. 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., 2021a. A reappraisal of the Cenozoic stratigraphy of the Malay and West Natuna Basins. Journal of Asian Earth Sciences: X 5, 100044

Lunt, P., 2021b. Tectono-stratigraphic framework of Luconia carbonates. SEPM Special publication, Cenozoic Isolated Carbonate Platforms – Focus Southeast Asia 

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

Lunt, P., Madon, M.B.H., 2017. A review of the Sarawak Cycles: History and modern application. Geological Society Malaysia Bulletin 63, 77-101

Madon, M.B.H., 1999. Geological setting of Sarawak. In L. K. Meng (Ed.), The Petroleum Geology and Resources of Malaysia, 273-290. Kuala Lumpur: Petronas.

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

Posamentier, H.W., Jervey, M.T., Vail, P.R., 1988. Eustatic controls on clastic deposition; I-conceptual framework. Sea-level changes; An integrated approach SEPM Special Publication 42, 109-124

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.

Vahrenkamp, V.C., 1998. Miocene carbonates of the Luconia province, offshore Sarawak: implications for regional geology and reservoir properties from strontium-isotope stratigraphy. Geological Society Malaysia Bulletin 42, 1-13