Explaining a new paradigm is proving to be difficult. Even though the old paradigm was broken, people continued with parts of it as suited their local requirements. That does not mean the old paradigm worked, only that the need for formation, sequence or surface names overweighed the need for a tested, predictive description of regional geology. Others concluded that things were just complicated and best viewed from a distance, as a simple form; an attitude that inevitably prevents analyses and advance. This “works” only if you want to stay in the same intellectual place, ignoring the occasional bust (like the anomalies of Maxwell’s equations and black body radiation bust early 20th century physics).
The new paradigm is a work in process and only parts of it are completed, and so a simple, short summary of an unfinished job is likely to appear incomplete and rickety. Definitely contentious, simply because it is change. Criticism of the old paradigm is something I have tried but it’s a very negative way of presenting a science. The critical approach can stimulate good debate (thank you very much to two local professors who have been absolute gentlemen in this field), but it can also divide opinion and lead to un-necessary polarisation.
It is perhaps safer to discuss the change in methods and philosophy that drives the paradigm shift. However there is a danger of falsely misrepresenting the old paradigm in a straw-man argument. So I am going to attempt a one-sided description of the new approach and the inevitable movement to new basin tectono-stratigraphy and play scale concepts. In part 2 and on this slightly older post I outline a little of what the new paradigm looks like.
I like using North Sumatra as an example because myself, Mobil field geologists, and Esso well analysts across the border in west Thailand, all independently saw the same basic stratigraphic ingredients. (See this link). Being the last worker on the scene I eventually found and could use the early worker’s observations. In mid Oligocene times a huge area (>50,000 sq. km) changed from being non-marine or locally inner neritic to be directly overlain by bathyal clays with occasional sandy turbidites. I invoke Walther’s Law to claim that such a rapid, step-like change could not be significantly diachronous, and was therefore a first-order sequence boundary under the definition of Posamentier et al. (1988). Then I highlighted the overlooked fact that these same Late Oligocene bathyal clays were directly below the reef of the Arun gas-condensate field, so another but more localised tectonic event close to the Oligo-Miocene boundary had uplifted this sub-region back to sea-level again. This reef terminated near the end of the Early Miocene and sank so deeply and quickly that thousands of metres of bathyal Middle Miocene to Recent clastics were deposited over the reef crest (with shallowing environments of deposition over the past 10 Ma; Lunt 2019).
As recently as early 2022 I was sent a paper to review (submitted by an international oil company to a Q1 journal), in which North Sumatra was a rift to sag back-arc basin. If you stand back from the data and do not observe facies, age, rate of change, thickness and a history of accommodation space, you can live with the old concepts, but you will be wrong. If you zoom-in and analyse the reliability of each data point it forces a new account of how a basin formed, and how the reservoir for a super-giant field was deposited and then sealed. We still do not know the source rock of this super-giant field, because our assumptions told us this was not necessary. We could just assume it from the old paradigm.
Once you begin to look, most basins in SE Asia have tectonic anomalies like those in North Sumatra, often just in a part of a “basin” or just at a certain period of its history, although often at several times at the same site. Sometimes these events correlate over wide areas indicating regional episodic tectonic activity, which is not expected by the old paradigm (which admittedly had very little predictive power). The very high rate of geological change during these times of transition is highlighted time and time again. We are not in a slow, ponderously changing tectonic setting overprinted by small but sudden eustatic events. Basins do not typically have a rift-sag history, of local rift expanding to a slower subsiding but more widespread post-rift sections, a style that is repeatedly cited in the old paradigm (cf. Doust and Noble, 2008; see this link).
Quantitative stratigraphic analysis leads to one assumption after another just dropping away. The basins become dynamic entities, and the facies (petroleum systems elements) have a wholly new palaeogeography. This is the work in progress. The changes are very surprising because we have lived with old concepts such as rift – sag, relatively static basin concepts for so long, as well as a plethora of formation and unconformities that are portrayed as being scattered almost randomly through space and time (like my pet-hates, the Ngimbang Formation of East Java, or the MMU of the South China Sea). Once you get to begin to ask “which MMU?” you are already halfway a convert to the new Paradigm. You have begun to walk towards and cross-examine the data. The MMU is not diachronous; that would break Walther’s Law (it is not a surface, it is a break between sedimentary systems, separated by a surface).
A new process of analytical stratigraphy forces new ranking of observations, in areas from North Sumatra, to East Java, Makassar Straits, Tarakan, Sabah, and Sarawak to East Natuna. The old paradigm ignored the fact that the Arun reef was deposited on only slightly older but bathyal clays, and the same type of massive uplift contact is present at NSA-1D and surrounding reefs in eastern Java (but in mid-Oligocene times, within NP24; Lunt, 2013- the exact same time as when the bottom dropped out of the N. Sumatra to W. Thailand area, and an unconformity across the South China Sea). Elsewhere coal-bearing coastal plain siliciclastics or inner neritic reefs are abruptly overlain by bathyal clays of considerable thickness and rapid rate of deposition. The old paradigm simply ignored these anomalies (non-Waltherian contacts), and de-valued them by ignoring the scalar properties of palaeobathymetry, geological speed and rates of sedimentation. Or did not notice simple mis-correlation. In the North Sumatra example I discuss how the “Black clays” (Zwarte Kleisteen) were called Bampo Formation, but the data shows there were two very different formations of different ages and tectono-stratigraphic settings.
There comes a time when a critical mass of such quantitatively described and validated “busts” demonstrates that these are not just local peculiarities, but indicators of a whole new pattern of basin development and sedimentation. I have written some pretty dull papers these past 5 years but they all contain detailed examination of such “busts”. Paradigm shift is inevitable. The only question is; have I and my co-workers interpreted the best new explanation of the tectono-stratigraphic data?
Very little of this is seen on seismic. Yes, retrodictively we can deduce an interpretation onto seismic once a tectono-stratigraphic framework is proposed, but the seismic data simply lacks accurate facies or age (& rate of change) data sufficient to propose, develop and test a new geological paradigm in an inductive fashion. In this matter seismic data follows, it cannot lead.
This is where we have been stuck for 20 years. Awed by the great improvement in seismic images but still just standing well-back looking at low resolution geological models and ignoring the very large number of “busts”. The exciting part is that we can use the same analytical methods that are used to build the new paradigm to extrapolate data into un-drilled areas, or slightly older histories.
References
Lunt, P., 2013. The sedimentary geology of Java. Jakarta: Indonesian Petroleum Association., 346
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
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