A review of the Sarawak Cycles: History and modern application

Abstract

This review examines the history of the Sarawak "Cycles" and their application in subdividing offshore Cenozoic stratigraphy. The Cycles are widely but inconsistently used, at least in part because important reports and data collections were never published (e.g. Geiger, 1964;Hageman et al., 1987; Hageman maps, 1985, eventually reproduced in Madon, 1999and Hutchison, 2005and Taylor et al., 1997) or were published in highly abridged summaries only (Ho Kiam Fui, 1978;Mansor et al., 1999). The lack of a data-audit trail left open possibilities for ambiguity and confusion, as has been commented on by several workers (e.g. Snedden et al., 1995;Ismail & Tucker, 1999). This account reviews the major contributions, published and unpublished, and the concepts of the Cycles, especially over times of geological change. The data behind the model is cited in order to give confidence when integrating Sarawak stratigraphic data into a regional geological model. The Cycles began with an assumption that transgressions over regressive surfaces were distinct and approximately synchronous events for correlation. By including biostratigraphic data these transgressive events could be traced into clay-dominated areas, where lithological and seismic contrast was weak. This integrated approach was carried out through the 1970's and 80's, during which time the data pushed the model towards a three dimensional view of sedimentation, with the basin shape evolving and changing through time. However, development of a full tectono-stratigraphic model paused during the period of accelerated seismic capabilities of the 1990's and early 21 st Century. While geophysical data coverage increased, application of geological analyses decreased, and the integrated approach lost momentum. This review aims to re-establish the role of the Cycles as a part of a large scale geological model. An initial integration with regional geological events is attempted, linking some of the Cycle boundaries with times of known tectonic change. 78beyond the main Neogene clinoform, in deep water, with no Luconia reefs. Finally, onshore there was uplift where an older Miocene trend has been over-printed by a later Miocene uplift that is parallel to the present day coastline. In the coastal and nearshore areas there is strong reverse faulting, so this southern area, with its own distinct geological history, is called the Tinjar province.The challenge was how to correlate, and predict facies into un-drilled areas, in this broad region of sedimentation, with its gradual trend from coastal plain sediments in the south to open marine environments in the north, and how to correlate from clastic to carbonate facies in order to combine their sedimentological histories HISTORY OF STUDIESThe tools required to identify different facies in Sarawak sediments were developed early on, but the ability to correlate and thereby map facies variation at a specific time has always been challenging. Age diagnostic fossils occurred only rarely and consequently indicated only a general age, and ...

A new upper Paleogene to Neogene stratigraphy for Sarawak and Labuan in northwestern Borneo: Paleogeography of the eastern Sundaland margin

“…Cycle III is usually a thin unit in the Sarawak Basin and the top to Cycle IV is marked by carbonate growth in the Dangerous Grounds area (Wilson et al, 2013) which was interpreted as the main event in the Middle Miocene at c. 15-16 Ma, termed MMU (e.g. Doust, 1981;Lunt and Madon, 2017a). This age is similar to the previously reported age of the DRU and therefore some authors consider the MMU to be the same as the DRU (e.g.…”

Onshore to offshore correlation of northern Borneo; a regional perspective

“…This mid Middle Miocene event is close to the age of the Cycle IV to V subsidence in Sarawak (Lunt & Madon, 2017). It is also approximately the age of a sharp decline in activity of the Sulu volcanic arc (Figure 12), which may be linked to locally increased subsidence along that trend.…”

“…Although there had been hinterland uplift in central Borneo (described above), the first uplift along the elongate Western Cordillera to Palawan Island trend of the Sabah Orogeny is argued to have been in latest Early Miocene times. Note that this is at about the same time as the Sarawak Cycle III to IV boundary and the rapid rifting extension of the Bunguran Trough in west Sarawak at c. 16 Ma (Lunt & Madon, 2017).…”

“…In order to create accommodation space for such overburden to have been deposited these delta-top sediments must first have been subject to substantial subsidence. The mid Middle Miocene event, which was the termination of Tabin Limestone to the east and also top Cycle IV subsidence in Sarawak to the west (Lunt & Madon, 2017) is the most likely candidate for this, as it has the required magnitude. It was also followed by rapid sedimentation of the Sebahat and Ganduman formations as candidate overburden units, before a period of young Neogene uplift and erosion.…”

Seismic stratigraphy and sedimentology of a Miocene carbonate platform in Luconia, South China Sea

“…In the Central Luconia Province, Cenozoic sediment supply largely consists of coastal and marine clastic deposits (Doust, 1981). Previous studies (e.g., Ho, 1978) subdivided the Late Eocene to Pleistocene basin fill into a succession of eight seismic‐stratigraphic sequences from the interpretation of transgressive–regressive cycles in the Sarawak Basin (Lunt & Madon, 2017). The name ‘Cycle’ is here used to describe fining up/coarsening lithofacies stacks, separated by unconformities (Ho, 1978).…”