## 2 Geological Setting and Study Area  
### Geology of Malaysia  
In this study, the formations discussed are scattered across Malaysia. As stated before, Malaysia is generally divided into two main regions, Peninsula Malaysia and East Malaysia. Peninsular Malaysia occupies a total land area of 130,268 km\({}^{2}\)[28]. It has a length of 750 km and a breadth of 330 km. It is also known to be elongated in a NNW-SSE direction [28; 29]. The Johor Strait and the Straits of Malacca separate Peninsular Malaysia from Singapore Island to its south and western Sumatra Island, respectively (Figure 1). Peninsular Malaysia is a vital part of the Eurasian Plate and it is located at Sunderland, the Southeastern Asian part [28; 29]. The Peninsula was formed in the Cenozoic era, and it is known to be tectonically steady, with only a few tectonic activities, like uplifts, movement of faults, tilting, and local gentle down warps [30]. Peninsular Malaysia is divided into three belts: the Eastern belt, the Western belt, and the Central belt. The division is based on the belts' different geological characteristics [31; 32; 33]. The Central and Eastern belts of Peninsula Malaysia are split up by the Bentong-Raub suture zone [31; 34; 35]. The Upper Paleozoic rocks can be seen in the three belts of the Peninsula, while the Lower Paleozoic rocks can only be seen in the Western part of the Peninsula [28]. The following studied rock formations/basins are all located in Peninsula Malaysia; Belata, Semanggol, Kroh, Semantan, Batu Arang, Batu Gajah and the Penyu. All the formations mentioned are in the Western belt of Peninsula Malaysia, except for the Penyu basin, which is in the Central belt (Figure 1). The ages of the formations studied range from the Silurian to the Tertiary periods (Figure 2). The geology of East Malaysia is divided into two main areas, the Sabah region, and the Sarawak region. Sarawak is subdivided into three tectonstratigraphic zones representing the decreasing stratigraphic and structural complexity towards the east [36; 37; 38]. The three zones are the Kuching, Sibu, and Miri zones [39; 40; 41]. The Kuching zone is located in the westernmost Sarawak, west of Batang Lupar [42]. The Kuching zone is thought to be a marginal part of the West Borneo basement, which spreads southwards into Kalimantan [36; 43]. The Sibu Zone is located in the center of Sarawak, and it is predomainely composed of thick shale-sandstone turbidite sequences accumulated in the oceanic crust [44; 45]. The Miri zone is the youngest of the three zones and it is located in the northeast [36]. The Tatau-Mersing line acts as a boundary between the Sibu and Miri zones. The following studied rock formations are all located in the Sarawak region: Bintulu, Belaga, Nyalau, Begrih, Liang, Balingian, Mukah, Lambir, Miri, and Tukau (Figure 1). The ages of the formations studied range from the Middle Cretaceous to Tertiary periods, with most of the formations found in the Miocene epoch (Figure 3a). Figure 1: Map of Malaysia showing the locations of the formations analyzed in this study. Sabah occupies an area of about 76,115 km\({}^{2}\) in the northern part of Borneo Island [46; 47; 48]. It lies next to actively moving plates in the southeast Asia region [49]. The area's topography is considered rough, particularly on the west coast. Sabah is mainly composed of thick, folded, Upper Cretaceous to Tertiary marine sedimentary rocks, lavas and plutonites, and subordinate Mesozoic metamorphic rocks [46; 50; 51]. Near the west coast is a distinct mountain range that includes the Palaeogene Crocker formation and other older rock units. It rises to between 3000 to 4000 m above sea level, culminating in the Late Neogene Kinabalu granodiorite intrusion, which peaks at 4101 m [49; 50; 51]. The following studied rock formations are all located in the Sabah region: Ganduman, Sebahat, Tanjong, Sandakan, Temburong, Pinangah, Beliat, Melian, West Crocker, Setap, Kapilit, and Kalabakan (Figure 1).