The Meratus Mountains are composed groups of Ultramafic, Malihan, Melange and breakthrough rocks (Ofiolite series) which are estimated to be Yura (150–200) years ago until Early / Lower Cretaceous (100-150) million years ago.
The developing structural pattern in Borneo Island is in the Meratus direction (Northeast-Southwest). This pattern does not only occur in fault structures but also in the direction of the fold axis. The Tutupan Hills, which has a Northeast-Southwest direction with a length of about 20 km, has formed due to the movement of 2 (two) thrust faults that have same direction. One of them is known as the Dahai Thrust Fault which extends along the Western foot of the Tutupan Hills. In general, according to Van Bemmelen (1949), the physiography of Borneo Island is divided into several physiographic zones, namely:
The general Geological Conditions of South Kalimantan are divided into 3 (three), namely:
Meratus Mountains is a meso-tethys suture resulting from collision between Schwaner and Paternoster microcontinents in the Early Cretaceous period, in which its emplacement was done through the obduction process of detached oceanic slab which then rose to the surface due to the exhumation of Paternoster slab underneath (Satyana, 2003 -HAGI & IAGI; Satyana & Armandita, 2008-HAGI, Satyana, 2010-IPA; Satyana, 2012-AAPG). Exhumation is the re-lifting of a mass that once sank. Meratus Mountains Geopark has a relatively tectonic activities. It is based on two tectonic sutures assessed with metamorphic evolution performed by Soesilo et.al. (2015) and limited by Paternoster Microcontinent.
The South Kalimantan Mountains is an ophiolite mountain, in which since Paleogene has been located in an area far from the edges of the plate convergence zone. The Meratus Mountains began to rise in the Late Miocene and effectively confined the Barito Basin in the west during the Pliocene-Pleistocene epochs (Satyana). Based on the results of reconstruction carried out by Satyana (2003) on the tectonics of the Southeast part of Sundaland (Southeast Kalimantan, Central Java-East Java, South Sulawesi), it stated that the ophiolite of the Meratus Mountains should not be associated with the ophiolites found in Ciletuh and Luk Ulo (Karangsambung) as has been described by Katili (1974) and Hamilton (1979) who called it as the Late Cretaceous subduction pathway. The emplacement process of Meratus ophiolite is different from that of Ciletuh and Luk Ulo emplacement processes. Ophiolites in Ciletuh and Luk Ulo (Krangsambung) should be connected with outcrops of ophiolite complex in Bantimala, South Sulawesi, in which based on the age of metamorphism and radiolaria formed around the Maastrichtian (late Cretaceous), while the emplacement of Meratus ophiolite occurred during the Albian-Aptian (the upper part of Early Cretaceous).
The rocks found in Meratus Geopark are ophiolite series that had been exposed due to the obduction of Paternoster Microcontinent over the Sundaland in the Early Cretaceous (137–110 million years ago). During this period, the continental crust was located at the rear part (Southeast) of Paternoster Microcontinent, i.e. South Sulawesi Block which started to pierce downward of the microcontinent and the obduction process that began the occur up to the collision in the Late Cretaceous. So that the ophiolite series in Meratus and Karangsambung – Cileutuh had different age and period for Meratus Ophiolites were the products of subduction-obduction and collision of Paternoster Microcontinent over the Sundaland where in the end had caused the ophiolite series were exposed to the surface, whereas the ophiolites of Karangsambung–Ciletuh were the results of subduction-collision of South Sulawesi Block (Bantimala) over the Paternoster Microcontinent.
During the periods of tectonic activities found in South Kalimantan, in this case the formation of Meratus Mountains, there was found the building rocks of Meratus ophiolite series and sedimentary basin consisted of 8 (eight) process of geological periods, among others,
Period 1: Pre-Tertiary/Early Jurassic (190-165 million years ago)
Period 1 PreTertiary/Early Jurassic (190-165) mya illustration.
In this period, Paternoster Microcontinent started to move towards the Southeast direction and experienced the subduction process over the Sundaland that led to the volcanism process and the formation of Schwaner Mountains due to the molten of oceanic crust that pierced downward. During this period, it was the beginning of the mantle rocks formation in South Kalimantan in form of Metamorphic Rocks. The presence of these metamorphic rocks, such as Schist and Gneiss, were exposed very well in the Geosites of Matang Keladan and Gunung Belanda.
Sample and Petrography of Gneiss in Gunung Belanda
Period 2 : Late Jurassic – Early Cretaceous (165-137 million years ago)
Period 2 Late Jurassic – Early Cretaceous (165-137) mya illustration
In this period, the Paternosfer continental crust pierced down toward the Sundaland and both continental crusts had getting closer. It led to the pre-collision process towards Paternoster Microcontinent by South Sulawesi Blocks that resulted in the cessation of volcanism activities of Schwaner Mountains. The volcanism process that had formed the Schwaner Mountains began to stop. During this period, rocks in form of ophiolite sequences resulted from previously formed collision and metamorphic processes, were lifted and turned into the High. The formed ophiolote sequences could be found in various locations and constitute the relatively complete ophiolite series.
The rocks of Ophiolite series (mantle) are: Dunite, Peridotite and Pyroxenite
The rocks of Ophiolite Series: Gabbro
The rocks of Ophiolite Series: Pillow Basalt
The rocks of Ophiolite Series: Chert
Period 3: Early Cretaceous (137-110 million years ago)
Period 3 Early Cretaceous (137-110) mya illustration
In this period, Paternoster Microcontinent got closer to the Sundaland that led to the process of detached oceanic crust or slab break-off which cut off from the oceanic crust in front of the Paternoster Microcontinent and continued with the collision process which eventually formed the Meratus Ophiolite.
Along with the formation of Meratus Ophiolite, oceanic crust in front of the South Sulawesi Blocks kept on piercing down the Paternoster Microcontinent and caused the volcanism process in the Meratus High, it was proven by the discovery of volcanic and plutonic igneous rocks (Diorite Intrusion) that had acid and intermediate natures and belonged to the Group of Batanglai/Belawayan Granite. Some of locations that were exposed well, such as Kilat Api Waterfall, Balawaian Waterfall and hot springs (Tanuhi and Hantakan).
Sample and Petrography of Diorite in Kilat Api Waterfall
Sample and Petrography of Porfiri Granite in Kilat Api Waterfall
In addition to the discovery of ophiolite sequences, there was also a formation that had been the characteristic of this period of time, namely Batununggal Formation which formed due to the process of sedimentation in the areas with calm energy thus rich in carbonate elements.
The emergence of Batununggal Formation can be found in Bukit Langara and Bukit Kantawan in the Sub-district of Loksado, Hulu Sungai Selatan Regency.
Period 4: Late Cretaceous (100-71 million years ago)
Period 4: Late Cretaceous (100-71) mya illustration
In this period, along with the movement of oceanic crust in front of the South Sulawesi Blocks towards Paternoster, there was a more intense volcanism process. This volcanism process was proven by the presence of andesite lava and volcanic breccia which were predicted as the source of hot springs located in the area of Meratus Mountains. Also, it was proven in this period the forming of Haruyan Formation with its characteristic in form of rocks as a result of volcanic activities and the Pitap Formation with its characteristic of sediment deposits of flysch in the forearc basin. Haruyan Formation is found in various locations with different lithological units, such as in Lok Lagah, Barajang Waterfall, Gantungan Iwak Waterfall, and Haratai Waterfall. The phenomenon of hot springs also can be found in Lok Bahan Hot Spring and Batu Bini Hot Spring.
Period 5: Paleocene (71-56 million years ago).
In this period, subduction of South Sulawesi Blocks over the Paternoster Continent kept on moving and almost of the areas were lands thus experienced the processes of erosional and gliptogenesis.
Period 6: Eocene-Miocene (56-23 million years ago)
Period 6: Eocene-Miocene (56-23) mya illustration
Along with the reduced subduction intensities of Paternoster Microcontinent, there was an extensional rift that led to the formation of block faulting and became a vessel for the sedimentation of various formations. During this period, Barito and Asam Asam Basins were created. These basins were indicated as unity of depocenter during the Eocene which had a tendency of the same lithological characteristic unit. Rock formation belonged to this geosite was dominated by Tanjung Formation that had age of Middle Eocene-Early Oligocene (36.5-46 million years ago), Berai Formation that had age of Early Oligocene-Early Miocene (16-36.5 million years ago), and Dahor Formation that had age of Late Miocene-Pliocene (1.8-11.2 million years ago).
Tanjung Formation is characterized by the existence of conglomerate rocks, standstones, and coals in Tanjung Bawah, and limestones in Tanjung Atas. The limestones in Tanjung Atas are found having karst landscapes in several areas, where it is not only seen from eksokarst aspect but also from the endokarst aspect, such as the presence of cave interior which was still very natural and the underground water flows. This model also can be seen in the geosites of Air Kukup Cave, Berangin Cave, and Pasulingan Cave. The coals in Tanjung Bawah Formation can be ideally found in the rock exposure located in Sugai Taib Village, Pulau Laut Utara Subdistrict, Kotabaru Regency.
Air Kukup Cave (Upper) and Pasulingan Cave (Below) in Nateh Village as the Characteristic of Upper Tanjung Formation
Coals in Sugai Taib Village, Pulau Laut Utara Subdistrict, Kotabaru Regency as the Characteristic of Lower Tanjung Formation
Baramban Cave, Liang Akar Cave, and Liang Udud Cave as the Characteristics of Berai Formation
Aerial Photos of Lanscape Karst in the Area of Baramban Cave, Liang Bangkai Cave and Liang Udud Cave
Period 7: Plio-Plistocene (5-1 million years ago)
Period 7: Plio-Plistocene (5-1) mya illustration
In this period, there was relatively intense geological structure activities, marked by up and sliding faults, followed by down fault, thence formed a pathway for the source rock to inject the crude oil towards the rocks that had good reservoir characteristics, as well as a trap in the reservoir that had been formed. During this period. There was also the sedimentation of Dahor Formation that had characteristic lithological unit in form of clay up to loam stones, and sandstones. In Biru Lake location, there is a lithology as the characteristic of this formation, namely sandstones and clay.
Period 8: Recent (1 million years go – now)
In this period, there was a material sedimentation of loose sediment in form of alluvial deposits derived from the process of formation weathering of rocks that formed Meratus Mountains. Alluvial deposits found in Ujung Murung Village, Cempaka Subdistrict, Banjarbaru Regency, contain primary diamond estimated came from the sequence of ophiolite products, subduction result products, and exposed to the surface through kimberlite or lampropite pipes, or as the results of sedimentation of ancient river flows in the Schwaner and Gondwana Complex that had been still a unity in the Late Jurassic.