Physiology and Morphology

As an archipelago, the Raja Ampat area consists of hundreds of islands. The main islands in the Geopark area are Waigeo, Batanta, Salawati, and Misool. The height of these islands ranges from 0 m to 920 m asl. Waigeo is the highest island, where the peaks of the mountains reach a height of 920 m asl. Misool Island, which occupies the southern part of Raja Ampat, has a maximum height of 327 m asl. The high peaks (Mount Kupel, Mount Zadel) and the surrounding area (Mount Zaag) are occupied by karstified limestone.

Mayalibit Bay in Waigeo becomes a striking landscape when the long bay that stretches in a northwest-southeast direction seems to separate the island into 2 parts. By genesis, small islands in the interior of the bay are sea-stacks whose formation is influenced by geological structures (faults). This landscape segment is part of the Mayalibit Bay protected area. Gam Island and Kabui Bay in the south-west of Waigeo are islands and a group of small islands that show a karst landscape. The sea waters that separate each island have a depth of between 20 m (on the outskirts of the island) and 200 m (in open waters).

The northernmost part of Raja Ampat Regency is occupied by the Wayag Islands. To the northwest and northeast are Pulau Sayang and the Pacific Ocean, respectively, where the Federal Republic of Palau is located. The waters west of Wayag are included in the area of Central Halmahera Regency, North Maluku Province. The sea depth outside the Wayag Islands is on average less than 100 m.

The Wayag Archipelago (including Pulau Sayang) which is the outermost archipelago of Indonesia is a group of islands with a distinctive morphology. This northern group of islands (Wayag-Quoy-Uranie) has an archipelagic karst landscape. There are more than 100 limestone islands in this area, with varying sizes. Quoy Island east of Wayag Island is also often called Yin Island; while Uranie Island, east of Bag Island by the locals is called Mace Island. The islands that stick out from the seabed have a maximum height of 75 m above sea level, with steep edges

The Wayag-Quoy-Uranie archipelago forms a line with a northwest-southeast trend. This lineament is controlled by a northwest-southeast fault, which appears to be the main geological structure at Waigeo. Estuaries or steep walls on hills are also caused by geological structures, namely joints and faults. Shallow sea waters (less than 20 m) on Wayag Island are lined with limestone islands with towers forming a kind of lagoon. The bottom of the lagoon is overgrown with coral.

The various types of limestone hills on Wayag Island, ranging in shape from sinusoids to cones (conical), with a flat surface similar to a plateau, to towers characterize the outer karst phenomenon in this area. The diversity of hill forms is influenced mainly by geological structures, both fractures (joints) and faults (faults).

From the lithological point of view, thick marl limestone which is softer and less resistant to dissolution tends to form a hemispherical hill with a curved peak. Limestone sequences, according to stratigraphy, are composed by alternating between easily soluble limestones and limestones that are more resistant to dissolution (coral limestones) which when karstified tend to form cones.

A hill or embankment with a flat top so that it gives a plateau-like appearance can be ascertained that the top is composed of limestone which is relatively soluble in type, such as marl limestone. The thick insertion of marl at the top of the hill also often triggers the formation of a hill with a horizontal peak. The rim of the plateau's hilltop is usually curved due to strong erosion and dissolution. The hillside with low horizontal peaks, which is on the beach and gives a terraced appearance, is interpreted as a step-beach landscape.

The faults and joints in the Wayag area are responsible for the origin of the various hills. Each protrusion is bounded by a vertical or nearly vertical wall, which is actually a fault plane or joint. The spread of the tower hills is so dense that there is almost no plain in between.

At Batanta, the rugged hills along the north coast have gentle slopes in the north and steep slopes in the south. Verstappen (1960) interpreted the rock formations as rock formations which in their development experienced a decline so that they were covered by the sea. The hills in central and western Batanta show karst topography. Dolina, uvala and polje color the limestone surface landscape, including several caves. The flow pattern in this karst segment tends to be below the ground surface.

Morphologically, Misool Island, which is located in the southernmost part of the Raja Ampat Regency, is divided into 3 geomorphological units, namely:

1. First, the lowlands that only develop in the northeastern part of the island. Its height ranges from 0-75 m asl. This landscape is formed by fine clastic sediments.
2. Second, the karst hills that develop in the middle. Its height ranges from 50-480 m asl. The topographical elements of the karst are dolina, caves and underground rivers. The lithology that forms it, namely limestone, is covered by Tertiary limestone or 52 million-30 million years old.
3. The three hills, spread out in the southern part of the island and form a narrow bund that surrounds the island in the north. The rocks are sedimentary rocks and low grade metamorphic rocks, which are exposed at an altitude between 100 m and 565 m asl. The main rivers on the island are the Fageo, Biga and Gam which have a branching pattern.

Uplifted coral reefs that form the shoreline were observed in the south-eastern part of Wayag Island. A similar phenomenon was seen on the islands of Mainsfield, Boo, Fam, Kofiau and Doif to the west of Batanta Island and Salawati Island.

Stratigraphy

Geopark areas reveal various types and ages of rocks, each of which is grouped into rock formations. Starting to become rocks and tectonic influences tell the geological history that began hundreds of millions of years ago until now.

Paleozoic Rock

These pre-Triassic rocks, or about 439 million-360 million years ago, were only exposed locally in the southwest part of Misool. This metamorphic rock unit that underlies the Mesozoic rocks is the oldest rock in the Raja Ampat Geopark area. Its thickness is thought to be more than 1,000 m (Rusmana et al, 1989).

Mesozoic Rock

This collection of rocks formed between 245 million and 65 million years was exposed at Waigeo, East Batanta, North Salawati and South Misool. In Waigeo the lithology is in the form of ultramafic rocks that are 148 million years old, and sedimentary rocks (Tanjungbomas Formation). In Batanta and Salawati there are sedimentary rocks and low grade metamorphic rocks (Waiyaar Formation, Tamrau Formation, Ofiolite Gag). While in Misool it is in the form of sedimentary rocks (Keskain Formation, Bogal Limestone and Napal Lios Members, Yefbi Shale, Demu Formation, Lelinta Shale, Facet Limestone, Fafanlap Formation). The thickness of all Mesozoic rocks is not less than 1,000 m.

Tertiary Rock

The Tertiary rock group in Raja Ampat which was formed between 66.5 million to 2 million years ago is mainly in the form of sedimentary rock, limestone, and volcanic rock. In Waigeo, there are Lamlam Formation, Rumai Formation and Volcano Rock Members, Yeben Formation, and Puri Formation.

In Batanta and Salawati there are Faumai limestones, Sirga Formation, Batanta volcanic rocks, Kais limestones, Klasafet limestones, Dore volcanic rocks, Sagewin limestones, Yaripi Formation, Marchesa Formation, and Klasaman Formation. In North Salawati, the Neogene age 11-2 million years old were found locally, including the Yefman Breccia, which was initially influenced by the Sorong Fault system which trended west-southwest-east-northeast.

Meanwhile in Misool, limestone is mostly karstified (Daram sandstone, Zaag limestone, Napal Kasim, Openta limestone, and Atkari limestone). Tertiary rock thickness reaches thousands of meters.