Chapter 6 Kalimantan

Summary

This presentation covers the geology of Kalimantan, Indonesia, highlighting key geological features such as sedimentary basins, tectonics, and sedimentation rates. It explores the region’s basement rocks, including volcanic, metamorphic, and granite formations, and their relationship to surrounding geological systems. The script delves into the significant delta systems, including the Mahakam, Tarakan, and Baram deltas, and the region’s high sediment yield. Additionally, it discusses the impact of rifting, transgression, and inversion events on sedimentation patterns, as well as the area's carbonates and fossil-rich deposits. The presentation provides an in-depth look at the geologic processes shaping Kalimantan’s landscape.

Takeaways

• 😀 The geological basement of Kalimantan consists of diverse rock formations, including Cretaceous to Eocene rocks, with significant areas of melange and granitic units.
• 😀 Major sedimentary basins in Kalimantan include the Mahakam, Tarakan, and Baram Deltas, which play a crucial role in the region's petroleum system.
• 😀 The Mahakam Delta has a high sedimentation rate, with an influx of approximately 62 million tons per year, leading to the formation of an ideal delta fan.
• 😀 The sedimentary deposits in East Kalimantan are particularly thick, with the Kutai Basin having the most significant volume of sediment in the region.
• 😀 Kalimantan's tectonic history involves counterclockwise rotation and rifting events that influenced its current geological structure.
• 😀 The region has experienced multiple phases of basin inversion, particularly during the Miocene period, affecting sedimentation and basin development.
• 😀 The primary sediment sources for Kalimantan’s basins include the erosion of Cretaceous granitic mountains and the influence of the Southeast Asian tin belt.
• 😀 Marine carbonate deposits, particularly in the Mangkaliat Peninsula, played an important role in the region's sedimentary environment, with fossils dating back to the Oligocene-Miocene period.
• 😀 Neogene sedimentation in Kalimantan saw a significant increase in sediment production, with large deltas like Kutai and Mahakam forming during this period.
• 😀 Paleomagnetic data suggests that Borneo (Kalimantan) has undergone a counterclockwise rotation, which has shaped its tectonic evolution.
• 😀 The geological development of Kalimantan is crucial for understanding the region's natural resource potential, particularly in terms of petroleum and coal deposits.

Q & A

What are the primary geological units of Kalimantan's basement?

The primary geological units of Kalimantan's basement include the Borneo Central Range (Cretaceous to Eocene deposits), the Sabah Ophiolitic Complex (northern Kalimantan), and metamorphic rocks associated with volcanic deposits. The Ketus granite and tonalite, which date back to the Silurian to Permian period, are also part of the basement geology.

How does the sedimentation rate in Mahakam Delta compare to other regions?

The sedimentation rate in the Mahakam Delta is notably high, with an influx of 62 million tons per year, which is significant compared to other regions in Kalimantan. This high sediment rate contributes to the development of large and ideal delta fan formations.

What is the significance of the rifting event in Kalimantan's geological history?

The rifting event in Kalimantan played a crucial role in the formation of the Makassar Strait. It influenced tectonic dynamics and contributed to the development of sedimentary basins, allowing for the accumulation of significant sediment deposits across the region.

What are the main sedimentary basins in Kalimantan, and what is their significance?

The main sedimentary basins in Kalimantan include the Kutai, Tarakan, and Mahakam basins. These basins are significant for their thick sedimentary deposits, high sediment yield, and potential for hydrocarbon exploration, particularly in the form of petroleum systems and coal deposits.

How do sedimentary deposits in Kalimantan vary in terms of thickness and distribution?

Sedimentary deposits in Kalimantan are generally thicker in Eastern Kalimantan, particularly in the Mahakam and Kutai regions. The Tarakan basin also has significant sedimentary deposits, but with differences in volume compared to the other basins.

What types of rock formations are prevalent in Kalimantan's geological structure?

Kalimantan’s geological structure is dominated by a variety of rock formations, including metamorphic rocks, granites, tonalites, and sedimentary formations. These include significant carbonate formations in regions such as Barito, Kutai, and Tarakan, as well as Delta front sandstones and marine deposits.

What does the paleomagnetic evidence suggest about Borneo’s tectonic history?

Paleomagnetic evidence suggests that Borneo has experienced counterclockwise rotation over geological time. This tectonic movement is a significant aspect of Borneo’s geodynamic history and influenced the region's current geological structure.

What are the primary sources of sediment in Kalimantan during the Eocene period?

During the Eocene period, the primary sources of sediment in Kalimantan were derived from the erosion of Cretaceous granitic mountains. This material was then transported and deposited in the sedimentary basins across the region.

What is the role of Neogen sedimentation in Kalimantan’s geological history?

Neogen sedimentation plays a major role in Kalimantan’s geological history, contributing significantly to the volume of sediment deposits. The Neogen period saw the development of key delta formations, such as those in the Kutai and Mahakam regions, and the beginning of major sediment accumulation.

How has the sedimentation in Kalimantan contributed to its petroleum system?

The sedimentation in Kalimantan, particularly during the Neogen and Tertiary periods, has been crucial in forming petroleum systems. The thick sedimentary deposits, including delta formations and marine carbonates, have created ideal environments for the accumulation of hydrocarbons and coal, which are valuable resources in the region.