Virtual Vlog Fieldtrip Northeast Java Basin - Stopsite 1

Summary

This field trip takes participants along the northern coast of Java, exploring the geological and ecological transitions in the region. From studying coastal processes like salt pond evaporation and shrimp farming to examining tectonic forces shaping the North East Java basin, the trip covers a range of topics. Participants learn about mangrove ecosystems, coral reef development, and sedimentation patterns, applying geological principles like uniformitarianism. The focus shifts from present-day coastal features to understanding the region's deep geological history, offering insights into volcanic arcs, back-arc basins, and tectonic evolution.

Takeaways

• 😀 The location being discussed is Red Bridge Beach, part of the North East Java basin, where coastal processes will be observed and linked to rock sequences.
• 😀 The area is known for the interaction between different geographical features, including mangrove forests, shrimp ponds, salt ponds, and volcanic formations.
• 😀 Marine fisheries, especially fennema shrimp ponds, face challenges due to high tides that can damage the embankments of the ponds.
• 😀 Salt ponds in the area undergo a gradual evaporation process, starting with the formation of aragonite crystals, followed by gypsum, and finally NaCl salt.
• 😀 The artificial mangrove forest plays a crucial role in protecting both shrimp and salt ponds from coastal erosion and saltwater conditions.
• 😀 The geological history of the region is linked to tectonic activity, with the North East Java basin influenced by subduction and volcanic processes along the Sunda arc.
• 😀 The evolution of the region includes the transition from a deep sea environment to shallow seas, followed by uplift processes during the late tertiary period.
• 😀 The North East Java basin’s unique tectonic pattern does not follow the typical back-arc basin model but is controlled by older tectonic structures.
• 😀 The geological stratigraphy of the area, especially along the North coast of Java, shows a complex interaction between volcanic arcs, sedimentation, and tectonics.
• 😀 The study of coastal processes, including tidal flats, mangroves, and coral reefs, provides insights into the historical and current sedimentary environments, demonstrating principles like Wolter's law and uniformitarianism.

Q & A

What is the significance of the Rembang beach mangrove forest?

The Rembang beach mangrove forest is a crucial area for understanding the transition between the North East Java basin offshore and the coast. It also plays a key role in protecting the local shrimp and salt ponds from high tides and erosion.

How does the process of salt formation occur in salt ponds?

The process of salt formation in salt ponds occurs gradually through evaporation of sea water. Initially, elements like aragonite or calcite (CaCO3) form, followed by gypsum (CaSO4·H2O), and finally, NaCl (salt) forms as the water evaporates and the volume decreases to 10%.

What is the role of mangrove planting in the area?

Mangrove planting in this area is artificial and serves to protect the local shrimp and salt ponds, reducing the risk of damage from high tides and saltwater intrusion. The mangroves also contribute to maintaining ecological balance and protecting the coastline.

What tectonic forces influence the North East Java basin?

The North East Java basin is influenced by tectonic forces, including tension forces that affect the evolution of the basin. These forces are responsible for the basin's formation and sedimentation processes, particularly the subduction of the Indo-Australian plate beneath the Sunda Shelf.

How does the geological structure of Java affect its current volcanic activity?

The geological structure of Java is shaped by the Sunda arc, where the subduction of the Indian Ocean crust beneath the continental crust of the Sunda Shelf generates magma, leading to volcanic activity. The North East Java basin is located within this active volcanic arc.

What is Wolter's Law and how does it relate to stratigraphy?

Wolter's Law states that sedimentary layers deposited side by side in a modern environment will also be found vertically in the stratigraphic record. This law helps to interpret the vertical relationships between clay, sand, and carbonate layers based on changing sea levels.

How do changes in sea level affect sediment deposition?

When sea levels rise (transgression), sand deposits move toward the shore, and carbonate layers are pushed closer to the beach. Conversely, during a regression (falling sea levels), sand is deposited on top of carbonate layers, and clay layers move seaward.

Why are coral reefs able to develop along the north coast of Java?

Coral reefs are able to develop along the north coast of Java due to the lack of active volcanic activity in the area, allowing clear waters that support the growth of coral. Additionally, the coastline's morphology creates a favorable environment for coral reefs to thrive.

What are the primary differences between the North East Java basin and the ideal back-arc basin?

Unlike the ideal back-arc basin, which is typically oriented east-west, the North East Java basin develops northeast-southwest. This unique orientation is influenced by older tectonic structures that control the basin's evolution.

What is the significance of the Rembang anticlinorium in the geological study of Java?

The Rembang anticlinorium is significant as it represents a geological feature where hills run east-west, dominated by faults and folds. It is an important area for understanding the tectonic and sedimentary history of the region, particularly in relation to the North East Java basin's evolution.