At first it seems not possible. How can the stays of sea creatures find yourself on mountaintops, tons of of kilometers from the closest shore? But across Southeast Asia – from Langkawi in Malaysia to the highlands of Brunei and Sumatra in Indonesia – scientists have discovered fossils of marine animals embedded in rocks high above sea level.
These discoveries reveal one in all Earth’s best geological histories. The mountains and islands of this region were once a part of the ocean floor. Over thousands and thousands of years, the slow collision of tectonic plates has lifted the traditional seafloor upwards, turning what was once underwater into mountain ranges. The fossils left behind – coral, shells, fish bones and microscopic traces – are the last whispers of the long-vanished seas that when covered this a part of the world.
As the ocean rose to the mountains
About 400–500 million years ago, most of Southeast Asia lay beneath warm, shallow seas. These waters were teeming with life – corals, crustaceans, trilobites and early types of fish. When these organisms died out, their stays settled to the seabed and have become trapped in layers of mud, sand and lime. Over thousands and thousands of years, these layers have hardened to form sedimentary rocks wealthy in fossils.
Outcrops in Sabah, Malaysia, showing tilted layers of ancient marine sediments where scientists have discovered trace fossils – evidence of deep-sea life that when thrived on the ocean floor before the rocks were uplifted into the mountains. Locations include the Inanam, Sepangar and Sulaman areas, with visible “up” directions marked by arrows indicating the unique orientation of the seabed.
Source:
Bulletin of the Geological Society of Malaysia, Volume 71, May 2021.
But the earth’s crust never stands still. The movement of tectonic plates – the slow drift and collision of the planet’s surface – pushed ocean rocks upwards. The seafloor folded, cracked and rose to form hills and mountains. In some places, corresponding to Borneo and Sumatra, parts of the old seabed are actually hundreds of meters above current ocean level. The fossils preserved there are direct evidence of this transformation.
Malaysia: Ancient Oceans in Langkawi and Sabah
Langkawi, known today for its beaches and limestone caves, is home to one of the vital vital fossil records in Malaysia. The Tenjong Dendang Formation, a rocky layer greater than 440 million years old, incorporates fossils of trilobites and brachiopods, small sea creatures that lived in ancient seas long before the age of dinosaurs. These fossils were discovered within the limestone that when formed the seafloor, indicating that Langkawi was submerged in a warm tropical ocean through the Late Ordovician period.
Far to the east, in Sabah, the story continues within the Crocker Mountains. The rocks listed here are a part of an ancient deep-sea basin. Fossil burrows and feeding trails present in these rocks reveal the activity of marine animals that lived on the ocean floor tens of thousands and thousands of years ago. Today, these deep-sea sediments have been uplifted to form the mountainous spine of northern Borneo.
Brunei: Fossil sharks from the Miocene sea
In Brunei, paleontologists examining rocks in northern Borneo have discovered fossils of sharks, rays and other fish species from about 10 million years ago, through the Miocene epoch. These fossils were present in layers of marine sediment which have since been tilted and raised above sea level by tectonic activity.
The discoveries paint an image of a time when Brunei’s hills were a part of a shallow, tropical sea teeming with marine life. Over time, because the land rose, the marine sediments hardened into rocks, retaining traces of the creatures that when swam there. Today, these fossils help scientists reconstruct ancient ecosystems and understand how rising and falling sea levels shaped the evolution of the island.
Indonesia: Tips from Sumatra, Java and Kalimantan
In Indonesia, marine fossils appear on several islands, often hidden amongst limestone hills or exposed in river valleys. In Sumatra, for instance, the Merangin Geopark in Jambi Province preserves a unprecedented mixture of marine fossils and ancient plant stays. The rocks tell the story of a time when Sumatra lay beneath a shallow sea before it was lifted up and folded into the land we see today.
The rocky riverbanks of Merangin Geopark in Jambi, Indonesia, where layers of ancient marine limestone preserve fossils of coral and other marine life dating back tons of of thousands and thousands of years. These rocks once formed a part of the shallow ocean floor before tectonic forces lifted them to their present-day heights.
Source:
blog.bookingtogo.com
Similar stories appear in Java and Kalimantan, where scientists report fossilized shells, coral and fish stays inside sedimentary rock formations. These discoveries show that much of Indonesia’s current landscape – now covered with forests and volcanoes – was once a part of an ancient seabed shaped by long, slow geological forces.
What do these fossils tell us?
Each fossil present in the mountains of Southeast Asia is an element of the region’s deep puzzle. They reveal where oceans once spread, how islands were formed, and the way the continents themselves moved. Trilobites from Langkawi, shark teeth from Brunei and coral fossils from Sumatra tell the identical story: the ocean was here long before us.
For scientists, these fossils are worthwhile clues that help reconstruct the history of our planet’s surface. For everyone else, they’re a reminder that the bottom beneath our feet is all the time changing. The mountains we walk on today were once coral reefs. The limestone cliffs towering above us were once an underwater world.
