Before the islands rose, the Tunlob Schist already had a story to tell.
Deep beneath Cebu’s bustling cities and rolling hills lies a geological treasure. The Tunlob Schist is a rock formation dating back to the Jurassic period (approximately 201-145 million years ago). The discovery of this ancient metamorphic rock offers a glimpse into the Philippines’ prehistoric origins, revealing clues about the region’s tectonic evolution. Found within the Pandan Formation, this rock is a key piece in understanding how the Philippine archipelago formed through the collision of the ancient oceanic plates.
Plates First Danced
The Tunlob Schist is part of the Pandan Formation, a late Cretaceous geological unit in Cebu, composed of metamorphic and sedimentary rocks. Schist is a medium-grade metamorphic rock, meaning it was transformed under intense heat and pressure underground within the Earth’s crust. This discovery suggests that the Island was once part of a dynamic tectonic boundary, where plates collided and subducted millions of years ago. Studies indicate that the Tunlob Schist contains minerals and geochemical signatures associated with the Australian continental margin. It means that Cebu’s rocks may have originated from ancient fragments of the Australian crust. Making the Schist a crucial piece of evidence in reconstructing the Philippines’ geological history.
Under Press
The fascinating metamorphic rock, Tunlob Schist, is formed under the intense pressure likely due to subduction, where tectonic plates slide beneath one another. Composed of minerals such as chlorite, muscovite, and quartz, its composition suggests it originated from deep-sea sediments or volcanic rocks that underwent significant transformation over millions of years. The surrounding Pandan Formation dates back to the Late Cretaceous period. The rock itself may be older, possibly dating back to the Jurassic era, based on geological comparisons with similar rock formations in the region. The Tunlob Schist is exposed in areas where erosion has stripped away the younger layer of rocks, revealing the hidden relics of the Earth’s dynamic past.
Proof Written In Stones
The discovery of Tunlob Schist serves as a geological time capsule, offering invaluable insights into the Philippines’ history. The presence of the rock helps scientists trace the origin of the archipelago’s tectonic origin, revealing connections to the continent of Australia and an ancient ocean basin. Moreover, studying this rock enhances our understanding of how our island is shaped based on subduction and the mountain-building process. For geologists and rock enthusiasts alike, the Tunlob Schist is a rare and tangible link to the Jurassic era, making it a remarkable discovery and a national treasure here in Cebu.
As research continues, the Tunlob Schist stands as a witness to Cebu’s ancient past, from a time when dinosaurs still roamed the Philippine island as it was still forming. The Jurassic-age rock may reveal valuable information and secrets about the force that formed our majestic Island as we know it today. For those who seek to uncover the mysteries beneath our feet, Cebu’s geological wonders offer a fascinating journey through deep time.
