This essay was hard to figure out because of all the scientific terms involved. I have changed those terms to regular English so everyone can read it. I have also extracted those portions that relate to Borneo. We begin with portions of Pangea, the continent where every land mass was connected together, and then broke up into Gondowana and Laurasia.
A History of Plants, Trees and Borneo
Summary
The trees on Borneo, at the beginning probably were pine trees and conifers which came from Laurasia and broke off from the supercontinent Gondwana. ~215-175 million years ago
Borneo was in the northern hemisphere and rotated south towards the equator counterclockwise to its present position. With this rotation, the climate of Borneo warmed. North Hemisphere ~45-40 million years ago; rotation began ~34-23 million years ago.
Meanwhile, India broke off of Gondwana below the equator(130-120 million years ago) and was moving north and had collected plants from Africa. Some of these plants migrated over to Borneo. ~70-55 million years ago
India was moving north and Borneo was rotating south. They “passed” each other 45-30 million years ago
*India crashed into Tibet ~55-50 million years ago.
The Dipterocarps ( the jungle trees) migrated into Southeast Asia about 50-40 million years ago and then to Borneo. 34-20 million years ago
* Because of the way India was shaped it crashed into Asia before it passed Borneo.
Long Version
The crashing of the Indian plate into Asia occurred during the Eocene (56-34 million years ago). This event created an opportunity for the exchange of plants. India had already obtained plants from Africa during its northward journey.
During the Paleocene (66 to 56 million years ago) and early Eocene(56-34 million years ago), the plants of Southeast Asia did not have many species. Many were thought to come from the continent of Laurasia which broke off from the early supercontinent of Gondwana near the Sunda Shelf. The species were thought to be one or two species of palm trees.
This is indicated by spores and pollen found in old sediments drilled from the bottom of the sea in West Sarawak and the east Java Sea.
Some of the early flowering plants that lost their leaves in the cold were sandalwood and members of the elm family. There were also other pollen fossils recorded. Upland areas in Borneo probably housed plants from Laurasia.
The Kayan Alluvial Fan is off of East Borneo. It is a large formation of river sediment which flows into the sea and comes from the Schwaner Mountains, which form the backbone of Borneo. It dates to the Cretaceous Period(145-66 million years ago). This sediment housed pollen grains with two air sacs which allowed for wind pollination and is found in conifers and pine trees. Therefore, the Schwaner Mountains had pine trees and conifers 145-66 million years ago.
Following this period, there was the coal formation time period. Here thorny palms dominated in a very hot and humid environment. The Santonian era (86 to 83 million years ago) was noted for its high global seas, warm greenhouse climate and shallow seas that overlaid land areas. The pollen of these areas was found in Sarawak.
The Pedawn Formation is a geological formation located in the Kuching area. It lasted from the Jurassic(201 million years ago) to the early Cretaceous period. (145-66 million years ago). This formation showed very little diversity in plant life. The older period saw pine trees with small amounts of flowering plant pollen. Southeast Asia was a backwater for the expansion of flowering plants compared to Africa. It cannot be in any way the cradle for early flowering plants.
As India drifted towards Asia but before there was direct land contact and Southeast Asia and India had the same hot humid conditions, plants were able to disperse from India to Southeast Asia. Dispersals to Southeast Asia occurred in two stages: the first was lowland vegetation which included fossil pollen possibly from a flowering plant, elms, and the sandalwoods. The second was where beauprea, rain forest tree, iron and boxwood, pagar anak (used as a source of red dye in Sarawak), ramin( a hardwood found in peat forests) and kayu jati bukit(teak wood) were found in the hot and humid climate.
Shorea or the Dipterocarps in the middle of the Eocene (56-34 million years ago) show some pollen but were extremely rare. The dipterocarp probably arrived after India had smashed into Asia in the late Eocene(56-34 million years ago).
By the late Eocene or 41 million years ago there was a biogeographic connection between India and Southeast Asia. The Paleotropical Kingdom was formed which connected Africa, India and Southeast Asia with plant life.
Borneo
Several different models explain the tectonic history of Borneo. However, the Paleoclimate perspective places Borneo at very different latitudes during the Oligocene(33-23 million years ago) and Eocene. (56-34 million years ago) This means Borneo was rotating in an anti-clockwise direction since the Eocene. There are several models that dispute this scenario, some showing Borneo moving in a clockwise fashion.
The “best fit” hypothesis places Borneo in a northerly position in relation to the equator. This means that Borneo was located north of the equator. It then rotated counterclockwise downward to where the equator now passes through Borneo. This compliments the vegetation which was seasonal and finally tropical in nature.
The age of the tropical rain forest has been placed at ~48 million years ago. The diverse dipterocarps began at the beginning of the Miocene. (23-5 million years ago).
From
Morley, Robert J. The Establishment of Paleotropical Rainforests from Africa to Oceania in Relation to Plate Tectonics and Zonal Tropical Climates in London: Dupont-Nivet G. et al Asian Geodynamics, Climate and Biodiversity Geological Society special publication #549, 2025
I have a copy, just email me at Sa********@***il.com
Tom McLaughlin for BorneoHistory.com