Permian, Triassic and Jurassic-aged Forests Explored on the Coldest Continent

Over the next few months, a team of intrepid scientists will be hoping to continue their exploration of some of the most remote fossil locations in the world.  Researchers from the University of Wisconsin-Milwaukee have been mapping the sedimentary deposits at McIntyre Promontory, at the head of the Ramsey Glacier in Antarctica.  To date, the team have recorded an extensive series of strata ranging in ages from the Late Permian to the Jurassic, the numerous plant fossils found are helping the scientists to better understand the evolution of forests and their flora over the southernmost portions of Gondwana.

Remains of Prehistoric Forests Uncovered in Antarctica

Prehistoric tree trunk (geology hammer provides scale).

An ancient tree trunk discovered in Antarctica.

Picture Credit: University of Wisconsin-Milwaukee

Antarctica in the Late Permian Period

A total of thirteen trees have been found with numerous fragmentary fossils of other plants, including Ginkgos and Glossopteris.  The oldest plants described by this research team, date from the Late Permian of around 260 million years ago.  Some of the fossils have stems and roots attached and have been preserved “in situ”.  No transport of fossil material is involved, the fossils are preserved where the plants grew.  The flora of this southerly habitat has been preserved thanks to occasional volcanic events that buried the primitive forests in ash.

Commenting on the significance of the Antarctic ancient flora, palaeoecologist and visiting assistant professor at the University of Wisconsin-Milwaukee Department of Geosciences, Erik Gulbranson stated:

“People have known about the fossils in Antarctica since the 1910-12 Robert Falcon Scott expedition.  However, most of Antarctica is still unexplored.  Sometimes, you might be the first person to ever climb a particular mountain.”

Beautifully Preserved Plant Fossils

Ancient plant fossils from Antarctica.

Ancient plant fossil remains.

Picture Credit: University of Wisconsin-Milwaukee

The Late Permian forests preceded the most extensive mass extinction event in the Phanerozoic (end Permian mass extinction event),  the scientists are hoping to use their growing knowledge of the ancient Antarctic forests to look at the possible impact on global warming on extant plant communities.  In addition, as the Antarctic forests grew at polar latitudes where plants can’t grow today, Gulbranson believes that the trees were an extremely hardy species and he and his colleagues are trying to determine why they died out.

Just like their modern counterparts, prehistoric tree fossils can reveal seasonal growth rings.  These rings when examined in microscopic detail can reveal patterns of seasonal growth.  Antarctica during the Late Permian was further north than it is today, even so, despite the milder climate, the forests would have had to endure prolonged periods of darkness, when the sun never emerged above the horizon.  The research team hopes to use the ancient growth rings to learn more about how these forests coped with such extremes.

Ancient Tree Trunks Can Help Decipher Seasonal Growth Patterns

Antarctic prehistoric plant life.

Ancient trees can reveal evidence of seasonal growth.

Picture Credit: University of Wisconsin-Milwaukee

Climate Change and the End Permian Mass Extinction Event

The cause or causes of the end Permian extinction event remain an area of controversy within palaeontology, although many scientists now believe that a huge increase in atmospheric greenhouse gases such as methane and CO2 which resulted from extensive global volcanic activity led to world-wide climate change.  John Isbell (University of Wisconsin-Milwaukee), has visited Antarctica before, on this expedition he examined the matrix and other sediments surrounding the in situ fossils to determine how these plant remains fitted into the geology of Antarctica.

To read an article written by Everything Dinosaur in 2015, that explains how rocks from South Africa are helping scientists to unravel global extinction events: Karoo Rocks Provide a Fresh Insight into Extinction Events

The Plant Fossils Might Represent New Species

The prehistoric forests of Antarctica.

Delicate plant fronds have been preserved.

Picture Credit: University of Wisconsin-Milwaukee

The extensive forests may have stretched across the whole of the super-continent Gondwana.  Evidence of Glossopteris fossils and other plant remains have been used to help substantiate the theory of continental drift.  These Permian forests would have looked very different from today’s temperate woodlands, the flora would have been dominated by mosses, ferns, Pteridosperms (seed ferns) and conifers.

Erik Gulbranson explained that the Antarctic fossils have provided important information about plant diversity at higher latitudes. During the Permian, forests were a potentially low diversity assemblage of different plant types with specific functions that affected how the entire forest responded to environmental change.  This is in direct contrast to today’s high-latitude forests that display greater plant diversity.

Gulbranson added:

“This plant group must have been capable of surviving and thriving in a variety of environments.  It’s extremely rare, even today, for a group to appear across nearly an entire hemisphere of the globe.”

Tough Forests Failed to Survive Climate Change

The researchers conclude that these tough trees and plants did not survive the climate change that marked the end of the Permian.  Younger plant fossils from Triassic and Jurassic sediments provide evidence of the changing Antarctic flora over time, but many of the types of plants found in the Permian forests, despite their resilience, died out.

Erik Gulbranson Can Study the Permian Plant Fossils in the University Laboratory

Plant fossils being examined.

Examining the Permian plant fossils (Erik Gulbranson – University of Wisconsin-Milwaukee).

Picture Credit: University of Wisconsin-Milwaukee/Troye Fox

By analysing the preserved tree growth rings, the scientists have found that these trees transitioned from summer activity to winter dormancy very rapidly, perhaps within a few weeks.  Extant plants make the same transition over the course of several months and also conserve water by making food during the day and resting at night.  Scientists don’t yet know how months of perpetual light would have affected the plants’ day-and-night cycles.

The team hope to return to the various Antarctic dig sites in the early part of 2018.  They hope to learn more about the annual growth cycles of the trees and to determine how the forests coped with rising levels of greenhouse gases and a warming climate.  It is hoped that by studying the Permian flora of Antarctica, models looking at how living plants will cope with climate change can be developed.

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