A plethora of new data has positioned the Carnian period of around, 237–228.45 million years ago as a period of significant climate and environmental change.
Geologists Uncover Global Evidence of Significant Climate Shifts During the Carnian Pluvial Episode
Geologists Schlager and Schollnberger investigated Austria’s Northern Limestone Alps and discovered a layer of dark grey siliciclastic rock, indicating very wet conditions within the era’s dry carbonate rock layer in the 1970s.
- The same layer was later uncovered by geologists in England, Israel, Italy and the U.S.A., solidifying the base for the occurrence of the Carnian Pluvial Episode.
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About Carnian Pluvial Episode
- The Carnian Period: The earth’s surface was still divided into the Pangea ( It was one massive supercontinent where, all the continents were joined together) and the Panthalassa (one vast ocean)
- The Pangea was surrounded by mountains and as a result, all its central area was under a long dry spell, and some rainfall was present only at its edges near the vast ocean.
- The Carnian Pluvial Episode: The middle Carnian (c. 232 Million years ago) experienced a brief interval of increased temperatures and multiple episodes of very heavy continuous rainfall, which is today called the Carnian Pluvial Episode.
Theory About the Causes
- Volcanic Eruptions: A series of very powerful volcanic eruptions took place in the Wrangellia Terrane, today’s Alaska and British Columbia, concentrating the atmosphere with massive amounts of carbon dioxide.
The massive amount of now released carbon dioxide in the atmosphere has contributed to the global warming phenomenon.
- Pressure gradient created: The emergence of a new mountain range, the Cimmerian orogen, created a strong pressure gradient between the ocean and the continent, creating a monsoon phenomenon deep within the Pangea.
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Effects of Carnian Pluvial Episode
- Raising Temperature: Due to the volcanic activity Earth’s temperature rose by 3-4 °C. The planet’s average temperature before CPE was already 10 °C higher than today
- Ocean Acidification: A change in the ocean’s salinity might also have taken place with the rise of CO2 in the atmosphere.
- Increased Fluvial Input: The beginning of the CPE is marked by a switch from shallow marine carbonate and evaporates to siliciclastic and dark organic rich sediments, likely resulting from increased fluvial input.
- Fluvial systems expansion: The spatial distribution of fluvial systems expanded and semi-permanent lakes were formed on land.
- Mass extinction: The CPE episode lead to mass extinction of species with several ammonite and conodont groups becoming extinct. Suspension feeders living in shallow marine habitats (e.g., crinoids: sea lilies) were also severely impacted by the high siliciclastic input and marine eutrophication.
- Emergence of Dinosaurs: The CPE was followed by the first appearance of the dinosaurs, marking the beginning of the “age of the dinosaurs.”
- Furthermore, the origination of many modern animal groups e.g., turtles, crocodiles, lizards and mammals occurred during the Carnian.
June 3, 2024
