Paleogene
A 50 cm thick layer of rusty colored clay marks the start of the Paleogene period. This thin band sits at Oued Djerfane in Tunisia and contains an iridium anomaly from a massive asteroid impact. The clay was deposited over just a few days around 66 million years ago. Scientists call this boundary the Global Boundary Stratotype Section and Point for the Cenozoic Era. It separates the Cretaceous Period from the Paleocene Epoch, which lasted until 56 million years ago. Similar layers appear worldwide, containing microtektites and shocked quartz that confirm the extraterrestrial collision. The crater itself lies buried under the Yucatan Peninsula in Mexico.
Africa collided with Eurasia to form the Alpine-Himalayan mountain chains during the early Paleocene. This convergence created arcuate ranges stretching from the Tell-Rif-Betic cordillera to the Taurides. Subduction zones developed along the western Mediterranean where the European plate moved beneath Africa. By 40 million years ago, subduction began along the western Mediterranean arc of the Tell, Rif, Betic and Apennine mountain chains. The Zagros Mountains formed as the Arabian plate converged with Eurasia, creating a belt extending 2000 km across Iraq and Iran. India drifted northward at roughly 18 cm per year before colliding with Tibet around 55 million years ago. This collision produced the Himalayas through the scraping of metasedimentary rocks off the Indian continental crust.
The North Atlantic Igneous Province stretches across Greenland and northwest Europe margins. Two main phases of volcanic activity peaked around 60 million years ago and again near 55 million years ago. Magmatism occurred mainly in the early Palaeocene within the British and Northwest Atlantic volcanic provinces. Northeast Atlantic magmatism happened during the early Eocene when spreading directions changed in the Labrador Sea. A proto-Icelandic mantle plume rose beneath the Greenland lithosphere approximately 65 million years ago. Flood basalts erupted across Ethiopia, northeast Sudan and southwest Yemen as the Afar mantle plame impacted the African lithosphere in the early Oligocene. These events coincided with the intersection of propagating rifts and pre-existing lithospheric structures that acted as channels for magma to reach the surface.
Global mean surface temperatures increased to 31.6 degrees Celsius during the Paleocene-Eocene Thermal Maximum. This warming event lasted from about 56 to 48 million years ago and was ten to fifteen degrees higher than current annual means. Rapid release of frozen methane clathrates from seafloor sediments drove this intense greenhouse condition. By the late Eocene around 37 million years ago, ice sheets formed in Antarctica. Changes in deep ocean currents opened the Drake and Tasmanian passages, establishing the Antarctic Circumpolar Current. Dense polar waters sank into the deep oceans and moved northwards, reducing global ocean temperatures. The Early Oligocene Glacial Maximum lasted for about 200,000 years while global sea levels dropped significantly. Tropical forests were replaced by dry woodlands and widespread grasslands by the early Oligocene.
Mammals evolved from small generalized forms into most modern varieties after the Cretaceous-Paleogene extinction event. Some mammals became large land dominators while others adapted to marine environments as cetaceans and sirenians. Primates appeared on land bridges across the Bering Straits when sea levels fluctuated during low stands. Birds took over skies left empty by extinct pterosaurs, with flightless groups like penguins and ratites filling new niches. Myctophids first appeared in the Late Palaeocene or Early Eocene before expanding their range into open oceans. Grasses and herbs such as Artemisia began to proliferate at the expense of tropical plants during pronounced cooling in the Oligocene. Conifer forests developed in mountainous areas as major floral shifts occurred throughout the period.
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Common questions
What marks the start of the Paleogene period?
A 50 cm thick layer of rusty colored clay at Oued Djerfane in Tunisia marks the start of the Paleogene period. This thin band contains an iridium anomaly from a massive asteroid impact deposited over just a few days around 66 million years ago.
When did India collide with Tibet to form the Himalayas during the Paleogene?
India collided with Tibet around 55 million years ago after drifting northward at roughly 18 cm per year. This collision produced the Himalayas through the scraping of metasedimentary rocks off the Indian continental crust.
Where is the crater located that caused the boundary between the Cretaceous Period and the Paleocene Epoch?
The crater lies buried under the Yucatan Peninsula in Mexico. Similar layers appear worldwide containing microtektites and shocked quartz that confirm the extraterrestrial collision.
How long did the Paleocene-Eocene Thermal Maximum last and what was its temperature increase?
This warming event lasted from about 56 to 48 million years ago and reached global mean surface temperatures of 31.6 degrees Celsius. The condition was ten to fifteen degrees higher than current annual means due to rapid release of frozen methane clathrates from seafloor sediments.
Which mountain chains formed when Africa collided with Eurasia during the early Paleocene?
Africa collided with Eurasia to form the Alpine-Himalayan mountain chains including arcuate ranges stretching from the Tell-Rif-Betic cordillera to the Taurides. Subduction zones developed along the western Mediterranean where the European plate moved beneath Africa by 40 million years ago.