Paleocene Epoch: Life and Earth in the Wake of Mass Extinction

The Paleocene was a transformative epoch that marked the beginning of the Cenozoic Era. Spanning from approximately 66 to 56 million years ago (Ma), it served as a critical period of recovery and biological reorganization following the devastating Cretaceous–Paleogene (K–Pg) mass extinction event. During this time, the Earth transitioned from the age of dinosaurs into a world where new lineages of mammals, birds, and plants began to dominate the landscape.

Named by Wilhelm Philipp Schimper in 1874, the Paleocene represents a foundational chapter in modern Earth history. It was a time of shifting continents, changing climates, and the rapid evolutionary radiation of species that would eventually shape the modern biosphere.

A realistic black-and-white portrait of Schimper, who had a full beard and mustache, sideburns, a receding hairline, and is dressed in a formal jacket and bowtie — Wilhelm Philipp Schimper coined the term "Paleocene".

Geological Foundations and Boundaries

A tropical environment with a lake, palm trees and conifers, and in the background a tall mountain — Restoration of a Patagonian landscape during the Danian

The Paleocene is defined by distinct geological markers that separate it from the preceding Cretaceous period and the succeeding Eocene epoch. The lower boundary is marked by an iridium-enriched layer, a chemical signature resulting from the massive meteorite impact that triggered the K–Pg extinction.

A dark brown slab of rock with a whitish stripe across the middle — K–Pg boundary recorded in a Wyoming rock (the white stripe in the middle)

Stratigraphically, the epoch is divided into three distinct ages:

Danian: The earliest stage of the Paleocene.
Selandian: The middle stage.
Thanetian: The final stage before the transition to the Eocene.

The upper boundary of the Paleocene is defined by a significant geochemical shift known as a strong negative anomaly in δC values (carbon isotope values) during the Paleocene–Eocene Thermal Maximum (PETM). This event was a period of rapid global warming that significantly impacted both terrestrial and marine ecosystems.

The ocean to the left, gentle tides coming in, a small piece of sandy beach before the white cliffs rise with grass on the top — The sea cliffs of Itzurun beach near the town of Zumaia, Spain, the GSSP for the Selandian and Thanetian

Paleogeography and Tectonics

During the Paleocene, the map of the world looked vastly different than it does today. The supercontinent Gondwana continued its fragmentation, and the movement of tectonic plates reshaped ocean currents and landmasses.

Four maps depicting the separation of Madagascar from India — The breakup of Gondwana: A) Early Cretaceous B) Late Cretaceous C) Paleocene D) Present

In North America, the Laramide orogeny—a major mountain-building event—was actively occurring. This process was driven by the subduction of oceanic crust beneath the North American Plate, creating the complex geological structures seen in the region today.

A diagram of the Pacific Plate being subducted under the North American Plate — The Laramide orogeny was caused by the subduction of oceanic crust under the North American Plate

The era also saw significant volcanic and impact activity. For instance, evidence suggests that the crater located beneath the Greenlandic Hiawatha Glacier dates back to the Paleocene, approximately 58 million years ago.

The crater underneath the Greenlandic Hiawatha Glacier dates to the Paleocene, 58 mya.[40]

Climate and Environment

The Paleocene climate was characterized by significant fluctuations. While the early part of the epoch saw a recovery from the post-impact world, the period culminated in the PETM, an interval of extreme warmth. This warming had profound effects on ocean ventilation, oxygenation, and biological productivity.

On land, the environment varied from lush tropical rainforests to polar forests. In regions like present-day Colombia, the Cerrejón Formation provides evidence of early Neotropical rainforests. These environments were rich in organic matter, often resulting in significant coal deposits.

Paleocene coal is extracted at the Cerrejón mine, Colombia's largest open-pit mine

The flora of the Paleocene was diverse, featuring a mix of surviving Cretaceous lineages and emerging angiosperms (flowering plants). Notable plant fossils include species of Ginkgo, Glyptostrobus, and Metasequoia, which thrived in the varied climates of the era.

Reconstruction of the late Paleocene Ginkgo cranei

A slab of gray rock featuring several thin branches with thistle-like leaves — The conifer Glyptostrobus europaeus from the Canadian Paskapoo Formation

A slab of gray rock with a dark-reddish brown fruit imprint featuring fronds around its circumference — Fossil Platanus fruit from the Canadian Paskapoo Formation

A slab of gray rock with a darker gray evergreen branch fossil — Metasequoia occidentalis from the Canadian Scollard Formation

The Rise of New Life: Fauna of the Paleocene

With the disappearance of non-avian dinosaurs, ecological niches became available, leading to an evolutionary radiation of various groups.

Mammalian Evolution

Mammals underwent rapid diversification. Early Paleocene mammals included large herbivores like the pantodont Barylambda, which could weigh up to 650 kg. Other notable groups included the mesonychids, such as Sinonyx, and the early ancestors of modern placental mammals.

Portrait view of a heavily built 4-legged animal with a strong tail — Restoration of the herbivorous late Paleocene pantodont Barylambda, which could have weighed up to 650 kg (1,430 lb)[139]

Portrait view of a wolf-like skeleton with large teeth — The mesonychid Sinonyx at the Museo delle Scienze

Birds, Reptiles, and Marine Life

Birds also saw significant morphological diversification. Large, flightless birds like Gastornis were prominent features of the landscape. In the oceans, new lineages of fish and sharks, such as the early trumpetfish and the shark Otodus obliquus, began to establish themselves.

A big bird with blue-gray feathers, a white underbelly, and a large, parrot-like, red beak — Gastornis restoration

Topside view of a crocodile skeleton — Borealosuchus at the Field Museum of Natural History

The top half is a rock slab featuring an oblong, orange-brown fish impression, and the bottom half is an illustration highlighting the armored scutes on its body — The early Paleocene trumpetfish Eekaulostomus from Palenque, Mexico

A brown shark toothed with top part lodged in a rock — Otodus obliquus shark tooth from Oued Zem, Morocco

Invertebrates and insects also played vital roles in the ecosystem. From the dominant reef-building organisms of the previous era to the diverse insect populations found in formations like the Danish Fur Formation, the Paleocene was a period of intense biological activity.

Earwig from the late Paleocene Danish Fur Formation

A slab of rock with a faint impression of an ant — The ant Napakimyrma paskapooensis from the Canadian Paskapoo Formation

A rudist, the dominant reef-building organism of the Cretaceous

Key Facts

Time Span: Approximately 66 to 56 million years ago.
Etymology: The term was coined by Wilhelm Philipp Schimper in 1874.
Boundary Marker: The lower boundary is defined by an iridium-rich layer from a meteorite impact.
Major Climatic Event: The Paleocene–Eocene Thermal Maximum (PETM) caused rapid global warming.
Biological Trend: A period of rapid evolutionary radiation for mammals and birds following the K–Pg extinction.

Summary of Paleocene Chronology

Paleocene Epoch Overview
Age	Period/Epoch	Key Characteristics
Thanetian	Late Paleocene	Final stage before the Eocene; includes the PETM event.
Selandian	Middle Paleocene	Intermediate stage of recovery and diversification.
Danian	Early Paleocene	Immediate aftermath of the K–Pg mass extinction.

Frequently Asked Questions

What event marks the beginning of the Paleocene?

The Paleocene begins with the K–Pg (Cretaceous–Paleogene) mass extinction event, which is geologically identified by an iridium-enriched layer caused by a major meteorite impact.

How did the climate change during this epoch?

The climate underwent significant changes, most notably during the Paleocene–Eocene Thermal Maximum (PETM), which was a period of intense global warming marked by a strong negative carbon isotope anomaly.

What kind of animals lived during the Paleocene?

The Paleocene saw the rise of many mammal lineages, including large herbivores like Barylambda, as well as various birds, reptiles, and diverse marine life like sharks and trumpetfish.

What was the role of plants in the Paleocene ecosystem?

Plants were essential in rebuilding the terrestrial ecosystems. The era featured diverse flora, including early rainforests and various angiosperms, which provided the foundation for the recovering food webs.

What is the GSSP?

GSSP stands for Global Boundary Stratotype Section and Point. It is a internationally agreed-upon reference point on a stratigraphic section which defines the lower boundary of a stage or epoch.