Skip to main content.

Smithsonian National Museum of Natural History
{search_item}

Department of Paleobiology

The K/T Boundary

Sixty-five million years ago the curtain came down on the Age of Dinosaurs when a cataclysmic event led to mass extinctions of life. This interval of abrupt change in Earth's history, called the K/T Boundary, closed the Cretaceous (K) Period and opened the Tertiary (T) Period.

This deep-sea core provides convincing support to the hypothesis that an asteroid collision devastated terrestrial and marine environments world-wide. It also shows a record of flourishing marine life before the event, followed by mass extinction and then evolution of new species and slow recovery of surviving life forms after the event.

NMNH micropaleontologist Dr. Brian Huber was among the team of scientists aboard the drill ship, Joides Resolution, that recovered the core in January 1997. He arranged with JOI (Joint Oceanographic Institutions) to place a section of the core on display in the Museum. More information about the drill ship may be found at the Ocean Drilling Program's web site.

The Core

By analyzing and dating the contents of each layer in the deep-sea core, scientists have reconstructed what happened one day 65 million years ago. Much of the story is told by foraminifera, single-celled organisms that have inhabited the oceans for more than 500 million years. You can compare pictures of the foraminifera from before the impact and after the impact here. Also present in the core were Tektites (see photos below.


Tiny Creatures Tell a Big Story

Foraminifera are single-celled organisms that have inhabited the oceans for more than 500 million years. Both living and fossil foraminifera come in a variety of shapes and sizes and occur in many different marine environments--from the shoreline to the deep sea, from near the surface to the ocean floor. Their abundance, wide distribution, and sensitivity to environmental variations make them good indicators of past climate change.

Notice the tremendous difference in size between the foraminifera shown in these two microscope photos of the pre- and post-impact sections of the core.

The above photo shows pre-impact foraminifera from the Cretaceous Period. Large, ornate foraminifera flourished. Sampled from 2 cm below the K/T tektite layer.

The photo above shows the post-impact foraminifera from the Tertiary Period. Only tiny, less ornate foraminifera survived; a few new species evolved. Sampled 1 cm above the K/T ejecta layer.

Tektites are glassy material condensed from the hot vapor cloud produced by the impact which rained down and accumulated in a distinctive layer within the core.

Continue to Interview, References, and Related Sites ...

SEM images by Dr. Brian Huber

[ TOP ]