Virginia 35 Million Years Ago
What Was the Eocene Epoch?
Research shows that the Chesapeake meteorite slammed into the earth approximately 35 million years ago during the Eocene Epoch, the second epoch of the Cenozoic era. This time epoch started about 56 million years ago and lasted until about 33.8 million years ago. The continents continued to move during the Eocene. A large island (that is now India) met the continental mass of Asia and created what would become the Himalayan mountain range. North America separated from Europe, and Australia and South America broke away from Antarctica and migrated northward. The Eocene is regarded as the warmest epoch of the Tertiary Period. Subtropical conditions could be found up to the Arctic Circle at the start of the epoch. Toward the end of the epoch, temperatures began dropping significantly.
Eocene Plant life
Much of the understanding of the plant communities of the Eocene of Virginia comes from the study of Paleopalynology. This is the study of organic-walled microfossils. Usually this means fossil plant pollen and spoors, and in marine environments, single-celled algae. Paleopalynology is useful for relative age dating (biostratigraphy) and for determining past environments. Its greatest advantage is the small sample size (about 10 grams), which makes it ideal for studying rock from drill holes.
Dr. Norm Fredericksen of the USGS examined slides of pollen form the Chickahominy Formation (upper Eocene) in the Langley core from Hampton, Virginia, and made the following observations of the pollen samples:
In the area associated with the meteorite impact there was a mix of tropical and subtropical species of plants. Many, perhaps most, flowering plants species were insect-pollinated and, therefore, the amount of wind-pollinated pollen is large in proportion to the real abundance of those plants. One of the most typical pollen grains of the Eocene is a member of the walnut family. It was extremely widespread in the Northern Hemisphere in the Eocene, but then it died out in most of the world and is now found only in Mexico and Central America. A number of palm pollen types are know from the upper Eocene of the eastern U.S. It is safe to say there were many species of palms present in Virignia in the late Eocene. Pines, while producing prodigious amounts of pollen, are not as abundant in samples suggesting that pines did not grow abundantly on the coastal plain but rather probably lived at the time mainly in the mountains. One of the most abundant pollen types in the Chickahominy Formation was oak pollen. Wind-pollinated and produced in huge amounts, this indicates that oaks were abundant on the coastal plain.
During the Eocene, the first grasses originated and with them a host of grass-living animals. Because new growth of these grasses occurred near the root rather that the tip of the plant, the plants could quickly recover from damage caused by grazing and fire, creating a renewable resource for rapidly evolving plant-eaters. An explosion in varieties of flowering plants just before, during, and after the Eocene populated the land with many new species of trees, shrubs, and small plants. A variety of trees thrived in the warm Eocene climate including beech, elm, chestnut, redwood, birch, and cedar among others.
(Drawings of plants will be posted by September 20, 2002.)
Eocene Animals and Photo Gallery
The richness and variety of the animals that populated the Eocene world is staggering. Increasingly warm conditions at the start of the Eocene caused the extinction of some of the prominent species of the prior epoch, the Paleocene. But, overall, land mammals flourished as new species diversified and adapted. In particular, mammals with keen senses of smell thrived in the dense forests and warm conditions, even around the Arctic Circle, which in turn enabled these species to migrate between North America and Europe via Iceland and Greenland.
The Eocene saw the appearance of a number of direct evolutionary ancestors of modern animals. The ancient hoofed condylarths gave way to more modern ungulates and became extinct before the end of the epoch. The modern hoofed mammals -- perrisodactyls and artiodactyls -- of Europe, Asia and North America, including proto-horses chalicotheres and rhinoceros-like Titanotheres, were all small to begin with, about the size of a modern domestic cat. However, some groups, especially the Titanotheres, quickly grew to a huge size, before dying out in a mass extinction of archaic forms at the end of the Eocene.
Rodents replaced the multituberculates in the small gnawing herbivore group. Bats, like the modern types, appeared and evolved from primitive Insectivore. The first aquatic mammals, whales, and sea cows appeared in the oceans. The Eocene saw the appearance of modern birds such as eagles, pelicans, quail, and vultures as well a the great flightless Diatriyma, two meters or more in height, with a huge hooked beak that clearly indicated carnivore habits. During this epoch, the first primates that resemble living species evolved. By the end of the epoch most of the modern orders of mammals had evolved. In addition to these modern looking species, many archaic species still roamed the landscape. Mammals emerged as the dominant land animals and some orders reached their end during this epoch. Here we can only take a brief look at the more remarkable types -- those mammals that would surely have caught our eye had we been on a safari in the Eocene world.
|Moeritherium, earliest known proboscideans.||
(Drawings of animals will be posted by September 20, 2002.)
EOCENE ACTIVITY NO. 1
|Ongoing Research at Smithsonian Institution, Museum of Natural History|
TITLE: TROPICAL VIRGINIA
Students will become aware of the relationship of climate to plant life as might have been found in Virginia during the late Eocene Epoch of 37-33.8 million years ago.
The climate of a place determines the types and varieties of plants. Virginia during the late Eocene Epoch had an unusual mixture of tropical and subtropical elements. Plant fossils and pollen analysis indicate that Virginia was a place of heat and humidity similar to Florida and the Gulf Coast of Mexico. Just why this was the case is a difficult question to answer. Scientists are piecing together prehistoric climates by the clues left by fossils.
Research materials on the plants of Florida and coastal Mexico
- Research and identify the climates of Florida and Coastal Mexico.
- Collect and press examples of plants that are still found in your locality that are representatives of plants found during the late Eocene.
- Make a chart of the different types of plants that still may be found.
- Create a bulletin board entitled "Plants of the Late Eocene".
EOCENE ACTIVITY NO. 2
TITLE: EOCENE ASTROBLEMES
To have students locate on an Eocene world map the major Eocene meteorite impacts.
Probably the most dramatic geological event that ever took place on the Atlantic margin of North America occurred about 35 million years ago in the late Eocene Epoch. The ancient shoreline of the Virginia region was somewhere in the vicinity of where Richmond is today.
Astroblemes are the remaining craters and other structures where meteorites have hit Earth. More than 150 locations have been identified throughout the world.
Most craters wider than 10 km are classified as complex craters, because they exhibit unique structural features. Like simple craters, a raised rim marks the outer margin of complex craters. Inside the rim is a broad, flat circular plain called the annular trough. Large slump blocks fall away from the crater's outer wall and slide out over the floor of the annular trough toward the crater center. The inner edge of the annular trough is marked by central mountainous peak, a ring of peaks (a peak rink), or both. Inside the peak ring is the deepest part of the crater called the inner basin.
The general public is intensely interested in meteorite impacts and the resulting astroblemes. The Shoemaker-Levy 9 comet hit Jupiter in 1994, and the news captivated viewers worldwide. Also, theories that the a particularly large meteorite -- the Chicxulub -- is thought to have contributed to the demise of dinosaurs have been prominent in the news.
Lately, we have come to realize that a large meteorite htting the Earth could cause global environmental devastation and the mass extinction of animal and plant species. A meteorite impact results in a super-hot blast wave, a base surge of hot debris, gigantic tsunami waves, vaporization of a water column and target rocks, and giant earthquakes in a regional area.
On a global scale, short-term effects could include fallout of ejected particles and raging wildfires. Long-term effects include prolonged darkness due to atmospheric debris, acid rain, and greenhouse warming.
A few astroblemes date to the Eocene Epoch. They are located at:
|Fossils from Green River Formation, Wyoming|
- The Chesapeake Bay
- Logancha, Russia
- Belorus, Russia
- Labrador, Canada
- Sudbury, Ontario, Canada
- Popigai, Russia
A map of the Eocene World [Click here for .pdf file of the Eocene World Map. The hatched line shows the shape of the continents during the Eocene Epoch.]
A world atlas
Reproduce the Eocene World map
Locate each of the astroblemes listed above by conducting an Internet search of "meteorite impacts"
Research the Shoemaker-Levy 9 impact event on Jupiter
Research the Torino Scale, which is a scale that measures the damage caused by meteorites
This Web site provides an excellent summary of the Geologic Time Scale.
Here is a short summary of the Eocene epoch with some excellent links.
University of California Museum of Paleontology
The Eocene epoch is part of the Tertiary Period in the Cenozoic Era. This Web site provides thorough information on the stratigraphy, ancient life, localities, and tectonics related to the Eocene.