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A crude story Hooray for decay!
The decay of organic stuff -- life -- accounts for the fossil fuels coal, gas and oil. What kind of plants and animals sacrificed their bodies so we can burn gasoline in our cars and natural gas in our furnaces?

Don'tcha worry none, we're not going to attempt to Cliff-Note the entire natural history of fossil fuels on a single web page. But we do want to showcase some of the fascinating organisms that developed when lots of future oil and gas was being deposited.

Want more on evolution the process that explains the diversity of life?

(click on the "thumbnail" images below (along the right side of the page) to see a full-size diorama of that time period)
Miocene & Oligocene

The Miocene (5 million years ago -- mya -- to 23 mya) and the Oligocene (23 mya to 34 mya) Epochs provided about 12.5 percent of known oil and gas deposits.

During the Miocene, grazing mammals increased and proliferated. In this bear-dog eats three-horned ruminant world, both grazers and predators gained speed to improve their chances for survival on the grasslands.

thumbnail size image of a scene in the oligocene epochOligocene
The Oligocene was marked by a blossoming of the mammals. It also contains the first records of marsupials, in Australia.

thumbnail image of crinoidsCretaceous
The Cretaceous Period, from 141 mya to 65 mya, was dominated by dinosaurs, which were presumably destroyed by an asteroid impact at the end of the era. The middle Cretaceous saw major deposits of organic material that would form oil and gas. About 29 percent of the total supply was laid down between 119 mya and 88.5 mya.

thumbnail image of an imprint of a horseshoe crabJurassic
During the Jurassic (202 mya to 141 mya), dinos ruled, mammals drooled, and the continents were welded into the supercontinent Pangea. About 25 percent of total oil and gas accumulated during the Jurassic, between 169 mya and 144 mya.

Permian & Pennsylvanian
During the Permian (290 mya to 250 mya) and Pennsylvanian (323 mya to 290 mya) Periods, the organic material for 8 percent of today's oil and gas was deposited.

thumbnail image of a shallow Permian seaPermian
The therapsid dinosaurs that would later evolve into mammals appeared in the Permean. These carnivores had differentiated teeth and separate nostrils. The Permean Period ended with a huge asteroid impact 250 mya that exterminated 96 percent of all living species. Got that hard hat?

thumbnail image of Pensylvanian Period dragonfliesPennsylvanian
The swampy forests of the warm, damp Pennsylvanian Period supplied major coal deposits and lots of fossils. Trees grew 100 feet tall, and some ferns reached 50 feet -- five stories -- in height. Bizarro animals included meter-long cockroaches and the first reptile.

Mississippian & Devonian
Between 374 mya and 352 mya, about 8 percent of conventional oil and gas were deposited. The deposits occurred during the Mississippian (363 mya to 323 mya) and Devonian (409 mya to 363 mya) Periods.

thumbnail size image of crinoid fossilMississippian
In the Mississippian, land was gathered into two large continents. The northern continent, comprising North America, Europe and Asia (less India) was called Laurasia, and was surrounded by seas filled with crinoids (shown above).

thumbnail image of a spiked trilobite crawling along the sea floorDevonian
The first sharks and bony fishes emerged during the Devonian, along with the first seed-bearing plants. Amphibians moved to land, becoming the first vertebrates to know the pleasure of stepping onto solid ground. Take it from us: Terra firma feels great if you've been seasick for a hundred million years...

thumbnail image of the silurian period...underwater...a virtual silurian reefSilurian
During the Silurian Period (439 mya to 409 mya), about 9 percent of oil and conventional gas were deposited. Meanwhile, life was busy test-driving a number of cool inventions. Aquatic plants made ozone, offering protection from the sun's ultraviolet rays and allowing organisms to abandon the protection of the sea and head for dry land. Insects evolved -- leading to endless cussing over house flies and mosquitoes. The first plants with vascular channels -- pipes that carry water and nutrients -- appeared. Fish with jaws arose (all the better to eat you with, my dear) which eventually spawned modern vertebrates.

Back to the subject: How do they find oil left by these creatures, anyway?


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