310 million to 245 million years BP : Pennsylvanian to Permian
The Pennsylvanian Period began around 310 million years ago. Dropping global
temperatures culminated in an ice age beginning around 300 million BP and ending
in the middle of the Permian Period. The North American continent then was probably
centered on the equator, placing this area just south of the equator. A tropical climate
persisted here on a fairly level land mass near sea level. The Appalachian Mountains
were still uplifting, and the Ozark dome had begun to rise in the east. At this time large
basins existed to the northeast, northwest, south, and southeast of the Ozark Dome.
Lower Pennsylvanian deposits are sparse in Newton and McDonald Co.s, Mo., but the
Morrowian Series Hale and/or Graydon sandstone formations may be found in pockets.
Hale sandstone caps some hills in southwest Barry Co., and can be seen at the top of
the exposure on Oakleigh Mountain. There, it is a brown sandstone lying on top of a
shale pellet conglomerate and containing many plant fossils.
Northeast Oklahoma has Pennsylvanian shale deposits of a few feet to over 200 feet,
thinning near the Missouri border. A very small volume of thick residual oil occurs locally
in these shale deposits. These appear to be primarily Middle Pennsylvanian Desmoinesian
Series deposits including the Weir-Pittsburg, Cherokee (mostly), and Marmaton coals.
Vesicaspora species spores have been found in these and an examination of the Drywood
Formation fossil flora, of the same time, found in neighboring counties to the north and
east of this area has identified 11 species of the Lepidodendrales order, 11 species of the
Equisetales order, 3 species of the Sphenophyllales order, 29 species of the Filicales and
Cycadofilicales orders, and 7 species of the Cordaitales order.
The Middle Pennsylvanian deposits are the last I am aware of in this section up until
the Pleistocene glacial deposition. This is a period of over 290 million years. Inferences
only, from neighboring geology and paleontology, will let us recreate these times.
Cotylosaurs appeared around 300 million BP and became the first vertebrates to lay
their eggs on land. Dinoflagellates, coelacanths, and mesosaurs invade the seas, land
snails, daddy longlegs, cockroaches, salamanders, pre-frogs, and Dimetrodon invade the
lands, and true ferns, horsetails, conifers, and bisaccate pollen appear in the flora of the
The final period of the Paleozoic Era, the Permian Period, began around 280 million
years ago. The earliest bipedal reptile, found in central Germany, has been dated to
280 million years BP, and early Permian remains from Las Cruces, New Mexico, indicate
the evolution of giant reptiles, mammal-like reptiles, and horseshoe crabs. The Permian
Period produced the monstrous crocodile-like reptiles like the pelycosaur and the
ichthyosaur, while a reef deposit built up in New Mexico later to become Carlsbad Caverns.
Other new creatures of the Permian include dragonflies, crickets, mayflies, beetles, flies,
cicadas, leafhoppers, and pre-turtles. It was a cooler, dryer period early on and the
conifer was probably the most common tree here. Global temperatures began rising in the
middle Permian producing warmer, dryer, and possibly desert conditions in this area. Near
the end of the Permian, average global temperatures spiked beyond any others we have
indications of, possibly to around 24 degrees C. For contrast, current global average
temperatures are around 13-14 degrees C., and other warm periods in earth's history
appear to have only reached 22 degrees C. At the end of the Permian and the close of the
Paleozoic Era, continental uplift occurred, and the Ozark region and the Ouachita Province
of Arkansas and Oklahoma have since been a continuous land area with concomitant plant
evolution. Rising temperatures and loss of habitat through uplift may have contributed
to the mass extinction occurring around 250 million BP in which 54% of living families
and over 90% of animal species, mostly marine invertebrates, perished. Trilobites, Rugosa
corals, Tabulata corals, and the Blastoidea, to name a few, disappeared from the fossil
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