65 million to 2 million BP : Paleocene to Pliocene

 

 

       The Cenozoic Era began around 65 million years ago and continues into current

times. The Tertiary Period encompasses the Cenozoic Era through the Pliocene Period.

As the Mesozoic is considered the Age of Dinosaurs, the Cenozoic is considered

the Age of Mammals. Following the demise of the dinosaurs, mammals proliferated and

became the worlds most fearsome carnivores. Uplift of the Great Plains occurred early

in the Tertiary while the Mississippi embayment persisted and peneplanation leveled the

Ozarks. A broad-leaved forest then existed from the still rising Rockies to the east

coast. Through most of the Tertiary, the Ozarks were a vast, low, forested plain with

slow streams and swamps. Ozark flora then included Acer rubrum var. Drummondii,

Acer saccharum, Alnus genus, Amelanchier genus, Arundinaria gigantea, Berchemia

scandens, Bumelia lanuginosa var. oblongifolia, Carpinus genus, Carya aquatica, Castanea

genus, Cephalanthus occidentalis var. pubescens, Cercis canadensis, Chionanthus virginica,

Cladrastis lutea, Cornus foemina, Cornus florida, Corylus genus, Cotinus obovatus,

Crataegus genus, Diospyros virginiana, Fagus genus, Fraxinus tomentosa, Gleditsia

aquatica, Ilex decidua, Itea virginica, Juglans genus, Leitneria floridana, Lindera benzoin,

Nyssa aquatica, Ostrya genus, Pinus genus, Planera aquatica, Platanus genus, Populus

heterophylla, Prunus genus, Quercus lyrata, Q. michauxii, Q. nigra, Q. phellos, Rhus genus,

Salix genus, Sassafras albidum, Styrax americana, Taxodium distichum, Tilia genus,

Ulmus genus, Viburnum rufidulum, and Wisteria macrostachya. Our present persimmon

is closely related to the Tertiary large-leaved persimmon, and the Cotinus genus of the

Tertiary Period shows very little difference between fossil and living leaf structure.

     The Paleocene Period is the first of the Cenozoic series. These were usually geologically

quiet, dry, and tropical times but around 60 million BP, India collided with Asia creating

the Himalayan Mountains. The ancestors of the monkeys, the lemuroids, appeared in the

Paleocene. The Eocene Period follows, beginning around 58 million BP. It was warm and

sub-tropical globally, and the lower Eocene in our area was a warm, humid coastal

plain with adjacent highlands in Arkansas. Cladrastis eocenica may have existed in this

area in the Eocene Period. At around 50 million BP, another mass extinction occurred. The

Pacific Ocean Emperor seamounts rose around 48 million BP, and the Pacific plate itself

was turning northwest by 43 million BP. At 40 million BP, a land bridge reached from South

America thru Antarctica to Australia, across which the beech tree possibly spread. During

the Eocene Period, the whale family moved into the sea. 55 million year old whales in

Pakistan still possessed four legs while those 40 million years old from Egypt had only

pelvic feet. Primitive monkeys appeared during the Eocene, and by 45 million BP, a

mouse-sized primate lived in China. The oldest flowering plant amber or resin has reached

us from 53 million BP containing moths, flies, flowers, and leaves of the period. The

Eocene Period also produced butterflies, bats, camels, the class Nematomorpha, Eohippus -

the forerunner of the horse, and the belemnites became extinct. By the end of the Eocene

Period, this area probably occupied its current geographical space.

       Around 38 million BP the Oligocene Period began. It had a warm, temperate

climate, and was a geologically active period with much uplift and tilting. The Midway

Islands were raised around 28 million BP. The mastodon dates back to this period.

The Miocene Period began around 24 million BP. It had a temperate climate and,

at least toward the end, was a geologically active period. Global uplift occurred,

primarily as linear upwarpings, which left us with a rolling or undulating landsurface

above the younger incised valleys. Since about 20 million BP, the continents have been

largely high and dry because of extensive uplift and permanent significant ice at the

poles. 19 million years ago land mammals first appear in the West Indies on Cuba as

primates, sloths, and rodents, and around 16 million years ago another large asteroid

blasted part of the Martian crust out into space. The middle Miocene formations in North

America have produced mastodons. Porpoises first appear during the Miocene Period.

       Till late in the Tertiary, this area was part of a low-lying, wet, peneplain with

bald cypress, sweet gum, and possibly Quercus nigra, Q. phellos, Q. michauxii, Populus

heterophylla, Fagus caroliniana, Planera aquatica, and Ilex opaca. Then the Ozarks were

again uplifted producing its present high and dry physiology and restricting the bald

cypress and sweet gum to the extreme southeast corner of Missouri. The Great Plains

region uplifted at about the same time and the Boston and Ouachita mountains uplifted

soon after. Peneplanation again followed which can be seen as accordant levels of the

summits of hills, and then producing wide meander valleys. The course of current streams

were then determined, and a final slight uplift later produced the wide, deep valleys.

Tertiary "Lafayette" gravels cap low-lying hills in the Miami, Oklahoma area.

       The Pliocene Period began around 8 million BP with continuing uplift. This was

followed by denudation which produced most of today's non-glacier landscape of

basins, lowlands, and coastal and interior plains. Around 6 million BP, Europe and

Africa collide creating a Paleo-Mediterranean Sea. It dried up around 5.6 million BP,

until the Straits of Gibraltar opened around 4.9 million BP. 5.1 million BP the Kauai

islands were raised. It is most commonly accepted that the hominids split from apes

somewhere between 7 and 5 million years ago. The earliest (so far) direct evidence of

early hominids is the teeth of Australopithecus afarensis in Ethiopia dated to between

4.5 and 3.7 million BP. Next is the Ardipithecus ramidus fossils from 4.4 million BP,

also from Ethiopia. A. anamensis follows at 4.1 million BP in Kenya. Around 4 million

BP the Grand Canyon in Arizona began to grow. A. afarensis footprints in Tanzania date

back to 3.6 million years and the same species in Ethiopia between 3.4 and 3 million

BP was involved in a volcanic eruption which also buried juniper and olive tree forests,

elephants, babboons, pigs, rodents, and monkeys. Lucy, a famous representative of the

A. afarensis lived in Ethiopia around 3.18 million years ago. Australopithecus africanus

found near Johannesburg dates to 2.8 million BP, and Australopithecus aethiopicus

from Ethiopia dates to 2.6 million BP. The earliest stone tools found date back to

2.6 million years ago. Homo genus fossils from Malawi and Kenya date back to 2.4

million BP, while a Homo jawbone from Ethiopia is 2.3 million years old. The end of

the Pliocene Period was geologically active with upheavals placing the mountains at

their present heights.

 

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REFERENCES

    Asimov, I., 1987, Beginnings: The Story of Origins.

    Fenton, C.L., Fenton, M.A., 1958, The Fossil Book. Doubleday

    Hunt, C.B., 1986, Surficial Deposits of the United States.

    King, L.C., 1983, Wandering Continents and Spreading Sea Floors on an Expanding

         Earth. John Wiley and Sons

    National Geographic

    Netzeband, W.F., General Geology of the Tri-State District--Missouri-Oklahoma-Kansas

    Paleomap Project

    O'Brien, M.J., 1996, Paradigms of the Past, Missouri Archeology.

    O'Brien, M.J., Wood, W.R., 1998, The Prehistory of Missouri. University of Missouri Press

    Stearn, C.W., Carroll, R.L., Clark, T.H., 1979, Geological Evolution of North America.

         John Wiley and Sons

    Steyermark, J.A., 1959, Vegetational History of the Ozark Forest. University of

         Missouri Studies, vol.31

    Tschudy, R.H., Scott, R.A., 1969, Aspects of Palynology. John Wiley and Sons

 

 

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