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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