15 billion to 570
million years before present : Beginning to Ediacaran
History is the available record of past
observations. Prehistory envelopes all other past occurrences. All that is
known of prehistory is implied knowledge through the extrapolation of cause and
effect, or more simply, common sense. A leaf seen lying on the porch implies
its prehistory of growth and transport. Over time, humanity has developed many
tools which aid this extrapolation, such as writing, mathematics,
magnification, chemical analysis, stratigraphy, etc. Refinements in techniques
are constantly occurring which alter slightly our picture of the past hopefully
toward the more factual. This writing is an attempt to report what has been
surmised of the prehistory of the land area now situated between latitudes
36-37 north and longitudes 94-95 west (includes the corners of southwest
Missouri, northwest Arkansas, and northeast Oklahoma), as well as events which
occurred in the rest of the world and universe that may have impacted this
area.
Speculation and conjecture on events prior to the establishment of the
form of our universe, and the will and/or natural
forces instigating it, are currently beyond the scope of generally agreed upon
prehistory. Therefore, we start with the theory of the Hot Big Bang. It begins
with the assumption that everything in the universe was originally contained in
an extremely small volume. About 13.5 billion years ago, Planck's constant, or
the mathematical relation we see between matter and energy, became a physical
law and force of its own. If this number were different to any degree, matter
and energy would act differently. Once this relation was determined, the other
physical laws and entities should appear in a logical order. First, the basic
gravity of the universe becomes a necessary force, then the force which repels
or separates, appears. These forces together produce heat and pressure
requiring expansion. As the universe expands, pressure and temperature drop,
and particles and/or waveforms, begin to form. The smallest entities - quarks,
antiquarks, electrons, and other exotic particles, form first. Their production
induces electromagnetism and the weak force of radioactivity to become powers.
Further expansion allows protons and neutrons to form and become nuclei
producing matter. Matter and energy then amass gravities of their own as they
separate and clump together, and in time, produce galaxies. Universal expansion
continues today at a rate of about 75 kilometers/second, and can be seen to
have occurred much faster as we look into the past while sensing light which
left galaxies millions and billions of years ago.
Thus, the Milky Way, our home galaxy, was probably born 10-12 billion
years ago. Its early existance, while containing virtually the same mass in a
much smaller volume, was probably quite spectacular. Collisions of stars, and
novas igniting supernovas were likely much more common. It appears that our
system was born of a nebula produced by stars which became supernova. The
oldest, hands-on, chemical isotope dating has placed the time of formation of
some meteorites and their contents in this pre-solar system era. The Hadean
Eon, the oldest division of geologic time, began then, and the Precambrian Era
encompasses all geologic time prior to the Cambrian.
Our solar system took shape 4.6 billion years ago. Initially molten, the
earth slowly cooled while undergoing a dwindling bombardment over the next 600
million years. By 4.4 billion BP (Before Present), most mantle volatiles had
escaped into the atmosphere which was then mainly carbon dioxide and water
vapor with some methane, hydrogen sulfide, and inert gases. Free oxygen could
not last long in this environment. The oldest known earth mineral crystals are
zircons of Australia dated to 4.3 billion BP. The seas were forming by 4.2
billion BP. They were acidic and contained massive amounts of iron and other
metals in solution.
The Archean Eon began around 4 billion BP with the beginnings of crustal
formation as the extreme volcanism and incessant meteoric impacts died down.
With much less heat being released from inside the earth, and a young sun
producing about 70% of the energy it does now, global temperatures were
probably down around that existing during the ice ages. It was under these
conditions, in seas containing virtually the same amount of water as now, that
complicated chemicals formed, some of which seeded their own replication, like
chemical crystals. Considering the vastness and variety of nature's laboratory,
it does not surprise me that nucleic acids formed, mixed, and connected,
producing simple mutatable and replicable RNA molecules and eventually all the
life now on earth. What amazes me is that they are the only molecules or type
of molecules to have ever become a basis for life on earth.
By 3.9 billion BP, this molecular soup is thought to have developed
walls, becoming individualized members of the first earth-born living kingdom,
the Monera, which soon left chemical traces and metal concentrations consistent
with those later known to have been produced by bacteria. Asexual reproduction
by fission and a simple form of anaerobic metabolism must also have evolved by
then. By 3.7 billion BP, banded iron formations began to appear which imply an
oxygen generating metabolism in shallow seas as the soluble iron ions combined
with the oxygen and settled out.
The earliest obvious fossils appear in sediments 3.6 billion years old.
These consist of spheroid and ellipsoid single cells and filaments, and
stromatolites. Stromatolites are rock formations produced as a byproduct of
mats of photosynthetic blue-green algae - the Cyanophyta. Though still in
existance today, their heyday ran from 3.5-2.0 billion BP, when they began to
be crowded out by other organisms, including those which metabolized the oxygen
that they had produced.
3.5 billion years ago, the spin of the earth had slowed enough to allow
a nearly 18 hour day, and over a thousand million years of cooling had produced
a surface dotted with numerous small plates separated by ocean basins with,
likely, numerous small subduction areas. Some of these plates had grown enough
in thickness to begin leaving evidence of tectonic activity.
Life continued to evolve, slowly due to the exact duplication of fission
reproduction, but mutations did occur although far less frequently than they do
with sexual reproduction. The early bacteria swarmed over the earth, filling
ecologically supportive niches, and evolving into various types of
single-celled creatures. Most were free-living and left few remains, but by 3.2
billion BP, the colonial stromatolite producing algae had left thick deposits
in what is now North America, Greenland, Africa, and Australia, and probably
existed worldwide within adaptable climates. The carbon dioxide atmosphere was
slowly being reduced to oxygen and carbon, and by 3 billion BP it is thought
that all major metabolic modes had evolved.
Large continents, formed by coalescence of the small plates, were
raising their
Precambrian Shields by 2.8 billion BP.
The Kenoran orogeny (mountain building
episode) occurred from 2.7-2.6 billion
BP as the Superior-Wyoming Province of the
Canadian Shield was raised. This study
is of the area on the southwest edge of the
Canadian Shield. With the raising of
the shields, major stasis was met between the
lithosphere and mantle, and very little
increase in continental area or volume has
occurred since then.
As the Archean Eon drew to a close, the earth enjoyed a short warming
period,
bacterial production of oxygen jumped
up, and the first traces of photosynthetic
bacteria on land were left. 2.5 billion
BP marks the end of the Archean Eon, the
beginning of the Proterozoic Eon, as
well as the beginning of the Middle Precambrian
Era.
The Proterozoic begins in an environment much altered from that existing
at the
beginning of the Archean Eon.
Sedimentation is now the dominant geological process,
contributed to by erosion and
bacteriological processes. Atmospheric oxygen content
climbs seasonally, and the ozone layer,
though still too thin for any protection, has
begun to build. Carbonate reef-like
platforms are now being produced at the other
end of the life cycle. Around 2.4
billion BP, marine acidity has dropped enough to
precipitate iron compounds en masse.
Throughout the world, in submerged areas,
banded iron formations appear and
continue building over the next 600 million years.
Though most has been lost due to
subduction, it has been estimated that they provide
90% of the world's mineable iron
resources.
Glacial deposits were dropped in what is now southern Canada, south
Africa,
and India 2.2 billion years ago, and it
is felt that through most of the Proterozoic,
ice age conditions dominated. Average
worldwide temperatures have typically
been between 12-20 degrees Centigrade
with current levels around 13 degrees.
Most of the earths past since the
Proterozoic has endured temperatures much
warmer, between 18 to 20 degrees. The
primary control here is our distance from
the sun. The state of the gaseous
envelope is secondary. A spike of 2 or 3 degrees
outside the norm has been shown to
induce mass extinctions, but it must be kept
in mind that polar temperatures always
ranged from extreme cold to cool temperate,
and equatorial temperatures always
ranged from extreme hot to temperate.
Prokaryotic (nonnucleated) plankton were abundant 2.2 billion years ago,
when the
atmosphere could first be distinguished
as an oxygen atmosphere, and the ozone layer
began providing a degree of protection.
Large single cells and multicellular
organisms appear around 2.1 billion BP,
and Grypania, a 3/4 inch fossil probably
existed then. Mitochondria, probably
acquired through the symbiosis of purple
eubacteria with early large single cells
or multicellulars, began producing energy
for some aerobic organisms as part of
their genetic lines. Eucaryotes, or nucleated
cells, appear around 2 billion BP,
introducing the second living kingdom - the Proctista.
Early eucaryotes still reproduced by
fission, simply splitting in two.
The Hudsonian orogeny of the Canadian Shield occurred around 1.8 billion
years ago.
This mountain-building episode
initiated the deposition of a new series of sediments
which mark the beginning of the Middle
Proterozoic Period and the Late Precambrian
Period. One group of these sediments,
the Keeweenawan Sequence, built between 1.8
and 1 billion BP, includes about 15,000
meters of lavas, sandstones, and shales. Also,
around 1.8 billion BP, the building of
banded iron formations cease, and red beds of
oxidized iron sediments become common.
300 million years later, another orogeny of
the Canadian Shield occurred, deforming
the Central Province. These Late Precambrian
orogenies probably produced the
Basement Complex granites 1200-1800 feet beneath
the surface of northeast Oklahoma.
Ozarkcollenia, a stromatolyte producer, lived on volcanic tuffs in what
is now the
Missouri Ozarks 1.5 billion years ago.
Mitosis and meiosis and the Plant and Animal
Kingdoms were beginning to evolve, with
their associates of sex, gender, and
individual lifespans. Sponge spicules
have been reported from deposits of that age.
Terrestrial soil microbes appear well
extablished by 1.4 billion BP, and by 1.2
billion BP, evolution had produced a
wide variety of monera, plankton, seaweeds,
and numerous moranids.
One billion BP marks the beginning of the Upper Proterozoic Period.
Rodinia now
exists, formed by the unification of
Laurentia and Gondwanaland, the Grenville orogeny
is underway, and North America is
attached to Antarctica. 900 million years ago, tiny
animals, worms, sponges, and huge
probable algal organisms existed. From 800 to
around 650 million BP, it appears as
though ice encircled the equator, possibly
because the earth's axis tilted further
than normal. The mesoderm and coelom
evolved back then, and 750 million
years ago Rodinia split into Laurasia and
Gondwanaland.
675 million BP marks the end of the Proterozoic Eon, the beginning of
the
Phanerozoic Eon which is still ongoing,
and the beginning of the Ediacaran Period. At
this time, North America appears to
have sat on the equator with South America on
its northeast side, Antarctica on its
southeast side, and Australia on its southwest
side. Following the Late Proterozoic
ice ages, global temperatures appear to have risen
high enough to prevent ice formation
even at the poles.
Faunal assemblages from the Ediacaran Period have been located and
described from
the Canadian Rockies, southwest Africa,
Newfoundland, England, North Carolina,
northern Siberia, the Baikals, and
Australia. Remains from this period indicate the
evolution of jellyfish, corals,
conulariids, and other probable coelenterates
unaffiliated to more recent fossil
forms; worms, very primitive trilobites, and
branchiopods, among many forms not yet
placed on the familiar phyletic tree. Of
currently existing animal phyla, the
Porifera, Annelida, Arthropoda, and Coelenterata
appear well represented. All Ediacaran
fauna were low-energy, passive creatures.
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