#Sea Levels?
5 messages in this thread
>Glomar Challenger brought some unusual core samples from drillings of
sea/ocean floors: anhydrites from the Mediterranean and the Gulf of Mexico,
Miocene age ( 6 mya) evaporite deposits in the Mediterranean basin were left
when sea level fell below the Straits of Gibraltar. In addition, there exists
a circulation loop through the strait. Due to evaporation, the Med is more
saline than Atlantic sea water. As evaporation continues, gypsum becomes an
evaporite precipitate to the Med floor. Also the brine becomes denser and
sinks toward the bottom flowing out the Strait of Gibraltar. Less dense
seawater flows east through the Straits into the Med. Ref: Earth, 4th Ed.
W.H.Freeman, pp328-329. A similar mechanism could be proposed for the Gulf of
Mexico, but I have no suporting evidence. I believe that the geology of the
Gulf is still somewhat problematic.
> Publication by Columbia U
Please direct me to this one specifically, can't comment much without further
info
The Atlantic ridge represents the original rift region between N.America and
Europe/Africa, erosional sediments would be expected on the new basaltic floor
as the proto-Atlantic developed.
>Terrestrial-type sedimentary rocks with apparent glacial striations
There exists enough evidence of ice-rafting of glacial boulders to satisfy me
on this one.
> Limestone found when drilling in the Maraianas Basin
The only reference to limestone in deep sea formations that I have is John
McPhee's Assembling California. Ophiolitic suites of rocks may include
limestone in the upper sequences. Island arc subduction or accretion are
possible sources of seeming shallow water deposits now located in deep sea
trenches.
> River (V-shaped) canyons, running down the height of the continental shelves
Turbidity currents are the proposed hypothesis for the formation of strongly
eroded submarine canyons. Slumping of continental shelf deposits down the
continental slope results in suspension of the solids in the water. This
denser body of water, compelled by gravity, rushes downslope exercising a
strong cutting action as it flows. The resulting abyssal sediments are graded
beds of sand silt and clay. Ref: Earth, 4th ed, pp. 282-285
>A discussion of how such a hypothesis would still permit the isolation of
Australia.
No comment
>Sunken flat-topped sea mounts at a wide variety of depths.
The leading hypothesis for the presence of guyots or flat-topped seamounts is
that they represent the subsided remains of volcanic mountains, once raised
above sea level and then eroded flat by wave action. Because the sea volcanoes
grew from a hot spot in the mantle, once the oceanic plate moved away from the
hot-spot, the eruptive rock and its basement crust cooled and then sank to
below sea level. Ref: Earth, 4th ed, pp288-289
> Legends of floods worldwide
No comment
Regards – Michael
Dear Michael,
Many thanks for your impressive posting. What you say about sea mounts is just
what I saw, it sounds very sensible, as do your comments on the Mediterranean.
As usual in these books no proper references are quoted, I'll have to track
down the Columbia U publications. I get the impression that (unlike some
people) this man doesn't actually invent evidence, he just gets muddled.
Two things bother me, though. I'd have thought that IF there are erosional
deposits on the mid-Atlantic ridge, these could not readily be explained by
their being remains of the original coastline as the continents parted? Is not
the Ridge all new(ish!), could it have carried coastal deposits as it spread?
Having looked at drawings of the floor of the Atlantic, with a canyon running
from Gibraltar nearly to the ridge (though this might not be V-shaped), at the
sonar cross-sections of the *stepped*, V-shaped canyons, some of which are
filled, and at the 'delta' at the 'mouth' of the Congo canyon, I am, in my
admitted ignorance, uncomfortable with the mudslide hypothesis. Could I ask if
you – obviously an expert – are entirely comfortable with it? Or is it that
the obvious absurdity of any 'dry' hypothesis compels you to suggest it?
Many thanks for the help, and for the references, which I shall follow up.
Chris
I agree that *if* fluvial sediments were found at the ridge itself, then
continental sources are very unlikely. I'd need to see the Columbia U data.
I don't have as detailed a map of the Congo canyon as you, so I can't respond
directly to the point you have raised. However, given my experience observing
the cutting power of streams heavily laden with sediment, turbidity currents do
go a long way toward explaining such features. since the Grand Canyon
represents erosional processes in large part due to accelerated cutting action
of heavy stream loading since the Miocene (15-20 mya ), I can accept similar
continental shelf formations where rivers exist. Which raises an interesting
point. Are there similar features on the continental margins where no evidence
of past rivers exists?
While I mentioned mudslides as a source of turbidity currents, the mechanism
doesn't distinguish between mud resuspended in a slide, or mud suspended in
stream flow.
****I am not an expert*****
I am, like you, intrigued, puzzled and fascinated by such features, anomalies
and engimas that you listed in the first post. In search of answers and
understanding, I have compiled a decent library that is I guess Natural History
in scope. Geology is a significant part of that. A very interesting book you
might enjoy is UNKNOWN EARTH: A handbook of Geological Enigmas, by William
Corliss, published by The Sourcebook Project, PO Box 107, Glen Arm, MD 21057.
ISBN 0-915554-06-2
Regards – Michael
That's an enormously helpful response, as have been the others, thank you, ALL.
Though I still feel that the raw data is always better than an interpretation
by anybody. The advantage of 'enigma' books is that – if properly referenced –
they save time when trying to find the original sources. That little lot
should help loads. Chris
ex
Thats is the plate tectonic theory on how Hawaii got here or there, they say
its moves throughout time.