Erosional unconformity (or crossbedding) in Endurance?

Curious what the group makes of this recent (Sol 288) image from
Opportunity:

http://marsrovers.jpl.nasa.gov/galle...P2543R1M1.HTML

(If you have the bandwidth, by all means go for the full image, the
following is much clearer there).

Two things of note: First, the inclined layers that form the nearly
buried base of Burn's Cliff are very interesting in an dof themselves.
It looks (to my very untrained eye) like an erosional unconformity of
some type (the unconformity itself is clearly visible in places). I've
got trouble figuring out how to get that in the first place. But
looking at the tilited layers themselves, it appears as if there might
be some other subtle unconformities.
What's going on? Underwater deposition on a slope, followed by
(wave?) erosion and redeposition? I've got real trouble believing a
long timeframe explaination for this (like deposition -- upheaval &
erosion -- 2nd period of deposition).
Secondly, the small peaked rock in the midground shows some
wonderful layer-cake structure, more distinct than any other small
rock or outcrop I've seen. Presumably this fell down from upper
layers, but when did the erosion that highlighted the layers occur?
After weathering out of the upper strata seems most likely to me, but
it could I suppose be coincidence of how it landed (weathered "point"
upright).

--
Brian Davis

"Erosional unconformity". Sounds like a tautology to me.
cheers
Bill

On 18 Nov 2004 04:41:11 -0800, (Brian Davis) wrote:

What's going on? Underwater deposition on a slope, followed by
(wave?) erosion and redeposition? I've got real trouble believing a
long timeframe explaination for this (like deposition -- upheaval &
erosion -- 2nd period of deposition).
Secondly, the small peaked rock in the midground shows some
wonderful layer-cake structure, more distinct than any other small
rock or outcrop I've seen. Presumably this fell down from upper
layers, but when did the erosion that highlighted the layers occur?
After weathering out of the upper strata seems most likely to me, but
it could I suppose be coincidence of how it landed (weathered "point"
upright).


Infilled craters?

On Sun, 21 Nov 2004 09:32:15 +1100, "Landy" wrote:

"Erosional unconformity". Sounds like a tautology to me.
cheers
Bill

Why?

"vonroach" wrote in message
...
On Sun, 21 Nov 2004 09:32:15 +1100, "Landy" wrote:

"Erosional unconformity". Sounds like a tautology to me.
cheers
Bill

Why?
An unconformity by definition is an erosional surface. All you needed was
"unconformity".
cheers
Bill

"Landy" wrote:

:
:"vonroach" wrote in message
.. .
: On Sun, 21 Nov 2004 09:32:15 +1100, "Landy" wrote:
:
:"Erosional unconformity". Sounds like a tautology to me.
:cheers
:Bill
:
: Why?
:An unconformity by definition is an erosional surface. All you needed was
:"unconformity".

That's not a tautology. A tautology is a
statement. "An unconformity is erosional" is a tautology.

Tautology is not an antonym of oxymoron.

:cheers
:Bill
:

--
Real men don't need macho posturing to bolster their egos.

George W. Harris For actual email address, replace each 'u' with an 'i'.

"George W. Harris" wrote in message
...
"Landy" wrote:

:
:"vonroach" wrote in message
.. .
: On Sun, 21 Nov 2004 09:32:15 +1100, "Landy" wrote:
:
:"Erosional unconformity". Sounds like a tautology to me.
:cheers
:Bill
:
: Why?
:An unconformity by definition is an erosional surface. All you needed
was
:"unconformity".

That's not a tautology. A tautology is a
statement. "An unconformity is erosional" is a tautology.
That's not what it says in my dictionary. A tautology is a repetion of
ideas that do not impart any more information to the reader, that appear in
the same clause, e.g. erosional unconformity. The title of the email in
this case - call it a tautological expression if you want to be pedantic.
An oxymoron on the other hand is a clause which contradicts itself. A
"non-erosional unconformity" would be an example of this - although I've
never heard anyone use that expression.
cheers
Bill

Landy a écrit dans le message ...

"George W. Harris" wrote in message
.. .
"Landy" wrote:

:
:"vonroach" wrote in message
.. .
: On Sun, 21 Nov 2004 09:32:15 +1100, "Landy" wrote:
:
:"Erosional unconformity". Sounds like a tautology to me.
:cheers
:Bill
:
: Why?
:An unconformity by definition is an erosional surface. All you needed
was
:"unconformity".

That's not a tautology. A tautology is a
statement. "An unconformity is erosional" is a tautology.
That's not what it says in my dictionary. A tautology is a repetion of
ideas that do not impart any more information to the reader, that appear in
the same clause, e.g. erosional unconformity. The title of the email in
this case - call it a tautological expression if you want to be pedantic.
An oxymoron on the other hand is a clause which contradicts itself. A
"non-erosional unconformity" would be an example of this - although I've
never heard anyone use that expression.
cheers
Bill



An erosional unconformity is an unconformity caused by
erosion. An angular unconformity may be eroded but is likely not caused by
erosion. A disconformity is an "unconformity marked by
appreciable erosional relief." 1:
I do not know however how one would equate an erosional
unconformity with crossbedding!! That would be an apple-
orange situation.
A tautonym is a repeated name such as a "linaria linaria
karst" 1:


JOL

1: Dictionary of Geological Terms AGI

"maison.mousse" wrote in message
...

Landy a écrit dans le message ...

"George W. Harris" wrote in message
. ..
"Landy" wrote:

:
:"vonroach" wrote in message
.. .
: On Sun, 21 Nov 2004 09:32:15 +1100, "Landy" wrote:
:
:"Erosional unconformity". Sounds like a tautology to me.
:cheers
:Bill
:
: Why?
:An unconformity by definition is an erosional surface. All you needed
was
:"unconformity".

That's not a tautology. A tautology is a
statement. "An unconformity is erosional" is a tautology.
That's not what it says in my dictionary. A tautology is a repetion of
ideas that do not impart any more information to the reader, that appear
in
the same clause, e.g. erosional unconformity. The title of the email in
this case - call it a tautological expression if you want to be pedantic.
An oxymoron on the other hand is a clause which contradicts itself. A
"non-erosional unconformity" would be an example of this - although I've
never heard anyone use that expression.
cheers
Bill



An erosional unconformity is an unconformity caused by
erosion. An angular unconformity may be eroded but is likely not caused
by
erosion. A disconformity is an "unconformity marked by
appreciable erosional relief." 1:
I do not know however how one would equate an erosional
unconformity with crossbedding!! That would be an apple-
orange situation.
A tautonym is a repeated name such as a "linaria linaria
karst" 1:
Erosion is still a fundamental part of all unconformities, and in my book it
causes them - if you don't have erosion, you don't have an unconformity.
The differences between different types of unconformities leads to the
question of what causes the erosion to happen - passive uplift, folding,
eustatic sea level changes etc. Erosion is still the primary cause. I have
never seen the term "erosional unconformity" used - the types in my textbook
are angular unconformity, nonconformity and disconformity.
cheers
Bill

"Landy" wrote in message ...

The differences between different types of unconformities leads to the
question of what causes the erosion to happen - passive uplift, folding,
eustatic sea level changes etc.

Uhh-OoOh! (Is somebody talking to me? After all this time?)


Erosion is still the primary cause. I have
never seen the term "erosional unconformity" used - the types in my textbook
are angular unconformity, nonconformity and disconformity.
cheers
Bill

CORR-bloody RRECT! !! Get RIGHT UPPEM, Bill. And left too,
while you're at it. Keep it NON-GENETIC!