ground views of over 100 .1-.5 km shallow (ice comet fragment bursts) craters, Bajada del Diablo, Argentina (.78-.13 Ma BP) [42.87 S 67.47 W] Rogelio D Acevedo et al, Geomorphology 2009 Sept: Rich Murray 2010.03.28

[Rich Murray]

ground views of over 100 .1-.5 km shallow (ice comet fragment bursts)
craters, Bajada del Diablo, Argentina (.78-.13 Ma BP) [42.87 S 67.47 W]
Rogelio D Acevedo et al, Geomorphology 2009 Sept: Rich Murray 2010.03.28

http://rmforall.blogspot.com/2010_03_01_archive.htm

Saturday, March 27, 2010

http://groups.yahoo.com/group/astrodeep/message/47
_______________________________________________


It's a pleasure to find and share many high quality photos on
the ground, easy to find via Google Images.

They look much like what I find in all directions for 200 km
from my home in Santa Fe, New Mexico, as well as seen in
views given by Dennis Cox, California, and Pierson Barretto,
Brazil, as well as by Tim McElvain and Michael E. Davias.

[ you may have to copy and paste these URLs into your
browser ]

http://www.espacial.org/images/jpg2/bajada_diablo.jpg

27 x 15 km crater field, 0.3 to 1.0 km diameter
42 45 S  67 30 W [ 42.75 S 67.5 W ]
about .2 km resolution

500x390 63K jpg

Maximiliano C L Rocca
Rocca M. C. L. (2006). Two New Potential Meteorite
Impact Sites in Chubut Province, Argentina.
Publicado en inglés en Meteoritics and Planetary Science
(MAPS) Vol. 41 (8), Supplement, p.A152, 2006.
Trabajo presentado en el 69th Annual Meeting de la
Meteoritical Society, Zurich, Suiza, Agosto 2006.

http://www.national-geographic.cz/assets/veda-a-vesmir/obr1_bajada_del_diablo.jpg

man in large shallow dark crater
512x367 53K jpg

http://d.yimg.com/i/ng/ne/afp/20090908/19/741448635-campo-crateres-argentina-abre-puerta-investigaciones-cientificas.jpg

man in large shallow dark crater
437 x 313 - 25k - jpg

http://blogs.nationalgeographic.com/blogs/blogwild/2009/09/mega-meteorite-mystery.html

3 images -- within the blog article, right click each photo to
Save, or select, Open in a new window, to access larger
views, which can also be right clicked to Save

two men, dark green and dark red pants, by far edge of flat
center of crater, with broken dark rocks, up to 2 m size,
with higher crater rim of lighter rocks
608 x 456 - 139k - jpg

full screen view of Rogelio Acevedo [ dark green pants ]
at top rim edge of large crater, with dark flat center behind
and below him, then the less high opposite crater rim of
lighter color rock, curving around behind him on the right side
of the view, with view across plain to far mountains [ south ? ]
-- at his feet the rocks are about .3 to 2 m size
and "volcanic", blue-black mixed with red

very large full screen view of man with red pants with metal
detector at edge of flat crater center of dark gravel-like
pebbles, this side of the crater rim with a variety of sizes and
types of "volcanic" dark, red, grey, and white rocks, mixed
jagged and rounded

September 11, 2009 4:22 PM
Megameteorite Mystery
Posted by Amy Bucci -- Blogwild Contributor

National Geographic staffer Fabio Amador shared some news
about one of our National Geographic Society/Waitt grantees,
Rogelio Acevedo, a geologist from the Centro Austral de
Investiggaciones Cientificas in Argentina. [ in green pants ].

In a remote region of Patagonia, enormous craters measuring
up to 500 meters wide and 50 meters in depth could be
evidence to a bombardment of meteorites.
This meteoroid impact field, the largest in the southern
hemisphere, is of extreme interest for Dr. Acevedo.
This site, call Bajada del Diablo or Devil's Descent, contains
more than one hundred impact craters spread over 400
square kilometers.

Curiously, no meteorites have ever been found, but Acevedo
and his team will be traveling there this October in hopes to
solve the mystery by studying petrographic and mineralogic
marks on the rocks.
We'll be sure to update everyone when the team returns!

www.lanacion.com.ar/anexos/fotos/32/1050232.jpg

444x269 44K jpg

Below is the same image (scroll down) at:

www.tomamateyavivate.com.ar/2009/08/

distance view in an article of large shallow light grey and tan
crater past foreground slope with bushes
_______________________________________________


[ writen 2009.11.13 ]

My goal as a conscientious geology amateur is to stimulate
exploration of remarkable research opportunities by freely
providing convenient information and my own observations,
creative conjectures, and visions.


http://www.google.com/hostednews/afp/article/ALeqM5hRa6u8O0ZprE7dF10g8FMNv1ERig

Patagonia site of world's biggest crater field: study

(AFP) - (AFP) - Sep 8, 2009 - 19 hours ago

BUENOS AIRES -- Argentina can lay claim to the world's
largest crater field, a volcanic area in Patagonia known as the
"Devil's Slope," according to a study released Tuesday.

With  400 square kilometers (154 square miles), the over
100 shallow craters are 100-500 m wide, 30-50 m deep.

On Sept 9, 2009,

Jason Utas posted, "...There are quite literally hundreds
(if not thousands) of elongate depressions that are quite easily
visible from the air... literally thousands of square kilometers...

Darren Garrison agreed, "...Sounds a lot like
Carolina Bays to me."

http://www.meteoritecentral.com

[hidden email]

http://six.pairlist.net/mailman/listinfo/meteorite-list

I spent the day, first finding the abstract, and then scanning
north from their location with Google Earth,
finding many similar features, and many more since,
which I will list at the end of this report.

Acevedo, Rogelio D. a,  J. F. Ponce a,
Maximimiano C. L. Rocca b, J. Rabassa a,c, and
 H. Corbella d,e 2009 Sept.
Bajada del Diablo impact crater-strewn field:
The largest crater field in the Southern Hemisphere.
Geomorphology. 110(3-4): 58-67.
a CADIC-CONICET, c/B.Houssay n°200, 9410 Ushuaia,
Tierra del Fuego, Argentina
b Mendoza 2779, 1428DKU Buenos Aires, Argentina
c Universidad Nacional de la Patagonia-San Juan Bosco,
Sede Ushuaia, Argentina
d CONICET and Museo Argentino de Ciencias Naturales
"Bernardino Rivadavia," Buenos Aires, Argentina
e Universidad Nacional de la Patagonia Austral,
Río Gallegos, Argentina
Received 25 September 2008;
revised 26 March 2009;
accepted 29 March 2009.
Available online 14 April 2009.

http://dx.doi.org/10.1016/j.geomorph.2009.03.026

[ summary from report ]

Bajada del Diablo field described by H.C. in 1987,
though its origin not firmly established.

over100 almost circular, crater-type structures with diameters
ranging from 100 to 500 m in width and 30 to 50 m in depth.
three separated impact crater fields, formed simultaneously
on a Miocene basaltic plateau and Pleistocene pediments,
later eroded by Late Pleistocene fluvial processes,
thus three major separate areas.

Our work concentrated on one of these impact craters fields,
on the Filu-Có plateau, NE from the other two.
The craters do not present a classic elliptical distribution.
The studied area (60 km2) [ Area 1 -42.80 -67.47 ]
is composed of
(1) a volcanic plateau of late Miocene basalts and
trachybasalts of the Quiñelaf Volcanic Complex,
(2) coarsely stratified sedimentary breccias, conglomerates
and sands of a contiguous Pleistocene pediment
which extends around most of it,
and (3) late Pleistocene-Holocene fluvial deposits
forming terraces and network channels.
The larger area has at least 69 impact craters found both on
the Miocene plateau and the Pleistocene pediment,
but absent on the Late Pleistocene-Holocene fluvial landforms.
[ Exact locations in the report ]

Crater structures are similar in both target rocks,
although showing different behavior in relation to rock type.
They are simple rings, bowl-shaped with raised rimrock.
Basaltic boulders have been deposited as a ring-shaped pile
and the ejecta are found towards the NE flanks.

The craters present a hummocky bottom, with dry ponds
and lakes in the center, but they do not show raised central
peaks.
The rocks within the craters have strong, stable magnetic
signature.
No meteorite fragments or other diagnostic landmarks are
found.

The craters have been partially filled-in by debris flows
from the rim and wind-blown sands in recent times.
The origin of these crater fields may be related to multiple
fragmentation of one asteroid which broke up before impact,
perhaps traveling across the space as a rubble pile.
When entering the Earth atmosphere, the impacting
fragments were at an estimated shallow input angle
between 15º to 25º from the horizontal.

Alternatively, multiple collisions of comet fragments could
explain the formation of these crater fields.
The layout of the ejecta that moves preferably in the
downrange direction indicates a high velocity impactor
coming from SW towards NE.
Based on field geological and geomorphological data,
the age of this event is estimated to be from the
late Pliocene-early Pleistocene and the late Pleistocene,
most likely early-middle Pleistocene (i.e., 0.78-0.13 Ma ago).

Their paper is detailed, with 2 geological maps, Fig. 1 and 2.
The altitude is about 500 m.

Area 1 -42.80 -67.42
Area 2 -42.85 -67.72
Area 3 -42.97 -67.71.

Fieldwork was in May, 2007, on about 90 km**2
between 42 44 to 42 51 S and 67 36 to 67 24 W,
27X15 km,
with over 100 craters 60 to 350 m in width, 30 - 50 m deep,
in 3 areas, with an original total impact area before erosion
398 km**2, and possibly 200-300 original craters.

Area 1: 80 km**2 , 66 craters,  0.825 craters/km**2
Area 2: 32, 12, 0.37
Area 3: 44, 15, 0.34
average crater density 0.6
Area 1 was studied with aerial photos,
and fieldwork on 10 craters.
Areas 2 and 3 were counted only by satellite images of
low resolution.
There may be a possible fourth area S and SW of Area 1.

Area 1 on the Filu-Co Plateau had
1. volcanic pleteau of Late Miocene basalts and trachybasalts
of the Quinealaf Volcanic Complex
 2. coarsely stratified sedimentary breccias, conglomerates,
and sands of the Pampa Sastre Fm., a Late Pliocene-Early
Pleistocene pediment which extends around most of it, and
3. Late Pleistocene fluvial deposits forming terraces and
network channels.

The central dots seen from above on most of the 66 craters
are dry lake surfaces.

For the 18 craters found on top of the Miocene basaltic
plateaus (volcanic mesas), including craters A, B, C, G
in the oblique 3D view in Fig. 5, no meteorite fragments
or other megascopic diagnostic landmarks have been
found among the boulders and pebbles of vesicular basalt.
Chemical tests found some Ni in the bottom sands and silts
of two horseshoe-shaped craters A and A', while X-ray
diffraction found magnetite and petrogenic silicates, and
maybe taenite, a rare Fe-Ni mineral.

Craters on the pediment surface have hummocky
bottoms with dry ponds and salt lakes in the centers,
and were later dried and filled up with gravel and
sand,  from debris flows from the rim and wind-blown
sands, and so are often hard to see.
Ejecta is often strongly marked in views from above.

The entire crater field seems not elliptical, but chaotic.
The lack of meteoritic fragments suggests vaporization
of the object from very high temperatures during a
hypervelocity impact.
A rubble-pile would fragment greatly in the air
before ground impact.

Possibly, and more likely, a small comet nucleus,
several hundred meters in diameter, formed by water and
carbon dioxide ice,  with a small fraction of rocky matter,
generally very fragile, would also fragment
into hundreds of pieces in the air before ground impact,
leaving no physical traces behind.
(H. Campins and Y. Fernandez, 2002,
M.C. Festou et al., 2004).

The vaporization from impact makes a nearly spherical
expanding envelope of hot gas, creating fairly round craters.

Research was funded by CONICET and The Planetary
Society, Pasadena, California.  Dr. William McDonald,
State University of NY at Binghamton, visited Ushuaia.
[ end of summary ]

Their Table 2 lists 66 craters in Area 1 on Filu-Co plateau.
Letters indicate those with fieldwork, and numbers those
measured on aerial photos.

I list some here with decimal degrees, and widths,
lowest crater depth, and highest ejecta or terrain in km.
Google Earth and Maps has about the same quality and
resolution as their photos, about 1 m, enough to see
2 ruts in a dirt road, but not enough to tell a car from
a  bush, boulder, or hole.

The first 6 are on grey basalts and trachybasalts.

C -42.788574 -67.548570 .860 km deep, .894 N ejecta,
W edge eroded [ Fig. 4, 5 ]

D -42.785062 -67.533669 .278, .850, .873,
S edge eroded [ both Fig. 4]
D'  -42.782352 -67.535068 .219, .868, .875

G -42799292 --67.526446 .291, .779, .804,
S edge eroded [ Fig. 4, 5 ]

H -42.770845 -67.538997 .168, .917, .923

The next 5 are on sandstones and conglomerates.

A -42.808171 -67.436316 .220, .648, .653
[ on the right (E) in Fig. 4, 5 ]

A' -42.807212 -67.441747 .165, .654, .656
[ on the left (W) in Fig. 4, 5 ]

B -42.805004 -67.505493 .351, .683, .707
[ both Fig. 4, 5 ]
B' -42.809174 -67.503760 .271, .681, .683

E -42.791507 -67.489361 .355, .681, .687

Google Earth does show color in this bleak badlands.
Processing the color data may be helpful.

>From here on, I will be commenting as I explore.

Here are the Windows/Linux keyboard commands that make
it easy to "fly" easily, creating an intuitive 3D grasp
of the landscape -- my laptop runs at 1 GHZ with a graphics
card, Windows Vista, Firefox, and 3 GB RAM:

Full screen mode: F11
Lat/Long grid: Ctrl L
Slow movement down: add Alt before other keys
Zoom in, out: PgUp, PgDn keys
Move left, right, forward, back: arrow keys
Tilt view up, down: Shift down arrow, up arrow
Rotate view in circle clockwise, counterclockwise:
Shift right arrow, left arrow
Tilt up towards horizon, down towards directly below:
Shift down arrow, up arrow
Stop, start movement: space bar
Look in any direction: Ctrl, left mouse button and drag
New placemark: Ctrl Shift P
To delete or rewrite a placemark title,
right click it and select Properties.
Reset view to north as forward:  n
Reset tilt to top-down view: u
Select Tools to select Web to return to your other screens.

It's easy to look down about 45 degrees while moving straight
ahead in any direction at an eye elevation of 1-200 km,
scanning a straight strip half-way around the world,
stopping to placemark, examine, and measure any features.

r1 -42.768 -67.484 green pond .5 km, .695 high
on eroded slope 2 km E of H, 3 NNW of E,
while 6.84 km NNE is

r2 -42.708 -67.484 dry white eroded lake 1.4X.6,
.497 high, slopes WE .545-.500

Erosion, possibly immediate catastrophic regional floods,
similar to glacial volcanic debris flows, mudflows,
outburst floods, and lahars, can follow and alter craters and
impact shocked bedrock, concentrating minerals,
and evolving oriented lakes and features.

Could much of this be from the 12,950 BP Younger Dryas
start?

Could the white minerals, common in various depressions
on high durable surfaces, derive largely from the impactors?

R3 -42.729681 -67.686537 lake 1.11X.46, 1.082, 1.095
Quinelaf Eruptive Complex. Final basic lavas facies [Fig. 2]

p 60 4.1 Quinelaf eruptive complex
"...On the basis of several radiometric datings,
Ardolino (1981) identified that the latest volcanic activity of
this trachytic unit (the Final Lava Facies) took place in the
Miocene."

R4 -42.143501 -67.686537 lake 1.16X.60, 1.486, 1.542,
cluster

R5 -41.474665 -67.912145 3.0 round,
flat shallow 1.3 white core, .968, 1.167 area el 1 km N
also crater 1.2X.6 on SW rim, 5 km E of Rd 8 ns,
28 km N of Rds 5 and 7.
1X.5 green [farm?] on NW rim of white core, with road.
Part of a regional crater field on a dark, incised plateau --
the edges of the plateau are dark layers .1 km deep at least.
This area is 130 km N of the Bajada del Diablo impact crater
field.
_______________________________________________


Dennis Cox, amateur extraordinaire, with 6 views given via
Google Earth by Rich Murray of 360 m high mountain E of
Fresno, CA, with uphill and then downhill ejecta melt flows
-- informative book with 92 color images: 2010.03.25

http://rmforall.blogspot.com/2010_03_01_archive.htm

Thursday, March 25, 2010

http://groups.yahoo.com/group/astrodeep/message/45


http://craterhunter.wordpress.com/the-planetary-scaring-of-the-younger-dryas-impact-event/the-benivides-impact-structure/

Dennis Cox, Fresno, California

http://cosmictusk.com/

George Howard, Raleigh, North Carolina

http://sites.google.com/site/cosmopier/

Pierson Barretto, Brazil

http://www.impactstructure.net/working-hypothesis.html

Thornton H. "Tim" McElvain, Santa Fe, New Mexico

http://www.perigeezero.org/treatise/YDB/ObliqueImpacts/index.html

Michael E. Davias

Rich Murray, MA
Boston University Graduate School 1967 psychology,
BS MIT 1964, history and physics,
1943 Otowi Road, Santa Fe, New Mexico 87505
505-501-2298  [hidden email]

http://groups.yahoo.com/group/AstroDeep/messages

http://RMForAll.blogspot.com new primary archive

http://groups.yahoo.com/group/aspartameNM/messages

group with 142 members, 1,588 posts in a public archive

http://groups.yahoo.com/group/rmforall/messages

participant, Santa Fe Complex www.sfcomplex.org
_______________________________________________









============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org