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 meteorite-l...@meteoritecentral.com 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 rmfor...@comcast.net 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 _______________________________________________
