Mathematics – Logic
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p53c1525h&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P53C-1525
Mathematics
Logic
[3617] Mineralogy And Petrology / Alteration And Weathering Processes, [5420] Planetary Sciences: Solid Surface Planets / Impact Phenomena, Cratering, [8404] Volcanology / Volcanoclastic Deposits, [8485] Volcanology / Remote Sensing Of Volcanoes
Scientific paper
A ~1-km-diameter circular depression was discovered near Samangan, Afghanistan (68° E, 36° N), while processing and interpreting ASTER and Google Earth™ (Quickbird) imagery in support of USGS mineral resource assessment activities in Afghanistan. This feature is ~169 m deep based on the average elevation of the rim (1,972 masl) to the lowest point on the floor of the depression (1,803 masl). The surrounding and host bedrock is comprised of a sequence of Paleocene (?) and Late Cretaceous rocks dominated by rudist limestone, marl, and dolomite with minor amounts of interbedded clastic and volcaniclastic rocks. Approximately 150 km to the SW of this feature, recent volcanic activity in the form of Pliocene-Quaternary age alkali basalt, ranges in composition from trachybasalts to leucite basanite, and overlays this same carbonate rock sequence along the Sarlog River in Bamyan Province. Middle Miocene red clay and siltstone bedrock is also exposed nearby to this depression along the incised Samangan River valley. Massive Jurassic halite evaporates, which are present in the subsurface ~ 70 km north of the depression (possible source materials for salt diapirism), are absent in coeval outcrops ~70 km south of the depression. Initial photogeologic interpretation suggests that this feature resembles an impact crater, although it is coincident with both a major NW trending fault lineament and a nearby known natural gas occurrence named “Durannsav”. Also, this feature is also accompanied by a fluvially dissected, SE trending, 6.6 km^2 sheet of unconsolidated sediment that resembles an ejecta blanket on the southeastern flank of the crater. This ejecta material is lithologically distinct from the surrounding and host carbonate bedrock material, based on spectral analysis of ASTER imagery spanning the VNIR-SWIR (0.56 - 2.40 μm) and TIR (8.29 - 11.32 μm) wavelengths. For example, ASTER spectral analysis and mineral mapping suggest that the host bedrock is dominated by calcite and clay mixtures, perhaps due to the weathering of carbonate rocks containing high insoluble residue contents. In contrast, the ejecta material appears to contain mixtures of carbonate and intermediate- (feldspar-bearing) to mafic-volcanic rocks which are dominated by more abundant clay minerals identified as smectite and illite. The latter ejecta material also exhibits weak to absent carbonate spectral absorption features as compared to host bedrock areas, and is characterized by downstream flow deposits which resemble those emplaced by wet pyroclastic surges transforming into lahars. This crater also lacks evidence of overturned bedding structures, which is typical of impact craters such as Meteor Crater, AZ. Based on existing remote sensing evidence presented above, we interpret this feature to be of diatreme origin and perhaps related to the same Pliocene-Quaternary volcanic activity preserved along the Sarlog River valley. We will present further evidence of this through comparative spectral and geomorphological analysis of remote sensing datasets covering field accessible analog features in the Southwest United States.
Hubbard Bernard E.
Sanfilipo J. R.
No associations
LandOfFree
An unusual circular depression in Samangan province, northern Afghanistan: impact crater, diatreme, salt diapirism or karst related? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with An unusual circular depression in Samangan province, northern Afghanistan: impact crater, diatreme, salt diapirism or karst related?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and An unusual circular depression in Samangan province, northern Afghanistan: impact crater, diatreme, salt diapirism or karst related? will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1499260