The Sierra Madera crater is listed in the PASSC database, hosted at Canada's University of New Brunswick, as a 13 km structure exposed at the surface in sedimentary target rock. The database also notes that the structure is 100 million years old or less (Cretaceous). The structure is located in west Texas' Pecos County, and is primarily located on private ranch land, but is crossed by Texas Hwy 385.
Evidence of Impact Origin
The impact origin of each location listed on this website has been supported by unambiguous diagnostic evidence of hypervelocity impact that has been reported in a scientific (usually peer reviewed) context. Without such evidence, a geological structure is not a confirmed impact crater. This section, which is included for each crater on this website, is not an exhaustive list of such published evidence, but is meant to demonstrate that appropriate work has been done for each listing.
Wilshire, H. G., Howard, K.A. and Offield,T.W., Impact breccias in carbonate rocks, Sierra Madera, Texas. Geological Society of America Bulletin, v. 82, pp. 1009-1018. 1971.
Howard, K. A. and Offield, T. W. Shatter Cones at Sierra Madera, Texas. Science, 1968: 162(3850), 261-265.
Nature of diagnostic evidence:
Other significant evidence: breccia, megabreccia, morphology.
A Visit to Sierra Madera Impact Crater
Approaching the crater from the north, from Fort Stockton, the visitor drives over a couple of ridges that, more-or-less, mark the original crater perimeter, before dropping down into the shallow annular basin, literally meaning ring-shaped basin, which surrounds the central uplift, or rebound peaks, at the center of the impact. The scale is immense. From the remnant crater rim, the central uplift looks like a small mountain range, and the far horizon marks the opposite rim of the crater. Even having visited several prior large meteorite impact craters, both I and my travelling companion were somewhat awed.
The range of hills representing the central uplift of the Sierra Madera impact crater is visible from Interstate 10, in Fort Stockton, 21 miles to the north, and is virtually impossible to miss as you approach the crater on Hwy 385. There are also clear road signs marking the rims of the impact crater, coming from both north and south. Looking across the crater region from the raised north rim, as in the picture above, one sees a subtle expression of the annular (or ring shaped) basin surrounding the uplifted central rebound peaks.
Hwy 385 nearly bisects the crater from north to south, passing through the annular basin and just to the west of the central uplift. Though the crater is severely eroded, many of the cobbles along the side of the road are comprised of limestone breccia. A few outcrops near the center seem to be a fluvial or alluvial conglomerate, perhaps post-dating the crater. The surrounding land is private property, and trespassing is not allowed. The shoulders of the highway are wide, however, and we found plenty of room to safely pull off. As with nearly every other highway shoulder in the country, highway debris, old fencing remnants, and so forth, make flat tires a reason for modest caution. Rattlesnakes are also abundant in this area, and a large feral boar crossed the road not far from me while I was shooting pictures. Stay aware.
This part of west Texas is a vast, very flat, open plain, and the area is very quite and peaceful, lending itself to contemplation and the study of rocks. There is very little else around.
Most of the rocks on the ground along the highway are rounded cobbles, covered in a thick cortex of caliche. Shatter cones are extremely scarce, but present in eroded cobbles, or evident when some cobbles are broken. Cracking several caliche-covered cobbles with a rock hammer revealed that a surprising percentage of the material within the annular basin, even though it is only subtly expressed topographically, is actually impactite material from the crater rim or central peaks. Brecciated material and intensely fractured rock is abundant.
Most of the impactite along the roadway appears to be carbonate breccias, limestone or dolostone, with minor chert, and all of the shatter cones that we spotted appeared to be formed in the same sort of carbonate material.
At closest approach, the road rises on the flanks of the uplift itself. We noticed abundant iron oxide or iron sulfide nodules in this area, perhaps resulting from prolonged hydrothermal activity following the impact, or from some later regional mineralizing event borrowing the fractures that the impact had formed.
This is one of the largest impact craters in the United States, and even after having worked on 4 to 5 km craters for several years, I found it challenging to take in the scale of the structure. It defines the shape of the vast, open landscape in every direction.
Highway 385 exits the crater through a low point in the remnants of the south rim, shown above. Both boundaries are clearly marked, and both perspectives give an excellent sense of the scale of the structure. One should consider that the vast majority of both the rim and central peak have been removed by millions of years of weathering.
Sierra Madera crater may be the easiest-to-find crater in the US, next to Barringer, in Arizona. From Fort Stockton, which is located on Interstate 10, in west Texas, drive south on Hwy 385. The center of the crater is about 21 miles from Fort Stockton, and the crater perimeter is marked by signs. You can watch the central uplift rise in the distance all the way from Fort Stockton.
Closer in, the road takes you right through the crater in a way that could hardly have been planned to proved better viewing. The shoulders of the highway are very wide. Please be considerate by not trespassing on private roads or crossing fences.
Bibliography and References:
(If links to articles don't work, don't give up. Try pasting the link shown into a search engine or searching for the article authors, title, or other reference information. If your research leads you to additional scientific references related to this crater, please help improve this resource by sending a note with the new citation(s) to: email@example.com )
Adachi T., Kletetschka G. (2008) Impact-pressure controlled orientation of shatter cone magnetizations in Sierra Madera, Texas, USA. Studia Geophysica et Geodaetica Volume 52, No. 2, pp. 237-254.
Boon J. D., Albritton C. C. Jr. (1937) Meteorite Scars in Ancient Rocks. Field and Laboratory, volume 5, number 2, pp. 53-64.
Boon J. D., Albritton C. C. Jr. (1938) Established and supposed examples of meteoritic craters and structures. Field and Laboratory, volume 6, number 2, pp. 44-56.
Constant F. L. (1978) The Elsinore; Pikes Peak, East; GMW; and Sierra Madera Fields of Pecos County,Texas, in Gilbertson, R., ed., Energy Quest of the Southwest SWS AAPG Annual Meeting, 1978, West Texas GeologicalSociety, volume 78-69, p. 61-70.
Dennie D., Elmore R. D., Huson S. A., Madden M. E. (2007) Paleomagnetism of the Sierra Madera impact structure, Texas (abstract). Abstracts of the 2007 GSA Denver Annual Meeting, Geological Society of America Abstracts with Programs, Volume 39, No. 6, p. 372.
Dietz R. S. (1960) Meteorite impact suggested by shatter cones in rock. Science, Volume 131, No. 3416, pp. 1781-1784 doi: 10.1126/science.131.3416.1781
Donofrio, R. R. (1997) Survey of hydrocarbon-producing impact structures in North America: Exploration results to date and potential for discovery in Precambrian basement rock, in Ames Structure in Northwest Oklahoma and Similar Features: Origin and Petroleum Production (1995 Symposium), Johnson, K. S. and Campbell, J. A., eds. Oklahoma Geological Survey, Circular 100, pp. 17-29.
Donofrio R. R. (1998) North American impact structures hold giant field potential. Oil and Gas Journal, May 1998 issue, pp. 69-83.
Dulin S. A., Elmore R. D., Dennie D. P., Evans S. C., Mulvany P., (2011) Paleomagnetic Investigations of the Decaturville, MO, and Sierra Madera, TX, Impact Structures (abstract #1120), Abstracts of the 42nd Lunar and Planetary Science Conference
Eggleton R. E., Shoemaker E. M. (1961) Breccia at Sierra Madera, Texas. in Short Papers in the Geologic and Hydrologic Sciences, Articles 293-435, United States Geological Survey Professional Paper 424-D, pp. D151-D153.
French B. M. (1984) Impact event at the Cretaceous-Tertiary boundary: A possible site. Science, Volume 226, No. 4672, p. 353. doi: 10.1126/science.226.4672.353-a
Geyer R. A., Van Lopik J. R. (1963) Reconnaissance geophysical survey of the Sierra Madera, Texas 'Dome' and its lunar implications (abstract). Abstracts of the 44th Annual Meeting of the AGU, EOS Transactions of the American Geophysical Union, Volume 44, No. 1, p. 76, doi: 10.1029/TR044i001p00003
Goldin T. J., Wünnemann K., Melosh H. J., Collins G. S. (2005) Hydrocode modeling of the Sierra Madera impact structure (abstract). Abstracts of the 36th Lunar and Planetary Science Conference.
Goldin T. J., Wünnemann K., Melosh H. J., Collins G. S. (2006), Hydrocode modeling of the Sierra Madera impact structure. Meteoritics & Planetary Science, Volume 41, Issue 12, pp. 1947–1958. doi: 10.1111/j.1945-5100.2006.tb00462.x
Howard K. A., Offield T. W. (1968) Shatter cones at Sierra Madera, Texas. Science, Volume 162, No. 3850, pp. 261-265 doi: 10.1126/science.162.3850.261
Howard K. A., Offield T. W., Wilshire H. G. (1972) Structure of Sierra Madera, Texas, as a Guide to Central Peaks of Lunar Craters. Geological Society of America Bulletin, Volume 83, No. 9, pp. 2795-2808 doi: 10.1130/0016-7606(1972)83[2795:SOSMTA]2.0.CO;2
Huson S. A. (2006) Field Guide to the Sierra Madera Impact Structure, prepared for the Impact Field Studies Group field trip, in association with the 37th Lunar and Planetary Science Conference. In Huson S. A. (2009) Quantitative Analysis of the Deformational History and Timing of the Sierra Madera Impact Structure, West Texas, Doctoral Dissertation, Washington State University. Chapter 5, pp. 105-140.
Huson S. A. (2009) Quantitative Analysis of the Deformational History and Timing of the Sierra Madera Impact Structure, West Texas, Doctoral Dissertation, Washington State University.
Huson S., Foit F., and Pope M., (2006), Comparison of shock-deformed carbonate samples to unshocked carbonate samples using X-ray powder diffraction (abstract #MR51B-0966). Abstracts of the America Geophysical Union 2006 Fall Meeting, San Francisco, CA.
Huson S., Foit F. F., Pope M. C. (2006) X-ray diffraction study at Sierra Madera impact structure, West Texas (abstract). Abstracts of the Southeastern Section 55th Annual Meeting of the Geological Society of America, GSA Abstracts with Programs, Volume 38, No. 3, p. 81.
Huson S. A., Foit F. F. Jr., Watkinson A. J., Pope M. C. (2006) X-ray diffraction powder patterns and thin section observations from the Sierra Madera impact structure (abstract #2377). Abstracts of the 37th Lunar and Planetary Science Conference.
Huson, S. A., Foit, F. F., Watkinson, A. J. and Pope, M. C. (2009), Rietveld analysis of X-ray powder diffraction patterns as a potential tool for the identification of impact-deformed carbonate rocks. Meteoritics & Planetary Science, Volume 44, Issue 11, pages 1695–1706. doi: 10.1111/j.1945-5100.2009.tb01200.x
Huson S. A., Pope M. C. (2005) Current research at the Sierra Madera impact crater, West Texas (abstract). Abstracts of the Geological Society of America Rocky Mountain Section 57th Annual Meeting, GSA Abstracts with Programs, Volume 37, No. 6, p. 5.
Huson S. A., Pope M. C., Foit F. F. Jr., Watkinson A. J. (2007) Immiscibility Features Between Silica-rich and Carbonate-rich Material in Breccia from the Sierra Madera Impact Structure (abstract #1817). Abstracts of the 38th Lunar and Planetary Science Conference.
Huson S., Pope M., Foit F., Watkinson A. (2007) X-ray powder diffraction as a tool for the identification of impact deformed rocks (abstract #U23A-0862). Abtracts of the American Geophysical Union, Fall Meeting 2007.
Huson S. A., Pope M. C., Watkinson A. J., Foit F. F. Jr (2005) Possible planar elements in zircon as indicator of peak impact pressures from the Sierra Madera impact crater, West Texas (abstract #2048). Abstracts of the 36th Lunar and Planetary Science Conference.
Huson S., Pope M., Watkinson A. J., Foit F. (2011) Deformational features and impact-generated breccia from the Sierra Madera impact structure, west Texas. The Geological Society of America Bulletin, Volume 123, No. 1-2, p. 371-383. doi: 10.1130/B30183.1
Kelly A. O. (1966) A water-impact hypothesis for the Sierra Madera structure in Texas. Meteoritics, Volume 3, Issue 2, pp. 79–82. doi: 10.1111/j.1945-5100.1966.tb00358.x
King D. T. Jr., Petruny L. W. (2007) Impact structures and craters of the U.S. Gulf coastal states. Gulf Coast Association of Geological Societies Transactions, Volume 57, p. 409-425.
Lowman P. D. Jr. (1965) Magnetic reconnaissance of Sierra Madera, Texas, and nearby igneous intrusions. Annals of the New York Academy of Sciences, Volume 123, Geological Problems in Lunar Research, pages 1182–1197. doi: 10.1111/j.1749-6632.1965.tb20427.x
Schultz P. H. (1997) Assessing Impact Trajectory in the Geologic Record (abstract). Abstracts of the Conference on Large Meteorite Impacts and Planetary Evolution (Sudbury 1997).
Shoemaker E. M., Eggleton R. E. (1964) Re-examination of the stratigraphy and structure of Sierra Madera, Texas. in Astrogeologic Studies Annual Progress Report, August 25, 1962, to July 1, 1963. United States Geological Survey, Open File Report, part B, pp. 98-106.
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Van Lopik J. R., Geyer R. A. (1963) Gravity and magnetic anomalies of the Sierra Madera, Texas, "dome". Science, Volume 142, No. 3588, pp. 45-47. doi: 10.1126/science.142.3588.45.
Wilshire H. G., Howard K. A. (1968) Structural patterns in central uplifts of cryptoexplosion structures as typified by Sierra Madera. Science, Volume 162, No. 3850, pp. 258-261. doi: 10.1126/science.162.3850.258
Wilshire H. G., Howard K. A., Offield T. W. (1971) Impact breccias in carbonate rocks, Sierra Madera, Texas. Geological Society of America Bulletin, v. 82, No. 4. pp. 1009-1018. 1971. doi: 10.1130/0016-7606(1971)82[1009:IBICRS]2.0.CO;2
Wilshire H. G., Offield T. W., Howard K. A., Cummings D. (1972) Geology of the Sierra Madera cryptoexplosion structure, Pecos County, Texas. U.S. Geological Survey Professional Paper 599-H. 41 pages.