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Alamo Breccia

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Series: Geological Society, London, Special Publications
Published: 01 January 2013
DOI: 10.1144/SP371.8
EISBN: 9781862396340
... Abstract The Devonian Alamo Breccia is a thick (<30–130 m) unit, interpreted as a bolide impact deposit, which is bracketed by marine carbonates. Samples were collected within the breccia and above/below the breccia for a contact test to determine if the breccia acted as a conduit for fluids...
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Published: 01 January 2002
DOI: 10.1130/0-8137-2356-6.489
Journal Article
Journal: Geology
Published: 01 November 1995
Geology (1995) 23 (11): 1003–1006.
...Hugues Leroux; John E. Warme; Jean-Claude Doukhan Abstract A transmission electron microscope (TEM) study of quartz grains strongly implies that the Alamo breccia of southern Nevada resulted indirectly from a Late Devonian hypervelocity impact event. The Alamo breccia is perhaps the most voluminous...
Published: 01 January 2007
DOI: 10.1130/2008.2437(07)
... Based on evaluation of past results and new research, we have partitioned the distribution of the Alamo Breccia in southeastern Nevada and western Utah into six genetic Realms that provide a working model for the marine Late Devonian Alamo Impact Event. Each Realm exhibits discrete impact...
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Publisher: Society for Sedimentary Geology
Published: 01 January 2017
DOI: 10.2110/sepmsp.107.11
EISBN: 9781565763456
... of sedimentation before, during, and after the Devonian (Frasnian) Alamo impact event (382 Ma), evidenced mainly by the regional Alamo Breccia Member of the Guilmette Formation. Two transects arranged from seven stratigraphic sections measured through the lower ~300 m of the Guilmette Formation record...
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Series: GSA Field Guide
Published: 01 January 2008
DOI: 10.1130/2008.fld011(10)
EISBN: 9780813756110
... of North America. In the middle- to outer-platform settings, Devonian strata reach a thickness of over 1800 m ( Fig. 3 ). Devonian Geologic Summary Figure 9. Alamo Breccia locality map showing genetic Breccia Realms, Nevada and western Utah. Lateral Breccia Zones 1, 2, and 3 of earlier...
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Journal Article
Journal: Geosphere
Published: 01 February 2015
Geosphere (2015) 11 (1): 123–143.
...Andrew J. Retzler; Leif Tapanila; Julia R. Steenberg; Carrie J. Johnson; Reed A. Myers Abstract Marine facies of carbonate and siliciclastic sediments deposited on top of the upper Devonian Alamo Breccia Member identify the shape and size of the Alamo impact crater in south-central Nevada (western...
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Series: GSA Special Papers
Published: 01 October 2015
DOI: 10.1130/2015.2517(02)
... of the eastward-traveled outer crater rim created by the ca. 382 Ma (early Late Devonian, middle Frasnian) Alamo impact. The Alamo impact was produced by a 5-km-diameter bolide, most likely a comet, which excavated a transient submarine crater 44–65 km in diameter. Comparison of thin (8–12 m) Alamo Breccia...
Published: 01 January 2005
DOI: 10.1130/0-8137-2384-1.259
... through multiple converging lines of geological and paleontological evidence. Previous and new evidence includes the catastrophically emplaced Alamo Breccia, tsunamites, shock-metamorphosed quartz grains, carbonate accretionary lapilli, an iridium anomaly, sub-Breccia clastic injection, deep-water Breccia...
Journal Article
Journal: PALAIOS
Published: 06 January 2020
PALAIOS (2020) 35 (1): 12–21.
...BENJAMIN E. RENDALL; LEIF TAPANILA ABSTRACT Conformable limestone deposits bracketing the Alamo breccia (Late Devonian, Nevada) provide a robust dataset for comparisons of depositional environments and marine communities before and after a significant meteor impact. Rank abundances of more than...
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Conceptual diagram showing a net gain or loss of thickness due to differential deposition of the Alamo Breccia Member. (A) Pre-impact deposition of the lower member of the Guilmette Formation. (B) Syn-impact detachment surface within the LFI (ledge-forming interval; lower member, Guilmette Formation) unit. (C) Differential deposition of impact breccia atop this detachment surface. AB—Alamo Breccia Member (Guilmette Formation); YSFI—yellow slope-forming interval (lower member, Guilmette Formation).
Published: 01 February 2015
Figure 3. Conceptual diagram showing a net gain or loss of thickness due to differential deposition of the Alamo Breccia Member. (A) Pre-impact deposition of the lower member of the Guilmette Formation. (B) Syn-impact detachment surface within the LFI (ledge-forming interval; lower member
Image
Transect BB' showing east-west stratigraphic relationships. Note thinning of Alamo Breccia to the east. Modified from Rendall and Tapanila (2016).
Published: 06 January 2020
Fig. 4.— Transect BB' showing east-west stratigraphic relationships. Note thinning of Alamo Breccia to the east. Modified from Rendall and Tapanila (2016) .
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Transect AA' showing northeast-southwest stratigraphic relationships. Note thinning and eventual pinchout of Alamo Breccia to the northeast. Modified from Rendall and Tapanila (2016).
Published: 06 January 2020
Fig. 3.— Transect AA' showing northeast-southwest stratigraphic relationships. Note thinning and eventual pinchout of Alamo Breccia to the northeast. Modified from Rendall and Tapanila (2016) .
Journal Article
Published: 01 July 2006
Journal of Paleontology (2006) 80 (4): 760–767.
... the Frasnian Guilmette Formation of Nevada, which includes breccias of the Alamo Bolide Impact. The borings occur in skeletal substrates both within and above the impact event breccias, demonstrating their existence prior to the impact and their survival of the catastrophic event. The Nevada discovery extends...
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Figure1—Entobia devonica n. comb. from the Late Devonian (Frasnian) Guilmette Formation, eastern Nevada. 1, Map of Nevada showing Mount Irish (MI) and Hancock Summit (HS) with a generalized stratigraphic column of the Guilmette Formation showing occurrences of E. devonica from stromatoporoids (*) and megalodont bivalves (§) at these two localities; 2, bedding-plane view of borings in recrystallized megalodont bivalves of the Upper Member, Hancock Summit; 3–7, borings in cobble-sized stromatoporoid clasts within the Alamo Breccia Member, Mount Irish, 3, branching canals with chamber preserved by dolomite fill in positive epirelief, 4, geopetal-filled chambers (up originally to the left), 5, acid-etched chamber and galleries filled with dolomite rhombs; note that fluting of dark stromatoporoid surface is an artifact of etching process, UUIC 04053.01, 6, spar-filled chambers, 7, vertical section through a high domal stromatoporoid showing boring chambers and canals; 8, top view of bored domal stromatoporoid in growth position surrounded by Amphipora thickets, above Alamo Breccia Member, Mount Irish; All scale bars = 1 cm
Published: 01 July 2006
stromatoporoids (*) and megalodont bivalves (§) at these two localities; 2, bedding-plane view of borings in recrystallized megalodont bivalves of the Upper Member, Hancock Summit; 3 – 7, borings in cobble-sized stromatoporoid clasts within the Alamo Breccia Member, Mount Irish, 3, branching canals
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Figure 3. Partly restored paleogeographic map, Nevada and western Utah, showing representative positions of the carbonate-shelf margin through the Devonian; see Figure 1 for conodont biochronology. Position of punctata Zone margin is prior to eastward shift (Fig. 6) produced by the Alamo Impact and formation of the Alamo Breccia, indicated in figure. Apparent juxtaposition of carbonate-shelf margin positions in northern Nevada is largely due to Antler orogenic compression and overthrusting. Approximate position of western (87Sr/86Sr) = 0.706. Tristate basin and Tooele arch edge of continental crust is indicated by Sri are broad, persistent Devonian structural features (Sandberg et al., 1989; Poole et al., 1992). Positions of other Devonian intrashelf basins, including depositional sites of Middle Devonian Woodpecker Limestone (Elrick, 1996) and Upper Devonian–Mississippian Pilot Shale (Sandberg et al., 1989, 2003), are omitted for simplicity. Abbreviations: RMTS—Roberts Mountains thrust system; STS—Sevier thrust system; WF—Wells fault. Major Cenozoic strike-slip faults and time-rock transect line (Fig. 4) are also shown. Data from Johnson et al. (1989) and Sandberg et al. (1989, 2002).
Published: 01 April 2008
Impact and formation of the Alamo Breccia, indicated in figure. Apparent juxtaposition of carbonate-shelf margin positions in northern Nevada is largely due to Antler orogenic compression and overthrusting. Approximate position of western ( 87 Sr/ 86 Sr) = 0.706. Tristate basin and Tooele arch edge
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Figure 6. Partly restored, early Late Devonian paleogeographic map and tectonic cross section, southeastern Nevada. (A) Map showing inferred position of punctata Zone shelf margin (dashed red line) prior to Alamo Impact Event and diagrammatic eastward shift in margin (arrows and breccia fill pattern) as a result of shattering and downslope and craterward transport of shelf-margin rocks following the event. Genetic Alamo Event realms (Warme and Pinto, 2006; Pinto and Warme, 2008) are indicated. Black concentric curved lines within Ring Realm depict inferred annular ring faults, which are related to the Alamo Event, discussed by Warme and Kuehner (1998) and Pinto and Warme (2008). Maximum possible post-impact eastward shift in shelf margin (green dotted line) corresponds to onshore limit of Ring Realm (or Alamo Breccia Zone 2 of Warme and Sandberg, 1995; Warme and Kuehner, 1998; Morrow et al., 2005). Also shown are positions of initial Pilot and Woodruff basins that formed adjacent to the proto-Antler forebulge (bold dashed black line) during the succeeding Early hassi Zone. Closed blue circles denote selected important localities used to constrain map. Purple line connecting White-rock Canyon and Black Shade Well localities marks cross section in Figure 6B. Fine dashed lines delineate Nevada county boundaries. Abbreviations: Cnyn.—Canyon; Mtn.—Mountain; N.—Northern. Modified from Sandberg et al. (2003) and Warme and Pinto (2006). (B) Schematic west to east tectonic cross section during Early hassi Zone, showing positions of Antler allochthon, foreland basin, eastward-migrating proto-Antler forebulge, initial backbulge (Pilot) basin, and carbonate shelf. Inferred flexural loading extensional faults west of the forebulge are after Silberling et al. (1997), who proposed such features for the Mississippian foreland system. A similar tectonic model was proposed for the Late Devonian and Mississippian by Poole (1974). By the Early rhenana Zone, Black Shade Well was within the expanding Pilot basin (Sandberg et al., 1989; Morrow and Sandberg, 2003). Not to scale; actual west to east distance from toe of allochthon to forebulge axis may have been as much as 200–250 km. Modified from Goebel (1991), Giles (1994), and Giles and Dickinson (1995).
Published: 01 April 2008
Figure 6. Partly restored, early Late Devonian paleogeographic map and tectonic cross section, southeastern Nevada. (A) Map showing inferred position of punctata Zone shelf margin (dashed red line) prior to Alamo Impact Event and diagrammatic eastward shift in margin (arrows and breccia fill
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Figure2—Type specimens of Entobia devonica n. comb. in stromatoporoids. 1–4, Syntypes from the Middle Devonian of Iowa, originally figured in Clarke, 1921, 1, 2, NYSM–6763, 1, multiple empty borings preserved on underside of stromatoporoid skeleton, arrow is detailed in 2; 3, 4, NYSM–6764, 3, sediment-filled boring network viewed by transmitted light through 1 mm thick slab, 4, tracing of boring in 3; 5, 6,Fenton and Fenton's (1932) previously unfigured plesiotype, UC–37038, from Middle Devonian Cedar Valley Group, Iowa, 5, multiple chambers with at least one conspicuous intercameral canal (arrow), 6, large chamber with radiating primary galleries (white arrow) and multiple pin-prick apophyses (black arrows); 7, new plesiotype, UUIC 04053.02, from Frasnian Alamo Breccia Member, Guilmette Formation, Nevada, black arrow indicates apertural canal extending from chamber to outer surface of stromatoporoid (white arrow). All scale bars = 1 cm
Published: 01 July 2006
conspicuous intercameral canal (arrow), 6, large chamber with radiating primary galleries (white arrow) and multiple pin-prick apophyses (black arrows); 7, new plesiotype, UUIC 04053.02, from Frasnian Alamo Breccia Member, Guilmette Formation, Nevada, black arrow indicates apertural canal extending from
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Cross section along the north-south (A-A′) transect showing post-impact sequences 3 and 4. Reconstructed locality positions. Thicknesses of Alamo Breccia Member (AB) and underlying units are from Sheffield (2011) and Rendall (2013). Cross section was drawn using the typical bottom-up thickness approach. Approximate water depth representing HST4 deposition at locality GGS3 was used to determine sea level across the entire transect: ∼15 m, shallow ramp environment between sea level and fair-weather wave base (Tucker and Wright, 1990). DDB—Hancock Summit down-dropped block; GGS—Golden Gate south; HE—Hancock east; HN—Hancock north; HST—highstand systems tract; LFI—ledge-forming interval (lower member, Guilmette Formation); LST—lowstand systems tract; MMN—Monte Mountain north; MMS—Monte Mountain south; O.R. fault—outer rim fault; PTN—Pahranagat north; SL—sea level; TST—transgressive systems tract; YSFI—yellow slope-forming interval (lower member, Guilmette Formation).
Published: 01 February 2015
Figure 13. Cross section along the north-south (A-A′) transect showing post-impact sequences 3 and 4. Reconstructed locality positions. Thicknesses of Alamo Breccia Member (AB) and underlying units are from Sheffield (2011) and Rendall (2013) . Cross section was drawn using the typical bottom
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Cross section along the west-east (B-B′) transect showing post-impact depositional sequences 3 and 4. Reconstructed locality positions. Thicknesses of AB (Alamo Breccia Member, Guilmette Formation) and underlying units are from Sheffield (2011) and Rendall (2013). Cross section was drawn using a top-down thickness approach based on the approximate water depth represented in HST4 deposition at each locality. Approximate water depths are as follows: SMFN2, HCE1, HHN1, DMP1, and MIN2 = ∼15 m, shallow ramp environment between sea level and fair-weather wave base (Tucker and Wright, 1990); MI1 = 0 m, exposure and karsted reef top representing sequence boundary–correlative conformity surface SB-CC-4; MMN4 = ∼50 m, deep ramp between fair-weather wave base and storm wave base (Tucker and Wright, 1990). DMP—Hiko Hills south dump; FM—Fox Mountain Formation; HCE—Hiko Hills east-central; HHN—Hiko Hills north; HST—highstand systems tract; LFI—ledge-forming interval (lower member, Guilmette Formation; LST—lowstand systems tract; MI—Mount Irish; MIN—Mount Irish north; MMN—Monte Mountain north; O.R. fault—outer rim fault; SL—sea level; SMFN—Six Mile Flat north; TST—transgressive systems tract; YSFI—yellow slope-forming interval (lower member, Guilmette Formation).
Published: 01 February 2015
Figure 12. Cross section along the west-east (B-B′) transect showing post-impact depositional sequences 3 and 4. Reconstructed locality positions. Thicknesses of AB (Alamo Breccia Member, Guilmette Formation) and underlying units are from Sheffield (2011) and Rendall (2013) . Cross section