. Bulletins of American paleontology. Baja California Stratigraphy: Carreno and Smith 75 1 112° 'W â² K-Ar locality A microfossils 0 5 1KM N / m A / 'C .^â¢^' / y yS° Bahia (^O' Vaporeta J ^y â ^ V. ST., /"W'i â \> \«ffl, Punta /^V>Vv \ K°^.. W 28° Ensenada Blanca ^/ ^ ^\'i' ' n^"^ ^â ^- 'N A ^^ ^"i \ S *^% /l^^ 3 -^ C> Vt ^. - ®^^ X 1 Cerro ^S \^- J ^l^Starship > \\\ -v PuntaC ;;^ %.. -- ^ % \^, Willard \^'â-^~^^ Isla Tiburon Text-figure 47.âSouthwestern Isla Tiburon. Sonora. locality map modified from Smith ( l^Qlc). Middle to Late Miocene
. Bulletins of American paleontology. Baja California Stratigraphy: Carreno and Smith 75 1 112° 'W â² K-Ar locality A microfossils 0 5 1KM N / m A / 'C .^â¢^' / y yS° Bahia (^O' Vaporeta J ^y â ^ V. ST., /"W'i â \> \«ffl, Punta /^V>Vv \ K°^.. W 28° Ensenada Blanca ^/ ^ ^\'i' ' n^"^ ^â ^- 'N A ^^ ^"i \ S *^% /l^^ 3 -^ C> Vt ^. - ®^^ X 1 Cerro ^S \^- J ^l^Starship > \\\ -v PuntaC ;;^ %.. -- ^ % \^, Willard \^'â-^~^^ Isla Tiburon Text-figure 47.âSouthwestern Isla Tiburon. Sonora. locality map modified from Smith ( l^Qlc). Middle to Late Miocene dacites. and rhyo- lites between 13 Ma and 9 Ma that ate inteibedded with Of unconttirmably ovetiie the tnarine conglom- eiate. All units bear infotmal lithostiatigtaphic desig- nations rather than formal formation names (Gastil et uL, 1999). UniuiiiiccI voUciiiic rocks. Units M1-M7 of Gastil et al. (1999). Early and Middle Miocene.âThe volcanic units, part of the magmatic arc that existed from 24 to 1 1 Ma in the area of the present Gulf of California, were studied by Neuhaus (1989a,b) and Neuhaus et al. (1988). They include andesitic flows and breccias of Ma. tuffs, flows, and breccias of Ma: they are designated Units M1-M7 as detailed by Gastil ci (//. (1999). who reported radiometric dates for 22 samples. These ages fall within the 24-1 1 Ma range published for volcanic rocks in the Sietra Santa Ursula east of Guaymas. Sonora (Mora-Alvarez and McDow- ell. 2000). Unnamed coni;loinerate and sandstone. Unit M8 of Gastil el al. (1999). Miocene to Early Pliocene.âThe primarily marine sandstt)ne and pebble to cobble and boulder conglomerate is a unitiue ()-m-thick unit. Text-Hgure 4S.âMiocene \olca]iic breccia, southwestern Isla Ti- buron. Ciastil (7 <(/. ( IW^I reported a K/Ar age of ± Ma lor a Mionomicl breccia interbeddcd with marine conglomerate in â Arroyo 3" (sample S3BSJ2(iO). Photo. J. G. Smith. I9S3;
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