Stratigraphy and paleomagnetism of the middle Eocene Friars Formation and Poway Group, southwestern San Diego County, California

Orbital pacing of Eocene climate during the Middle Eocene climate optimum and the chron C19r event - missing link found in the tropical western Atlantic

“…Our absolute ages for chron boundaries are slightly younger than in GPTS2012 Vandenberghe et al, 2012]. The ages in GPTS2004 [Ogg and Smith, 2004;Luterbacher et al, 2004] [Prothero and Emry, 1996;Walsh et al, 1996;Smith et al, 2010]. Our absolute ages are 400 kyr (C20n) and 200 kyr (C19n) younger than in CK95 [Cande and Kent, 1995].…”

New carnivoraforms (Mammalia) from the middle Eocene of California, USA, and comments on the taxonomic status of Miacis gracilis

“…42.5-42.0 Ma ago) following a revised age (based heavily on occurrences of rodents) for the Duchesnean Simi Valley Landfill local fauna. Importantly, while the absolute ages of the local faunas proposed by Lander (2011) and Kelly et al (2012) differ by approximately 1.5 to 2 million years, both of their proposals imply temporal proximity (greater than expected from Prothero et al's (1996) hypothesis in conjunction with the stratigraphic framework of Walsh et al, 1996) of the lower portion of middle member of the Sespe Formation, the lower portion of member C of the Santiago Formation, and the Mission Valley Formation, as was suspected by Walsh (1996). This point of agreement is further supported here by the stratigraphic distributions of Procynodictis progressus and 'Miacis' hookwayi (Figure 1.2).…”

“…Apataelurus" of Walsh, 1996, Although the biostratigraphic utility of mammalian carnivores is limited by their general rarity in the fossil record, the updated record of carnivoraforms presented here is valuable for evaluating the recent re-interpretations of the ages of various middle-Eocene local faunas in southern California (Lander, 2011;Kelly et al, 2012). Of particular interest are: 1) the Tapo Canyon and Brea Canyon local faunas, which belong to the lower portion of middle member of the Sespe Formation in Ventura County; 2) vertebrate assemblages from the Mission Valley Formation of San Diego County (an 40 Ar/ 39 Ar age of 42.83 ± 0.24 Ma ago from possibly the upper portion of this formation was reported by Walsh et al, 1996, and was recalculated as 43.45 Ma ago by Lander, 2011); and 3) the Jeff's Discovery local fauna, which belongs to the lower portion of member C of the Santiago Formation in San Diego County. Based on extensive magnetostratigraphic work in the Simi Valley area and the Uinta Basin, Prothero et al (1996) assigned the Tapo Canyon and Brea Canyon local faunas to Chron C18r (41.3-40.1 Ma ago; see Kelly et al, 2012), making them perhaps 1.3 to 3.1 million years younger than the above-mentioned assemblages from San Diego County.…”

“…See legend for color coding of various geologic formations. Temporal correlation of fossil assemblages, lithologic units, and magnetochrons follows Walsh (1996), Walsh et al (1996), Mihlbachler and Deméré (2009), and Kelly et al (2012), and generally should not be regarded as precise above one million-year resolution (cf. Walsh, 1996).…”

“…California, and Laredo Formation, Texas, USA, corresponding to the biochrons Ui2 and Ui3 of Uintan NALMA (cf. Dawson, 1980;Westgate, 1990;Walsh et al, 1996;Prothero, 2001;Robinson et al, 2004;Gunnell et al, 2009;Kelly et al, 2012), and possibly portions of the Friars Formation, California, corresponding to the biochron Ui1b (cf. Walsh et al, 1996;Robinson et al, 2004;Gunnell et al, 2009).…”