A 50,000 year insect record from Rancho La Brea, Southern California: Insights into past climate and fossil deposition

QUATERNARY SCIENCE REVIEWS

卷:168

Article

Holden, Anna R.^1,2,3  Southon, John R.⁴  Will, Kipling⁵  Kirby, Matthew E.⁶  Aalbu, Rolf L.⁷  Markey, Molly J.⁸ 

[1] Amer Museum Nat Hist, Richard Gilder Grad Sch, 79th Cent Pk West, New York, NY 10024 USA

[2] Nat Hist Museum Los Angeles Cty, Dept Entomol, 900 Exposit Blvd, Los Angeles, CA 90007 USA

[3] La Brea Tar Pits & Museum, 5801 Wilshire Blvd, Los Angeles, CA 90036 USA

[4] Univ Calif Irvine, Dept Earth Syst Sci, Irvine, CA 92697 USA

[5] Univ Calif Berkeley, Essig Museum Entomol, Berkeley, CA 94720 USA

[6] Calif State Univ Fullerton, Dept Geol Sci, Fullerton, CA 92834 USA

[7] Calif Acad Sci, 55 Mus Concourse Dr, San Francisco, CA 94118 USA

[8] AIR Worldwide, 131 Dartmouth St, Boston, MA 02116 USA

关键词: Quaternary;    Paleoclimatology;    North America;    Radiogenic isotopes;    Paleoentomology;    Rancho La Brea Tar Pits;    Biostratigraphy;    Paleoenvironment;    Last Glacial;   

DOI  :  10.1016/j.quascirev.2017.05.001

来源: Elsevier

【 摘 要 】

Rigorously studied and dated Late Quaternary paleoenvironmental reconstructions from Ranch La Brea (RLB) and the Los Angeles Basin are scarce. Here, we use data from AMS radiocarbon dated insect fragments to infer local climates over the past 50,000 years. Our results indicate: 1) Quaternary insect remains can be located with great accuracy in radiocarbon time, and 2) well-dated and documented climate indicator beetle species are sensitive proxies for environmental change in the Los Angeles Basin. A total of 182 extant RLB ground and darkling beetle species (Coleoptera: Carabidae, Tenebrionidae) were radiocarbon dated. The resulting radiocarbon dates form a semi-continuous range from similar to 50 to 28, 16-7.5, and 4 kcal yrs BP to the present. Associated insect climate ranges indicate past conditions consistent with, or very similar to, the current Los Angeles Basin Mediterranean climate. Importantly, these insect data suggest higher temperatures and aridity than inferred previously from other RLB proxies. Furthermore, wider-than-assumed dating spreads for some deposits emphasize the lack of biostratigraphy for RLB, and challenge inferences based on limited sets of radiocarbon dates and assumptions about stratigraphic integrity. Our results demonstrate the necessity to independently radiocarbon date each taxon. The insect paleoclimate interpretations were compared to regional pollen data, primarily from various southern Californian sites including Lake Elsinore and Santa Barbara Basin. These comparisons reveal an important difference in climate interpretations for the last Glacial: the RLB insect data suggest climate similar to the current one, while the regional pollen data have been interpreted as indicating a climate wetter than present. (C) 2017 Elsevier Ltd. All rights reserved.

【 授权许可】

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