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Title: Comparing MICADAS Gas Source, Direct Carbonate, and Standard Graphite 14C Determinations of Biogenic Carbonate
Abstract Northern Arizona University, Flagstaff, Arizona, USA, recently installed a MIni CArbon DAting System (MICADAS) with a gas interface system (GIS) for determining the14C content of CO2gas released by the acid dissolution of biogenic carbonates. We compare 48 paired graphite, GIS, and direct carbonate14C determinations of individual mollusk shells and echinoid tests. GIS sample sizes ranged between 0.5 and 1.5 mg and span 0.1 to 45.1 ka BP (n = 42). A reduced major axis regression shows a strong relationship between GIS and graphite percent Modern Carbon (pMC) values (m = 1.011; 95% CI [0.997–1.023], R2= 0.999) that is superior to the relationship between the direct carbonate and graphite values (m = 0.978; 95% CI [0.959-0.999], R2= 0.997). Sixty percent of GIS pMC values are within ±0.5 pMC of their graphite counterparts, compared to 26% of direct carbonate pMC values. The precision of GIS analyses is approximately ±7014C yrs to 6.5 ka BP and decreases to approximately ±13014C yrs at 12.5 ka BP. This precision is on par with direct carbonate and is approximately five times larger than for graphite. Six Plio-Pleistocene mollusk and echinoid samples yield finite ages when analyzed as direct carbonate but yield non-finite ages when analyzed as graphite or as GIS. Our results show that GIS14C dating of biogenic carbonates is preferable to direct carbonate14C dating and is an efficient alternative to standard graphite14C dating when the precision of graphite14C dating is not required.  more » « less
Award ID(s):
2041667 2127623 2127644
PAR ID:
10506563
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Publisher / Repository:
Cambridge University Press
Date Published:
Journal Name:
Radiocarbon
Volume:
66
Issue:
2
ISSN:
0033-8222
Page Range / eLocation ID:
295 to 305
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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