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INTRODUCTION
Over the past decade,14C calibration curves have improved substantially. Current calibration curves such as IntCal13 (Reimer et al. 2013), developed from tree rings and other annualized archives from temperate latitudes of the Northern Hemisphere, have been applied worldwide, including South America. However, atmospheric14C concentrations vary in both time and space (Braziunas et al. 1995), including a marked difference between the Northern and Southern Hemispheres, due to less atmospheric14C in the Southern Hemisphere (Lerman et al. 1970). Efforts to quantify this variation (Vogel et al. 1993; Stuiver and Braziunas 1998; McCormac et al. 1998) led to the development of the Southern Hemisphere calibration curve (McCormac et al. 2002), most recently refined as SHCal13 (Hogg et al. 2013a). In South America, SHCal is currently used by many paleoenvironmental scientists (e.g. Gao et al. 2012; Engel et al. 2014; Martel-Cea et al. 2016; Nelson and Sachs 2016; Weide et al. 2017) and archaeologists (e.g. Capriles and Albarracín-Jordan 2013; Levine and Stanish 2013; Koons and Alex 2014; Barberena et al. 2016; Jones et al. 2017). However, some archaeologists have questioned its applicability in tropical South America because of potential mixtures of air from the Northern Hemisphere (Finucane et al. 2007; Rick et al. 2009; Ogburn 2012; Marsh 2012, 2015). This issue is particularly relevant for South America because this continent spans parts of both hemispheres and experiences atmospheric mixing near the equator. This paper addresses the issue of which curve is more appropriate in tropical South America based on global models of14C in the atmosphere and modern regional climate dynamics.
The question of which curve to use in tropical South America has not been discussed in detail, in part because the difference in calibrated ages derived from the two curves is less than a century. This difference is negligible for many paleoenvironmental processes operating over long temporal scales but can be significant for shorter time-scale dynamics, such as those relevant to past human activities. As long as a set of dates is calibrated with the same curve, the order and estimated time span of climatic or archaeological events will be consistent. Difficulties may emerge, however, when attempting to compare paleoenvironmental...