[The Journal of Geology, 2006, volume 114, p. 267–285]  2006 by The University of Chicago. All rights reserved. 0022-1376/2006/11403-0001$15.00 267 ARTICLES Reliability of Multitaxon, Multiproxy Reconstructions of Environmental Conditions from Accretionary Biogenic Skeletons Bernd R. Scho ¨ ne, 1 David L. Rodland, Jens Fiebig, Wolfgang Oschmann, David Goodwin, 2 Karl W. Flessa, 3 and David Dettman 3 Institute for Geology and Paleontology, INCREMENTS Research Group, Goethe University, Senckenberganlage 32-34, 60325 Frankfurt am Main, Germany (e-mail: b.r.schoene@em.uni-frankfurt.de) ABSTRACT Evaluation and quantification of climate change require data on subseasonal to daily environmental extremes from those periods before instrumental records were available. This study employs a high-resolution, multitaxon, multi- proxy approach and analyzes how faithfully accretionary biogenic skeletons record environmental extremes. Six specimens of two bivalve mollusks (Chione fluctifraga, Mytella guyanensi) and one barnacle species (Chthamalus fissus) from a single habitat (northern Gulf of California, Mexico) were collected. Contemporaneous shell portions from these specimens were analyzed for shell growth rates (sclerochronology) and stable isotopes (d 18 O, d 13 C) and were compared to instrumental records. The results of these analyses included some significant observations. First, shell d 18 O values overestimate winter temperatures and underestimate summer temperatures. Second, the actual diurnal temperature range is not recorded in the biogenic skeletons. Third, skeletal growth is biased toward a species-specific optimum growth temperature (24°–30.9°C). Therefore, higher sampling resolution will not necessarily capture actual environmental extremes. Despite measured temperature extremes of 37.8° and 4.5°C, none of the studied species recorded temperatures above 30.9° or below 12.2°C. Duration and timing of the annual growing period is species specific as well. Faster shell growth occurred at higher temperatures. Up to 58% (C. fissus) of the variability in shell growth can be explained by water temperature during growth. Contemporaneous trends in shell d 13 C show a weak correlation with pigment concentration ( ). Higher levels of chlorophyll appear to increase shell production 2 R p 0.17 rates. Our study highlights the difficulties inherent in using biogenic skeletons for the reconstruction of paleoenvi- ronmental extremes and demonstrates the power and utility of multiproxy and multitaxon approaches. Introduction Subseasonal and daily environmental extremes have recently become a focal point of studies on climate change (Kiktev et al. 2003; Klein Tank et al. 2005). During the past 3 decades, the number of global daily warm temperature extremes has in- creased more than twice as fast as the correspond- ing decrease in cold temperature extremes. This Manuscript received July 5, 2005; accepted December 12, 2005. 1 Author for correspondence. 2 Department of Geosciences, Denison University, 100 Sun- set Hill Drive, Granville, Ohio 43023, U.S.A. 3 Department of Geosciences, University of Arizona, Tucson, Arizona 85721, U.S.A. resulted in a significant rise in the seasonal tem- perature spread (Klein Tank and Ko ¨ nnen 2003). Evaluation and quantification of the anthropogenic impact on climate extremes and seasonality require data from preindustrial times. However, instru- mental records of environmental parameters cover only the past 150 yr or so (Jones et al. 2001). Con- sequently, high-resolution proxy archives of envi- ronmental variables would be of great benefit. Such records have been available since the early 1960s. However, in spite of recent theoretical studies (Goodwin et al. 2003; Ivany et al. 2003), it is still barely understood how reliable such proxy records really are.