DOI: 10.25921/p06r-qz88
title: NOAA/WDS Paleoclimatology - US Pacific Coast Marine Terrace Quaternary Aminostratigraphy

description: Recent studies using the extent of racemization of amino acids to date fossil mollusc shells in the Arctic, the British Isles and on the Atlantic and Pacific coasts of North America have relied mainly on theoretical kinetic models of racemization. Ages generated in this fashion are highly model dependent and require estimates of integrated long-term diagenetic temperatures. We present here an alternative, empirical approach to aminostratigraphy in which we plot amino acid enantiomeric ratios versus latitude (for localities along the Pacific coast of the United States), and generate isochronal correlations by connecting data points of geographically proximal localities that have similar D:L ratios and zoogeographic aspect. Isochrons are calibrated at a few localities by independent radiometric dates. The diagenetic temperature effect on racemization is reflected in the slope of the isochrons, but the need to quantify temperature is eliminated.
description: Extent of Racemization (D/L) data for mollusks from Pleistocene 
marine terrace deposits along the US Pacific coast between 
Puget Sound, WA and San Diego, CA. 

Samples collected by numerous investigators, primarily K.R. Lajoie 
(US Geological Survey), G.L. Kennedy (USGS and Los Angeles County 
Museum of Natural History), J.F. Wehmiller, Univ. of Delaware. 
Some samples from existing USGS collections 
also included.  Samples collected and prepared between 1975 and 1981. 
Samples prepared and analyzed at the University of Delaware, Newark DE, 
Lab PI John F. Wehmiller.  Some samples analyzed by D. J. Blunt, USGS 
and at the University of Alberta. Analyses at UC San Diego are compiled 
here and included in Kern and Rockwell (1992). 
 
Locality number is from Kennedy et al. 1982 Figures 1 and 2 
Locality name is from Kennedy et al., 1982 Figure 1 

Locality designation lists field numbers or museum locality numbers: 
LACMIP = Los Angeles County Museum of Natural History 
HSU = Humboldt State University 
M = US Geological Survey 
CAS = California Academy of Science 
UCLA = Univ. California Los Angeles 
SDSU = San Diego State University 



Pretreatment: Fragments cut from shell valves; surface cleaning 
with dental tools; dilute HCl and distilled water wash; air dry 
AA fraction="amino fraction" 
THAA = total hydrolyzable amino acids;  
FAA = free amino acids (zero hydrolysis time) 
Hydrolysis procedure: 6N HCl 22 hours 105 deg C (for THAA only) 
Bleach: No 
Instrumental programming: GC temperature program; HPLC buffer gradient 
Blank corrections: no 
Response factors: no  
D/L values reported as peak height ratios 

Lab Code 
UDEL= University of Delaware; 
USGS = U. S. Geological Survey, Menlo Park, CA; 
UCSD = Univ. California San Diego

Sample ID = identity of specific shell analyzed 
Analytical method: GC = gas chromatography, used for multiple amino acids; 
HPLC used for determination of A/I values 
Subsample ID =  usually the same as sample ID; repeat fragments of same 
shell will have unique identification 
Ratio type = Peak Height ratios used for all results from GC; 
peak area ratios assumed for all results for HPLC 

D/L values are reported as the means of multiple chromatograms, 
usually at least 3. For GC results, in most cases sample derivatives 
were analyzed using more than one GC column. 

Samples selected for analysis were chosen because they appeared 
to be the most robust specimens among those available,  In most cases, 
samples were not whole valves.  Abraded, rounded, or chalky fragments 
were avoided where possible, and multiple shells from each collection 
were analyzed in almost all cases.  No data screening procedures 
have been applied.  No interlab sample comparisons were made 
during the period of these analyses.

Information on sample quality (fragment, whole shell, abraded, 
chalky, etc.) will be compiled for a future version of this datafile.

Abbreviations:

A/I     D-alloisoleucine/L-isoleucine
Ala     Alanine
Asx     Aspartic acid and asparagine
Glx     Glutamic acid and glutamine
Leu     Leucine
Phe     Phenylalanine
Pro     Proline
Val     Valine

P = Protothaca
S = Saxidomus
M = Macoma
C = Chione
T = Tivela

9999 = no data available for this amino acid in this sample