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Title: Nacre tablet thickness records formation temperature in modern and fossil shells

Nacre, the iridescent outer lining of pearls and inner lining of many mollusk shells, is made of periodic, parallel, organic sheets alternating with aragonite (CaCO 3) tablet layers. Nacre tablet thickness (TT) generates both nacre's iridescence and its remarkable resistance to fracture. Despite extensive studies on how nacre forms, the mechanisms controlling TT remain unknown, even though they determine the most conspicuous of nacre's characteristics, visible even to the naked eye.Thermodynamics predicts that temperature (T) will affect both physical and chemical components of biomineralized skeletons. The chemical composition of biominerals is well-established to record environmental parameters, and has therefore been extensively used in paleoclimate studies. The physical structure, however, has been hypothesized but never directly demonstrated to depend on the environment. Here we observe that the physical TT in nacre from modern and fossil shallow-water shells of the bivalves Pinna and Atrina correlates with T as measured by the carbonate clumped isotope thermometer. Based on the observed TT vs. T correlation, we anticipate that TT will be used as a paleothermometer, useful to estimate paleotemperature in shallow-water paleoenvironments. Here we successfully test the proposed new nacre TT thermometer on two Jurassic Pinna shells. The increase of TT with T ismore » consistent with greater aragonite growth rate at higher T, and with greater metabolic rate at higher T. Thus, it reveals a complex, T-dependent biophysical mechanism for nacre formation.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5] ;  [5] ; ORCiD logo [6] ;  [6] ;  [6] ;  [4] ;  [6] ;  [5] ;  [6] ;  [7] ;  [6]
  1. Univ. of Wisconsin, Madison, WI (United States); Harvard Univ., Cambridge, MA (United States)
  2. Harvard Univ., Cambridge, MA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  3. Harvard Univ., Cambridge, MA (United States); Univ. of New Mexico, Albuquerque, NM (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
  5. Univ. of Wisconsin, Madison, WI (United States)
  6. Harvard Univ., Cambridge, MA (United States)
  7. California Inst. of Technology (CalTech), Pasadena, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; FG02-07ER15899
Accepted Manuscript
Journal Name:
Earth and Planetary Science Letters
Additional Journal Information:
Journal Volume: 460; Journal Issue: C; Journal ID: ISSN 0012-821X
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1398582