Post-Depositional Alteration of Calcium Carbonate Phases in Archaeological Ceramics: Depletion and Redistribution Effects

Abstract

The final stage in the life history of prehistoric pottery prior to archaeological recovery is usually the longest, and frequently the most dynamic. The remains of archaeological ceramics spend hundreds to thousands of years deposited within the upper layers of the earth’s crust where they encounter the same diagenetic environmental processes as the surrounding natural materials. Harsh conditions of subterranean environments induce physical stresses and chemical reactions, causing alterations of ceramic structure and composition. This is especially true of carbonate-rich ceramics, as carbonate phases are soluble when deposited within acidic environments. This paper examines common carbonate depletion and accretion effects of post-depositional environments on ancient ceramics from two rather different geological and archaeological contexts: Mesoamerica and the Mediterranean. Potters in both regions produce vessels with carbonate-rich materials—clays, calcite, limestone—that alter due to long exposure to low-pH sediments and continual water table fluctuations. Ceramic petrography is employed to identify traces of carbonate alterations within ceramic microstructure and to characterize fabrics. Elemental compositions of the same sherds are characterized through either scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS), inductively coupled plasma mass spectrometry and optical emission spectrometry (ICP-MS/OES) or neutron activation analysis (NAA). This method enabled comparison of the differing effects of post-depositional alteration of carbonate phases on bulk composition signatures commonly used to determine provenance.

Characterization of Ceramic Membrane based on Calcium Carbonate from Onyx Stone and Its Application for Coconut Sap Treatment

“…As a whole, the analysis of the SEM images indicates that the addition of onyx stone with content larger than 20% results in homogeneous interconnected and organized pores with a highly porous structure. The pores are produced due to the es capement of the gases [13] and ceramic expansion by the formation of crystalline anorthite and gehlenitesintering [23]. From this SEM observation, it can be said that the samples with an onyx stone content of 10 wt.% (CM1) and 20 wt.% (CM2) shows isolated pores and poor porosity if compared with other samples.…”

“…CaCO3 decomposes into calcium oxide (CaO) and carbon dioxide (CO2) at a temperature of above 650°C. The empty spaces formed by the release of CO2 gas bubbles during the sintering impart a porous texture to the membrane [13]. Because the commercially available CaCO3 is expensive, it is replaced by CaCO3 from onyx stone.…”

Chemical Analysis of prehistoric pottery complex of Valcorrente - Sicily (Italy)

“…The chemical compositions of all the 33 samples have been studied with PCA in order to look for possible similarities and differences among the various observed ceramic typologies using all the elements and excluding only the Calcium because it is susceptible to be attacked by groundwater circulation and it can be interested in the formation of secondary products [7][8]. The scatter plot of the data set in the plane of the two principal components PC1 and PC2, accounting for 18.9 % and 15.9 % respectively, is presented in Figure 2.…”

Crack Repair Model of Ancient Ceramics Based on Digital Image

“…For example, no scholar has applied the digital image to this field till now, so the research here is still a blank, which has great theoretical research and practical application value for crack repair. In addition, almost all crack repair models of ancient ceramics are shallow structure framework without deep feature extraction [28][29][30].…”