PALEORIENT vol.6 1980 MICROMORPHOLOGY IN ARCHAEOLOGY AND PREHISTORY GOLDBERG

Introduction

Archaeologists with this term include prehisto- rians have long recognized the value of sedimentology and stratigraphy They realise that their ancient remains are encased within some kinds of materials that they intuitively feel should reflect upon the local environ ment before during or after occupation of the site In order to fulfil this intuition and reconstruct past environments geologists usually resort to their cache of tried and true techniques Those most familiar to ar chaeologists and sedimentologists alike are granulome- try heavy mineral analysis of the sand fraction and clay mineralogy of the fines and variety of chemical tests such as pH calcimetry organic matter content analysis of major elements etc Commonly however conditions arise that render such analyses of limited use For example what is the real meaning of total granulometrie analysis of sediment consisting of sand-sized aggregates of silt clay bone and coprolite fragments as documented at Hayo nim Cave)(l or of sample rich woody fragments intimately mixed with the mineral components Simi larly how can calcimetric determination distinguish between limestone grains deposited with the sediment from carbonate secondarily precipitated In other words given sediment as excavated may and more probably does represent the effects of more than one depositional or post-depositional event be it bio- anthro- or geogenie powerful technique that can get around these sorts of problems is that of micromorphology the study of sediments and soils in thin section and it is the aim of this note to make known to archaeologists and geolo gists alike the value of this technique in archaeological geology

Technical aspects

thin section is essentially 30 micron slice of rock soil or pottery mounted on glass slide For well indurated materials e.g. massive limestone or sands tone preparation is relatively simple the sample is cut with rock saw polished on one slide mounted on the glass slide and finally ground to the proper thickness For poorly consolidated materials like soils it is first necessary to harden the sample by impregnating it un der vacuum with liquid plastic such as epoxy or polyes ter resins The finished section is then ready for observa tion under the polarizing microscope The polarizing microscope permits wide range of observations of which will mention few of the more important ones Most apparent is the mineralogical and textural composition of the sediment the propor tions of sand silt and clay heavy mineral types bone rock fragments woody materials etc also clearly shown is the shape and degree of angularity of these components On higher level of organization it is possible to see the geometric interrelationships of these components such as illuviated clay filling voids graded bedding degree of aggregation of the matrix and types and distribution of pores It is intuitively obvious that many of these pheno mena should have interpretive value in discerning the origin of the sediment its mode of deposition and its 159