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Micropalaeontology and Palynology
Micropalaeontology is the study of microfossils which are not identifiable with the naked eye (Figure 1 ). Both the petrographic microscope and scanning electron microscope are essential tools for these studies. Palynology is a specialized area of micropalaeontology that deals with acid-insoluble organic plant fossils. Included in this classification are plant spores and pollen, which are associated with terrestrial environments. These data, when observed in core samples and related to sedimentary structures, texture and lithologic characteristics, help in the classification of environments of deposition. Figure 1 presents some examples of terrestrial and marine microfossils. Jones (2014) provides a state-of-the-art overview of all aspects of applied foraminifera studies and their applications in palaeoecology, biostratigraphy and sequence stratigraphy.
Trace Element Identification
Trace elements (an element in a sample that has an average concentration of less than 100 parts per million measured in atomic count, or less than 100 micrograms per gram) present in shales have been used successfully as a guide to major variations in the water salinity, and hence serve to differentiate between fresh water and marine sediments. The presence of trace elements is related to the cation exchange capacity of clay minerals located within the shales. Clays have very large surface areas and are often electrically imbalanced. Trace elements are adsorbed on clay surfaces, and many trace metals survive at these adsorptions points. Boron, chromium, copper, nickel, vanadium, rubidium and lithium are generally found in higher percentages in marine clay sediments deposited in salty water. Some studies have indicated lead associated with fresh water sediments.
Insoluble Residues
Tests for insoluble residues are conducted to determine the materials remaining after rock samples have been dissolved in hydrochloric, formic or acetic acid. Quartz, chert, pyrite and clay are common residues. The reporting of data may simply identify residues or may document their weight percentages as well. The techniques for such studies was discussed by Swanson (1981). Residue identification helps to specify the rock’s depositional environment. Pwa et al. (1999) discuss geochemical exploration using acid insoluble residues.
