47_ 



mineralogical composition. For this study, the term microfossil includes only foraminifera 

 and thecamoebians, some of which may have been living meiofauna at the time of 

 collection. Most microfossils are likely the shells of previously living organisms that have 

 been preserved with the accumulation of sediment since the last dredging operation in the 

 1960's. 



During the examination of the sediment samples for microfossils, observations of 

 minerals and other constituents were also recorded to assist in fumre dredged material 

 differentiation. Therefore, the term mineralogy also includes description of other 

 microorganisms such as diatoms and ostracods for this project. The abundances of all 

 parameters were noted and quantified, for statistical analysis of the mineralogy data, using 

 the following scheme: absent =0, rare=l, common =2, and abundant = 3. 



The fine fraction material was randomly sub-sampled with a metal spamla and 

 spread in a micropaleontology picking tray. Microfossils were picked until 100 specimens 

 of foraminifera were collected, or ten full trays of material had been analyzed. 

 Foraminiferal and thecamoebian tests, as well as diatoms and ostracods, were mounted in 

 cardboard slides with aluminum holders and glass cover slides and recorded. The grab and 

 core samples collected at the PDS contained a higher abundance of foraminifera relative to 

 the Royal River core samples. Therefore, microfossils were picked until 100 specimens 

 were collected or five micropaleontology picking trays were examined for each sample. 

 Following counting and identification of the microfossils, Scaiming Electron Microscopic 

 (SEM) photographs were taken of representative specimens (Figure 2-7). 



For displaying and interpreting data, the microfossils were grouped into five 

 categories based on a combination of factors: the identified informal group (foraminifera 

 or thecamoebian), the ecological zonation (freshwater, mudflat, marsh, or continental 

 shelf), and shell composition (agglutinated [silica] or calcareous) for foraminifera only. To 

 determine the relative abundance of freshwater thecamoebians, marsh foraminifera, 

 mudflat foraminifera, shelf agglutinated foraminifera, and shelf calcareous foraminifera, 

 the number of individuals per category were divided by the total number of individuals for 

 each sample. Relative abundance allows for comparison of samples despite differences in 

 density or volume of material examined and picked. To determine the density of 

 foraminifera and thecamoebians, the number of individuals were divided by the weight 

 (grams) of material picked. Microfossil densities may be correlated with environmental 

 conditions; for example, organic-rich silty clays may support larger populations than 

 coarse sand areas with a limited food supply. Both relative abundance and density data 

 were graphed, showing the position of the samples relative to the core. 



3.10 Multivariate Statistical Analyses of Fine Fraction Results 



The goal of the Royal River project was to define a tracer, or tracers, that would 



The Portland Disposal Site Capping Demonstration Project, 1995-1997 



