Chemical+Limnology



THE PERCENTAGE OF ORGANIC MATTER IN THE SEQUENCE VARIES SUBSTANTIALLY. IN A VERY GENERAL WAY, HIGHER ORGANIC CONTENT CORRELATES WITH LOWER ELEMENTAL CONCENTRATIONS IN THE SEDIMENT. THIS RELATIONSHIP, AS WELL AS THE DIATOM ANALYSIS, SUGGESTS THAT AS THE INFLUX OF ALLOGENEIC SEDIMENT SLOWED, LAKE PRODUCTIVITY ROSE. THE CONCENTRATION OF CHARCOAL, HOWEVER, IS THOUGHT TO BE RELATED TO FIRE IN THE CATCHMENT, WHICH, IN TURN, MAY HAVE LED TO AT LEAST A BRIEFOF INSTABILITY AND INCREASED EROSION. THESE DISTURBANCE STAGES ALSO APPEAR TO CORRELATE WITH ‘DISTURBANCES’ IN THE POLLEN AND DIATOM RECORD. LAMINAE OF NEARLY PURE CLAY ARE SCATTERED THROUGHOUT THE CORE, BEING MOST COMMON IN THE INTERVAL BETWEEN 2.12 AND 4.47 M. THESE CLAY-RICH LAMINAE ARE ALL LESS THAN 4MM THICK AND MAINLY <2 MM THICK. X-RAY DIFFRACTION ANALYSES OF CORE VHB SHOWED THE PRESENCE OF A SIMILAR SUITE OF MINERAL THROUGHOUT THE SEQUENCE. NO ATTEMPT WAS MADE TO QUALIFY THE PERCENTAGES OF THESE MINERALS. IN ALL THIRTY-THREE SUB-SAMPLES THE MAJOR MINERALS IDENTIFIED WERE AUGITE, OLIVINE, HAEMATITE, PLAGIOCLASE AND MAGNETITE. LESSER PROPORTIONS OF QUARTZ, POTASSIUM FELDSPAR, AND CALCITE ARE PRESENT IN MOST SAMPLES. UNDER MICROSCOPE, IT APPEARS THAT HAEMATITE IS PRESENT AS A STAIN OR ALTERATION PRODUCT ON SOME GRAIN. ANALYSES OF MAJOR ELEMENT OXIDES, ORGANIC MATERIAL, AND CHARCOAL FROM THE VHA CORE ARE SHOWN IN PERCENTAGE FORM. THERE IS NOT A DISTINCT OVER TREND IN THE MAJOR OR TRACE ELEMENTS, ALTHOUGH THERE IS AN IN-PHASE RELATIONSHIP IN MANY LAMINAE. ANALYSIS FOR CU AND NI AT EIGHT INTERVALS SCATTERED THROUGHOUT CORE VHB SHOWED VALUES RANGING FROM 90 TO 129 PPM AND FROM 146 TO 246 PPM, RESPECTIVELY, WITH NO TREND CHLORIDE CONTENT IN THE SEDIMENT WAS UNPREDICTABLE.