A comparative study of the change in diatom inferred ph of a staircase of lakes in the Algoma District, Northern Ontario /

Four staircase lakes occupying a single watershed located in the Algoma District, north of Lake Superior were chosen for this study. I examined the subfossil diatom assemblage in the top twenty centimeters of the surface sediments in each of these four lakes in an attempt to reconstruct their respective past pH history. From these analyses it was possible to test the hypothesis that the rate of change of diatom inferred pH was not significantly different in lakes located one below the other in a single "staircase" within a single watershed system. My results indicated that the four Z lakes had been acid for at least the last century. The water color of the three upper Z lakes (Z1, Z2 and Z3) was brown (>30 Pt Co units). The bottom lake (Z4) was the only clear water lake in the system «5 Pt Co units). This bottom staircase lake had no muskeg development around its shoreline. The alkaliphilous diatoms in the Z watershed system were important in determining the diatom inferred pH of the four Z lakes. The centric diatoms were extremely rare in the clearwater bottom lake (Z4). The ecology of the Eupodiscales is perhaps important in the interpretation of sediment in the more acid environment. Lake Z4 was the only one that had a progressive as well as a significant decrease in its downcore diatom inferred pH since the early 1960's. This lead me to speculate that the humic substances present in the upper three brown water lakes (Z1, Z2 and Z3) were perhaps Important in buffering them against a further decrease in water pH even though they were located within an area which was sensitive to acid precipitation.

Middle Ordovician (Whiterockian-Chazyan) trilobites from the Sunblood Formation, District of Mackenzie

The Middle Ordovician Sunblood Formation in the South Nahanni River area, District of Mackenzie, comprises mainly limestones and dolostones of intertidal and shallow subtidal origin as indicated by the presence of desiccation polygons, fenestral fabric, and oncolites. The study of well preserved, silicified trilobites from low diversity, Bathyurus-dominated, Nearshore Biofacies faunas of Whiterockian and Chazyan age collected in six stratigraphic sections through the Sunblood Formation permits the recognition of three new Whiterockian zones, and two previously established Chazyan zones. The Bathyurus mackenziensis, Bathyurus sunbloodensis, and Bathyurus margareti zones (Whiterockian), together with the Bathyurus nevadensis and Bathyurus granu/osus zones (Chazyan) represent the Nearshore Biofacies components of a dual biostratigraphic scheme that considers both temporal and spatial distribution patterns, and are compositionally distinct from faunas in correlative strata around North America that represent other biofacies. Twenty-six species belonging to eighteen genera are described and illustrated. Ludvigsenella ellipsepyga is established as a new bathyurine genus, in addition to four new species of Bathyurus : Bathyurus mackenziensis, Bathyurus sunbloodensis, Bathyurus margareti and Bathyurus acanthopyga. Other genera present are: Basilicus, Isote/us, ///aenus, Bumastoides, Fail/eana, Phorocepha/a,Ceraurinella, Acanthoparypha, Xystocrania, Cydonocephalus, Ectenonotus, Pseudomera, Encrinuroides, Calyptaulax, Amphilichas and Hemiarges.