ORGANIC PETROGRAPHY OF CARBONACEOUS SHALES FROM THE LOWER DEVONIAN CAMPBELLTON AND VAL D’AMOUR FORMATIONS, NEW BRUNSWICK, CANADA

Eight samples of organic-rich shale from the Lower Devonian Campbellton and Val d’Amour Formations were collected from locations in New Brunswick, Canada, and examined by reflected light petrography. Samples from the Campbellton Formation are middle Emsian in age; those from the Val d’Amour Formation are Pragian to early Emsian in age. Proximate analyses indicate all of the samples to be high in ash (avg. 67.8 %), and low in sulfur (avg. 0.5 %). Petrographically, six of the samples had vitrinite reflectance values that ranged from 0.48 % to 1.0 % Ro maximum (high volatile bituminous C – A coal rank). Two samples, which had been subject to intense thermal alteration, had reflectance values of 4.48 and 5.22 % (anthracite to meta-anthracite).

All of the samples, except for the two thermally-altered samples, were high in vitrinite content (average 80.7 %, mineral matter free basis). Telovitrinite was the dominant vitrinite maceral subgroup, relative to detrovitrinite and gelovitrinite, in all of the samples (average TV/DV + GV ratio, 16.7:1), suggesting that either, 1) conditions within the paleomire were conducive to the overall preservation of organic matter (i.e., anoxic and acidic), resulting in high percentages of telovitrinite; or 2) the telovitrinite represents certain plant tissues that were highly resistant to decay. Liptinite macerals were moderate in abundance (average 18.7 % mineral matter free basis), and occurred primarily as sporinite. In two samples, cutinite was especially abundant. In these samples the cuticles, which were quite thick (commonly 20 to 30 microns), were separated by bands of telovitrinite that were arranged repetitively. In addition, the cuticles typically occurred as couplets, or were double-walled. Inertinite macerals were exceptionally rare (average 0.6 %, mineral matter free basis), which indicates either a paucity of wildfire during peat accumulation, or is a further reflection of acidic, anoxic conditions within the paleomire that not only promoted the formation of vitrinite, but also inhibited the formation of inertinite through degradational pathways.