Palynostratigraphic investigation of the Albert formation (Lower Carboniferous) of New Brunswick, Canada

Abstract

The Albert Formation, in the southeastern part of New Brunswick, contains oil shales from which oil and gas are produced (Stoney Creek field). The fauna and palynoflora of the formation suggest a terrestrial environment of deposition; there is no evidence of marine influence. The strata indicate a relatively shallow lacustrine environment with an associated fluvial deltaic sequence.

The preservation of palynomorphs in subsurface core samples from the lower member and middle oil shale member of the formation (Dawson Settlement and Frederick Brook Members, respectively) varies from very poor to very good, whereas preservation of palynomorphs in outcrop samples from the upper member (Hiram Brook Member) is very good. The poor preservation is probably the result of deposition under anoxic conditions, with the subsequent growth of pyrite on the exines; corrosion by microorganisms such as anaerobic bacteria or fungi may also have occurred.

No significant qualitative taxonomic variations were discernible in the palynoflora vertically throughout the formation. Quantitatively, most samples are dominated by Punctatisporites irrasus Hacquebard and P. planus Hacquebard; Spelaeotriletes pretiosus (Playford) Neves & Belt is common to abundant in two of the Hiram Brook samples. Dominance of a few species may indicate an arid climate consistent not only with Atlantic Canada's position of low latitude in the various paleocontinental reconstructions for the Early Carboniferous, but also with the local presence of evaporites in upper beds of the Albert Formation.

Comparison with assemblages from the Horton Group of Nova Scotia favors a correlation with the Horton Bluff Formation. The Albert Formation assemblages may be correlated with the Spelaeotriletes pretiosus‐Raistrickia clavata (PC) Spore Zone of Tournaisian, late Tn2 to early Tn3, age of western Europe.

The organic matter consists of significant amounts of algae (Botryococcus sp.) along with exinous, woody, and coaly fragments. The spores are yellow‐orange to orange‐brown, indicating a Thermal Alteration Index (on a five point scale) of 2‐ to 2+. This low level of maturation and the type of organic matter suggest some potential for the generation of liquid hydrocarbons.

Notes

Geological Survey of Canada Contribution No. 39286