Depositional and Environmental Interpretation of the Meander River Carbonate Sheet, Avondale, Hants County, Nova Scotia.

Abstract

Detailed investigation of the Lower Carboniferous Meander River carbonate sheet (Limestone 2, Subzone D of the Windsor Group) exposed at Avondale, Hants County, Nova Scotia, reveals a pair of incomplete, asymmetrical, transgressive and regressive cycles.

Lithologies present are: (1) ostracodal biosparite; (2) oosparite; (3) biosparite-calcisiltite; (4) flat-lying laminated pelsparite; (5) algal laminated pelsparite; (6) undulating laminated pelsparite; (7) pelsparite breccia and pseudobreccia; (8) sparitic mudstone and grainstone; (9) interbedded red and brown mudstones, siltstones, sandstones and conglomerates; and (10) laminated algal sparite.

Nine major zones were identified and they are (in ascending order): (1) marginal marine marsh; (2) oolitic shoals; (3) shoal lime sands; (4) subtidal to intertidal lagoon; (5) supratidal lagoonal fringe; (6) lagoonal intertidal flats; (7) calcrete soil; (8) alluvial fan mudflows and fluvial deposits and (9) a playa lake. The entire carbonate sequence is bounded above and below by massive red and green fluvial siltstones.

The initial transgression of the carbonate complex is represented by lithozones 1-3. A very rapid regression prevented the deposition of an inversion of lithozones 1-3 over the initial transgressive units, and resulted in the seaward progradation of the nearshore lagoonal facies 4. This is transitional to lithozone 5 which is slightly eroded and overlain by pelsparites of lithozone 6, representing a second, subdued transgressive pulse. Lithozone 6 probably continues on as a shallowing upwards sequence, but is obscured due to the later formation of a calcrete soil (lithozone 7) on the subaerially exposed sediments of lithozone 6. This soil is preserved by the rapid deposition of fanglomerate sediments of lithozone 8. Lithozone 9 is located within the sediments of lithozone 8.

The probable mechanism which controlled the rise and/or fall of the ancient sea level was basinal faulting and warping. Only very slight changes in bottom slope and/or elevation were required since water depths probably only ranged from 0-4 metres in this area.

Keywords: Pages: 164 Supervisor: Paul Schenk