麻豆传媒

The Pennsylvanian Joggins Formation was deposited in the Cumberland Basin of Nova Scotia, a fault-bounded depocenter within the regional Maritimes Basin. Famous for its upright fossil lycopsid trees, the coastal exposure of this unit is widely regarded as the world=s best exposure of coal-bearing Carboniferous strata. The newly redefined Joggins Formation comprises a small part of the 4, 441-m-thick AJoggins section,@ which was measured by Sir William Logan during a 5 day period in June of 1842.

New seismic reflection data show that the Joggins Formation thickens towards the center of the Athol Syncline and thins on the flanks of the adjacent, salt-cored Anticlines. These observations indicate that much Early Pennsylvanian subsidence in the Athol Syncline resulted from syndepositional flow of the underlying Windsor Group salt into the adjacent salt-cored anticlines (diapirs). This motif of ongoing, relatively gradual subsidence provides a mechanism to explain the exceptionally rapid accumulation of the Joggins Formation, as well as the lack of erosional sequence boundaries, basinward facies shifts, and other characteristics common to alluvial strata deposited in coastal areas.

Rivers sourced in the Caledonia Highlands and the New Brunswick Platform supplied sediment to this part of the basin during the Pennsylvanian. These rivers ranged from broad, sheet-like channel bodies in the Lower Cove redbeds, to the fixed, meandering, and multistorey channel bodies of the coal-bearing Joggins Formation. Statistical analysis of the width (W) and thickness (T) of the Joggins channel bodies shows that they represent distinct, but non-exclusive, areas in W-T space. Several multistorey channel bodies are present in the section, but high subsidence and sedimentation rates prevented rivers from extensively reworking preexisting fluvial deposits - thus preserving a remarkable amount of information about the rivers that formed them.

The heterolithic floodplain strata that encase these channel bodies contain a suite of hydrodynamic and decay-related sedimentary structures that formed where standing plants interacted with the sediment-laden floodwaters that regularly inundated the floodplain. These vegetation-induced structures are also present in the Mississippian Horton Group of Nova Scotia and New Brunswick, indicating that the fossil record of plant-sediment interaction may be much richer than previously recognized.

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Pages: 516
Supervisor: Martin Gibling