Braided Stream Deposits of the Battery Point Formation, Gaspé, Québec

Abstract

<p>The Battery Point Formation (Devonian) Gaspé, Québec is interpreted as in part a braided stream deposit. Seven highly variable, dominantly fining upward sequences have been defined from the braided section. These differ from the sequences of meandering stream deposits in that overbank deposits comprise less than 10 percent of the braided sequences.</p> <p>A generalized sequence has been built consisting of an erosional intraclast-strewn surface, on which is deposited a unit of pebbly sandstone composed of large, (up to 10 ft wide) poorly defined trough crossbeds. Above this is a unit of medium sandstone composed of smaller, better defined trough crossbeds. Within each of these two units are intercalated large (1 to 10 ft) sets of planar tabular crossbeds. These deposits make up about 90 percent of the generalized sequence. Above this, small planar tabular corssbed sets and large scour fillings occur, but these comprise only about 5 percent of the sequence. Capping the sequence is interbedded rippled sandstone and mudstone, followed by a small unit of fine sandstone in low angle to flat strata which show parting lineations.</p> <p>The sequence is interpreted as resulting from the filling of a large channel within the braided system. The trough crossbedded sandstones are the deposits of migrating dunes. The large planar tabular crossbeds results from the building forward of linguoid bars. These dunes and bars are active channel deposits. The small planar tabular sets result from the migration of small delta-like bars and the scour fillings are caused by low stage fillings of high stage scours. The interbedded rippled sandstone and mudstone is a vertical accretion, floodplain-like deposit. The low angle strata above result from very high, swift floods sweeping over the emerged parts of the braided system.</p> <p>The sequence actually seen are highly variable, but all bear some resemblance to the generalized sequence.</p>