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    Mulberry Run: Passive margin carbonate sedimentation during the Cambrian and Ordovician Periods

      Beekmantown Formati...


      The orientation of the continents at the time these limestones were being deposited. Virginia was located well south of the paleoequator at temperate to sub-tropical latitudes.

      In the diagram above, there is a lot going on. First, note that all sedimentary layers are deposited oldest to youngest and in an originally flat/horizontal orientation. In from oldest to youngest with the oldest on the bottom, here is the order of deposition: Massanutten Sandstone - Far right of diagram - Similar to today's Virginia Beach, but still in water over your head! Cub Sandstone (Cub SS) - Shallowed significantly to nearshore, streams feeding sediment into the basin Upper and Middle Martinsburg - All carbonate gone and deep water submarine landslides (Bouma Sequences) Lower Martinsburg - Deepest water - below all wave bases, begin mixing in material eroding from land Edinburg Formation - Still deeper, but still on the continental shelf Lincolnshire Formation - Deeper yet - between normal and storm wave base New Market Formation - Like wading in a bit deeper Beekmantown Formation - Like wading in on the Caribbean beach to water just over your head Conococheague Formation - Similar to a shallow white carbonate beach in today's Caribbean, except the only life on land is algal. The sequence of layers above is a typical "Highstand Systems Tract", a sea level cycle that begins with sea level at a low ebb. Relative sea level then rises until a point of "highstand" (deepest), after which it regresses and ends in a "sequence boundary". The top of this sequence boundary is formed after the Taconian Mountains are formed and have largely eroded away by the middle of the Devonian Period.

      Stromatolites-hamel... Gs _0639