Continental Margins Flashcards
continental margins
drowned edges of continents
what are the physiographic provinces of a continental margin?
shelf, slope, rise
how are continental margins classified?
by passive and active margins
passive margins
‘atlantic type’, long history of sedimentation, margin subsides, tectonism is less important
how is sedimentation on passive margins?
margin accumulates sediment and progrades seaward
active margins
‘pacific type’, tectonism is convergence, deformed sediments, uplift and compression
how is sedimentation on active margins?
sediments are deformed, forming accretionary prisms from erosion of volcanic material or by bottom currents
which type of margin has more earthquakes?
active, pacific type
which type or margin has a flatter-lying strata?
pacific, atlantic type
which type of margin is narrower?
active, pacific type
which type of margin typically has mountains associated with it?
active, pacific type
which type of margin is more closely associated with a plate boundary?
active, pacific type
what is the distribution of lithogenic sediments on continental margins?
distribution is based on energy: high energy, coarse-grained sediments and low energy, fine-grained sediments. reworked and winnowed by sea-level changes; relict sediments
shelf sediments
average grain size reflects the energy of the depositional environment
what are factors controlling grain size on the continental shelf?
shoreline turbulence, shore-parallel currents, grain size decreases seaward for recent sediments, past fluctuations of sea level (relict sediment)
relict sediment
remnants of past environmental conditions that were deposited during periods when sea levels were lower; mostly coarse-grained
winnow
natural removal of fine sediment particles from a coarser sediment deposited by wind or flowing water
what is the distribution of biogenic sediments on continental margins?
different species, different places: temp, salinity and depth, turbulence (energy), turbidity (water clarity), environmental indicators.
