I. Geologic Problems in the Mediterranean Sea

A.  faunal "crisis" ~ 5 Ma - Late Miocene Epoch
 
 

 1.  v. low diversity -
 
 

 2.  v. low abundance -
 
 

  B. thick evaporite deposits around Med.

 1.  calcite, gypsum, halite, others from salt water
 
 
 

 2.  modern evaporites (sabhkas, salt pans)
 
 
 
 
 

C. 1km deep Rhone River gorge in S. France buried beneath the current river
 
 
 
 
 
D. Strong Seismic Reflector (read about seismic data at end of Chap 4)
- represents a widespread rock layer of uncertain origin...

 II.  Deep Sea Drilling Project

  A.  Sent Glomar Challenger drillship in 1970

 1. Mediterranean is deep water!   >2km deep
 
 
 
 
 

 2.  Drill holes, take core samples.
 
 
 
 

  B.  Drilled several wells and found:

 1. post-Miocene deep water sediments
 
 

  2. gypsum, desiccation cracks
 

 3. tiny bit of halite in the deepest hole
 

 4. did not drill below halite bed.
 

   C. Mediterranean Dry!  Controversy erupted!

1.  11 scientists said Med was shallow until "salinity crisis" then deepened:
 Reflux model for evaporites - barred basin
 
 
 
 
 
 
 
 
 

 2.  3 scientists suggested Med was deep, then dried up like Death Valley
  a. Evaporative drawdown model - dessicated basin
 
 
 
 
 
 
 
 
 
 
 

  b. explains Rhone River gorge
 

  c. how to test this?
 
 

   D. Aftermath, many convinced, many not.

 1.So, then more evidence found:

  a.  more river gorges found (Nile, etc.)
 
 
 
 

  b.  karst topography developed in Yugoslavia
 
 
 
 

  c.  today's fauna similar to Pliocene, not Miocene
 
 
 
 

  d.  plant communities changed to more arid types
 
 
 
 

 E.  Test the hypothesis!  2nd DSDP cruise in 1975

  a. found more salt (widespread)
 
 
 

  b. found deep water sediment below salt
 
 
 

- now 10 of 12 "believed" in the dried up Med Sea.
 
 

F.  Other Evaporite Giants:

  a. Gulf of Mexico
 
 
 
 
 

  b. early (narrow) North Atlantic.