scholarly journals Neogene Calcareous Nannofossils from the Mediterranean—Leg 42A of the Deep Sea Drilling Project

Author(s):  
C. Muller
1977 ◽  
Vol 14 (4) ◽  
pp. 707-715 ◽  
Author(s):  
Robert C. Howe ◽  
C. Howard Ellis

During Leg 37, Deep Sea Drilling Project, several holes were drilled on the northwest flank of the Mid-Atlantic Ridge. Calcareous nannofossils can be used to define age limits for the upper portion of basement rocks at sites 332 and 334. Nannofossil oozes recovered from immediately above basement basalts in holes 332A and 332B are of early Late or late Early Pliocene age (Discoaster tamalis or D. asymmetricus Subzone). Nannofossil chalks recovered from as deep as 180 m below the top of basalt in these holes are of late Early Pliocene age (D. asymmetricus Subzone). Nannofossils recovered from sediments immediately overlying basement basalts in hole 334 are of early Late Miocene age (D. bellus Subzone). Nannofossil chalks recovered from 50 m below the top of basalt in this hole are of late Middle Miocene age (Catinaster calyculus Subzone). Nannofossils recovered from the calcareous matrix of a gabbro and periodotite breccia occurring 68 m below the top of the basalt are also of late Middle Miocene age (C. coalitus Zone).The results indicate that the upper 180 m of basalt at site 332 were formed during an interval of time not exceeding 1 million years. At site 334 the upper 50 m of basement basalts were formed during an interval of time not exceeding 4.5 million years.


1989 ◽  
Vol 63 (1) ◽  
pp. 10-14 ◽  
Author(s):  
Wuchang Wei ◽  
Sherwood W. Wise

An investigation of middle Eocene calcareous nannofossils from Deep Sea Drilling Project Sites 162 and 361 has revealed a new species, Discoaster praebifax, and prompted the emendation of Discoaster bifax Bukry. Based on their morphologic similarities and stratigraphic relationship, D. praebifax is suggested to be the ancestor of D. bifax. Because the new species closely resembles D. bifax, the use of the latter as an index species for Subzone CP14a should be cautioned. The first occurrence of D. praebifax is, however, a potentially useful datum in Zone CP12.


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