330 



HEEZEN AND LAUGHTON 



[chap. 14 



where gradients as low as 1 : 7000 have been measured (Fig. 13). The floor of 

 the Gulf of Mexico is dominated by the Mississippi Cone, which has not only 

 supplied sediments to the Sigsbee Abyssal Plain, but also to the smaller abyssal 

 plain of the eastern gulf, which extends along the base of the West Florida 

 EscaqDment into the Campeche Tongue. 



Sedimentation related to the building of individual distributory channels 

 and fans of the Mississippi Cone has built this feature completely across the gulf 

 floor to the base of the Campeche Escarpment, cutting the gulf floor into two 



• Cores 



50 Fathom Contours 



10 Fattiom Contours 



I Fattiom Contour 



Contours by Bruce C Heezen 



Halambia Iniorraitg 



LAMONT CCOl-OOICAl- OBSERVATORY 



Ectio sounding ot 800 fm/sec 

 with Precision Deptti Recorder 

 ■^^ Scarps and hills 



Fig. 13. Bathymetric chart of the Sigsbee Abyssal Plain. (After Ewing, Erieson and 

 Heezen, 1958.) 



halves. A small apron of sediment s^ireads out a few miles from the base of the 

 Campeche Escarpment. The Sigsbee Abyssal Plain is probably fed in part by 

 canyons leading from the east coast of Central Mexico and out of the Bay 

 of Campeche (Ewing, Erieson and Heezen, 1958). 



Over 10 m of fine silt was deposited on the Sigsbee Abyssal Plain during 

 Wisconsin time (Ewing et al., 1958). Rates of sedimentation exceeded 60 cm/ 

 1000 years during the Wisconsin but have averaged less than 8 cm/ 1000 years 

 in Recent time. A number of small topographic prominences of about 6 fm 



