All stations showed an apparent grain size major mode of > 

 4 phi (silt-clay) with subordinate sand modes ranging from very coarse 

 to very fine sands (-1 to 3 phi) . Since the January 1984 survey, fine 

 sand (3-2 phi) has dominated the surface texture of station Center. 

 This sand layer has been interpreted to represent a lag deposit 

 resulting from washing of fines from the apex of the mound. In the 

 October 1985 survey, fine sand layers were also found to be developing 

 at stations 150E and 100W. It was suggested that this was caused by 

 Hurricane Gloria. These stations have continued to show sandy 

 surfaces and, in addition, all other FVP stations showed a sand 

 component in the near surface sediment (Figure 3-19) . 



Some of the sand-sized particles were apparently biogenic 

 (foraminiferal tests and molluscan shells) and may represent the 

 gradual accumulation of skeletal material as successive populations 

 contribute their hard parts to the sedimentary matrix. The sand 

 fraction in other cases consisted of mineral grains. It is possible 

 that the sand fraction of the near-surface sediment increased due to 

 the onshore to offshore transport of sand related to Hurricane Gloria. 

 This inference is based on the presence of a 9 cm thick, fine sand 

 (3-2 phi) layer overlying silt clay at a station located in 50 feet 

 of water approximately 4000 m north-west of the FVP area (SAIC, 

 1989a) . 



In June 1985, approximately 80% of the FVP photographs 

 showed the widespread presence of reduced mud at the sediment surface 

 including the mound, flanks, and ambient bottom. Reduced sediment at 

 the surface was not seen at the CLIS reference station. The origin 

 of this reduced sediment was attributed to surface erosion of the FVP 

 mound and the local redistribution of Black Rock Harbor muds. In 

 October 1985 (post-Hurricane Gloria) , about 50% of the photographs 

 showed reduced sediment at the surface. Two of the 20 CLIS reference 

 photographs in October also showed reduced sediment at the sediment- 

 water interface. In the 1985 case, the effects of Hurricane Gloria 

 were suggested to be the agent eroding the top 2-3 cm of oxidized, 

 biogenically-reworked upper sediment. In this survey, only one 

 replicate at station 500W showed reduced mud clasts at the sediment 

 surface; it is possible that this was an artifact introduced by the 

 REMOTS® prism window wiper. Reduced sediment was not seen at the 

 sediment-water interface in any of the photographs from the new CLIS 

 reference station. In this survey, there was little or no evidence 

 of exposure of the reduced Black Rock Harbor muds to the water column. 



The frequency distributions of boundary roughness values 

 for the dredged material mound, edge and ambient stations, and the 

 new CLIS reference station were all similar, with the major mode for 

 small-scale topographic relief at the 0.8 cm class interval (Figure 

 3-20) . These boundary roughness values were not significantly 

 different from those measured in October 1985. However, both the 

 October 1985 and July 1986 boundary roughness values were 



11 



