OUVER ET AL.: RELATIONSfflPS BETWEEN WAVE DISTURBANCE AND ZONATION 



CO 



SI5 



. (A) 



SlOH 



^ r- 



PERIOD 



71 



72 



73 



en 



2- 



71 



T^^ 



72 



YEARS 



73 



Figure 3. — Monthly wave periods (A) and heights (B) during 

 1971-73 at the Santa Cruz pier in northern Monterey Bay, Calif, 

 (means and ranges). 



ing the late fall and winter months. These obser- 

 vations are consistent with theoretical expecta- 

 tions (Komar 1976). 



Examination of the residue retained by the 0.5 

 mm mesh screen during the processing of vertical 

 strata from the long cores revealed additional 

 characteristics of the depositional environment. 

 At the 9 m station, strata below 25 cm contained 

 broken tests and spines of the sand dollar Den- 

 draster excentricus, broken mollusc shells, and 

 rounded, olive-green silt stones. The surface 

 stratum (top 25 cm) was homogenous fine sand 

 (Figure 2). Similar stratification was observed by 

 Howard and Reineck (1972) in the upper offshore 

 of a low-energy beach along Sapelo Island, Ga. 

 This concentration of shells and tests probably 

 resulted from physical winnowing or reworking 

 during severe storms. 



Long cores from 18 and 30 m had no shell/test 

 strata. Instead, there was a concentration of 

 woody chips of terrigenous, riverine origin and a 



VERTICAL STRATA (cm) 



05 5-10 10-15 15-20 20-30 30-40 



2000 



1000 







1000 



2000 

 50 





 50 

 50 





 50 

 50 





 50 

 50 





 50 

 50 





 50 

 50 





 50 



Pnonospio 

 cirnfera 

 I8m n = 9 



E 



if) 

 < 



Q 

 > 



Magelona 

 saccu/ata 



I8m n = 9 



Magelona 

 saccu/ata 

 30 m n = 5 



Mediomastus 

 callforniensis 

 I8m n = 9 



Mediomastus 

 ca/iforniensis 

 30m n = 5 



Scleroplax 

 granulata 

 I8m n=9 



Notomastus 



tenuis 

 I8m n=9 



Figure 4. — Vertical distribution of invertebrate species living 

 deep in the sediment in Monterey Bay, Calif, (mean per layer 

 based on n cores 50 cm long). 



high density of large oblong fecal pellets (1 mm 

 length) below 25-30 cm in the sediment (Figure 2). 

 The fecal pellets belonged to the deposit-feeding 

 capitellid polychaete Notomastus tenuis, which 

 lives deep in the sediment column (Figure 4). Al- 

 though fecal pellets were produced in situ, the 

 wood chips had been deposited on the surface and 

 were either buried by subsequent deposition or by 

 the biological reworking of the upper sediment 

 layers. Many large deposit feeders burrowed to a 

 depth of 20-30 cm (Figures 4, 5, 6). Nevertheless, 

 this deposit would not persist at the shallower 

 depths of stronger physical winnowing. 



In summary, surface ripple mark patterns, the 

 composition of deep sediment layers, frequent field 

 observations, and theoretical predictions indicate 

 a unidirectional gradient in substrate motion 

 highly dependent on depth. 



441 



