POLLEN AND SPORES — LEOPOLD AND SCOTT 



313 



the presence of pollen and spores. Sandstones are usually barren, but 

 the absence of pollen from many coarse, aquatic sediments is thought 

 to be a derived condition. Modern lake sands that have been con- 

 tinuously wet since deposition often contain an abundance of well- 

 preserved pollen and spores, but lacustrine sandstones that have been 

 elevated and partially eroded usually contain none. Sediments having 



POLLEN 

 DENSITY 



LOG GRAINS 

 PER 



GRAM DRY 

 SEDIMENT 



50/gm 



10,000/gm 



25/gm 



:--" ; : : -- 



KAP1NGAMARANGI 



LAGOON 



SILTS 



I 



I 

 I 



PROBABLY 

 SLOW 



VARVED 

 CLAY 



(CONN ) 

 lOmm/varve 



5- 



0- 



7,000/gm 



1.000- 



100- 



LAKE CLAY 



(CONN) 

 SPRUCE ZONE A 



10- 



0- 



EAT 



LAKE P 



(CONN.) 

 PINE ZONE B 



I mm/year 



I mm/year 



RATE OF SEDIMENT ACCUMULATION 



Figure 5. — Pollen density in sediments compared with the rate of sediment accumulation. 

 Kapingamarangi lagoon sediments (left) are low in pollen, owing to poorly developed 

 local vegetation; the varved clay (second from left) is low in pollen because of dilution 

 of pollen rain by rapid sedimentation; the sediments in the two remaining examples (right) 

 arc rich in pollen because of dense contributing vegetation combined with a slow sedi- 

 mentation rate. 



