Sampling and Size Distribution of Quartzose Pebbles from Three New Jersey Gravels

Abstract

Measurement of 3,600 quartzose pebbles from six gravel outcrops, representing fluvial, beach, and glacial deposits in New Jersey, yields the following results. Size distributions of long, axis measurements show that samples of beach pebbles have the largest mean size, $$-4.207 \phi$$, and a standard deviation of $$0.6190 \phi$$, while glacial pebbles have the smallest mean size, $$-3.796 \phi$$, and the largest standard deviation, $$0.6216 \phi$$. Fluvial pebbles have a mean size of $$-3.970 \phi$$ and the smallest standard deviation, $$0.4960 \phi$$. Statistical tests of three types of sampling plans-sedimentational unit, channel, and random grid-executed at each outcrop demonstrate that sedimentational unit sampling is most appropriate for well-layered deposits such as stratified drift or bedded beach gravel. Channel sampling is most efficient for homogenized deposits such as glacial till, and random grid sampling is most reliable for massively bedded deposits.