Monday, November 1, 2010

Estuarine Sediment Grain Size Determination

Marine geologists analyze sediment grain sizes to understand the composition of earth within a survey site. Through this analysis, they can predict sediment composition changes when the information is combined with other datasets (weather, land use). On September 20, 2010, the research methods class conducted an estuarine sediment grain analysis exercise.

Sediment cores collected from a previous survey (blog post 9-10-10) were procured for this exercise. A stacked series of cylindrical mesh sieves and water were used to manually separate the sediment grains according to the following sizes:

Coarse sand -1000 µm
Medium sand - 250 µm
Fine sand - 125 µm

The contents of each sieve were rinsed with water before they were transferred into pre-weighed collection dishes and dried in a laboratory oven for 7 days. The samples were weighed after drying.

The Station A core had a calculated dry weight of 8.41 g. Coarse sand was in 2.26 g (27%) of the sample. 3.06 g (36%) of the core was medium sand. 3.09 g (37%) of the core consisted of fine sand (Figure 1; Table 1).

The Station C core had a calculated dry weight of 62.13 g. Coarse sand constituted 14.57 g (23%) of the sample. 9.32 g (15%) of the core was medium sand. 38.24 g (62%) of the core consisted of fine sand (Figure 1; Table 1).

The Control core had a calculated dry weight of 82.36 g. Coarse sand was in 2.11 g (3%) of the sample. 10.66 g (13%) of the core was medium sand. 69.59 g (84%) of the core consisted of fine sand (Figure 1; Table 1).
Figure 1 - Estuarine sediment grain size to weight composition. 
Skidaway Island, GA

  
Table 1 - Dry sediment weight of sieved samples.  Skidaway Island, GA.


Station A
Station C
Control
Coarse sand
1000 µm
2.26 g
14.57 g
2.11 g
Medium sand
250 µm
3.06 g
9.32 g
10.66 g
Fine sand
125 µm
3.09 g
38.24 g
69.59 g
Total weight
8.41 g
62.13 g
82.36 g



In conclusion, the sediment cores in this exercise contained high quantities of fine and medium grain sand.

A plausible theory: This area experiences high tide differentials (8 feet / 2.4 meters twice daily); yet the energy of the water as it enters and leaves the study site is low. As a result, sediment grains of smaller size are able to settle and accumulate since the water is flowing at a relatively steady rate.

2 comments:

  1. Research Lab researchers is the top favorite. Researchers working on so many projects and producing good results.Custom quartz parts

    ReplyDelete
    Replies
    1. Amazing!I also wish him good luck to defend his gold medal. I like to share it with all my friends and hope they will also encourage him.
      link - http://cbloomensteinchemistry.blogspot.in/2011/12/sodium-silicate-polymer-lab.html

      Delete