Determine the placement of the Carboniferous– Permian boundary in the deep-water

Question

Determine the placement of the Carboniferous– Permian boundary in the deep-water Usolka River section using stratigraphic occurrences of key conodont species.

Determine the radiometric age of the Carboniferous-Permian boundary by integrating radiometric dates derived from ash beds (bentonites) with the conodontdata derived from marine limestones.

1. The list below shows the occurrences of key conodont species in the Usolka River section. Using this data, plot the ranges of all conodont species on figure 2.3. Ranges of S. bellus, S. pawhuskaensis, and S. brownvillensis have already been done by way of example.

Sample 13 S. bellus, S. pawhuskaensis

Sample 15/1 S. pawhuskaensis, S. brownvillensis

Sample 16/1 S. brownvillensis, S. simplex

Sample 16/2 S. brownvillensis

Sample 16/3 S. simplex, S. wabaunsensis

Sample 16/4 S. wabaunsensis

Sample 16/5 S. wabaunsensis, S. isolatus

Sample 16/6 S. wabaunsensis, S. isolatus, S. cristellaris, S. longissimus

Sample 16/7 S. cristellaris

Sample 18/1 S. longissimus, S. constrictus

Sample 20 S. longissimus, S. barskovi

Sample 21 S. constrictus, S. barskovi

Explanation / Answer

From the given example and the given data the plots can be made as follows:

Bellus = 13. So mark a point at 13

S.pawhuskaensis = 13 to 15/1 So mark a line from 13 to 15/1 as 13 - a-b-14-c-d-e-15/1

S.brownvillensis = 15/1 to 16/2 So mark a line from 15/1 to 16/2 as 15/1 - 16/1 -16/2

S.simplex = 16/1 to 16/3.So mark a line from 16/1 to 16/3 as 16/1 - 16/2 - 16/3

S.wabaun sensis = 16/3 to 16/6 .So mark a line from 16/3 to 16/6 as 16/3 - 16/4 - 16/5 - 16/6

S.isolatus = 16/5 to 16/6 .So mark a line from 16/5 to 16/6 as 16/5- 16/6

S.cristellaris = 16/6 to 16/7.So mark a line from 16/6 to 16/7 as 16/6 - 16/7

S.longissimus = 16/6 to 18/1.So mark a line from 16/6 to 18/1 as 16/6 - 16/7 - 18/1

S.constrictus = 18/1 to 21.so mark a line from 18/1 to 21 as 18/1 - 20 - 21

S.barskovi = 20 to 21 .so mark a line from 20 to 21 as 20-21

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