5. Rember et al. (1993) measured the concentrations of 137Cs in the bottom sedim

Question

5. Rember et al. (1993) measured the concentrations of 137Cs in the bottom sediments of Medicine Lake, northern Idaho. Heavy-metal-laden tailings from the Coeur diAlene mining district were deposited in this lake. Tailings were deposited during floods as well-stratified, heavy-metal, contaminated silts on the lake bottom. Atmospheric testing of nuclear bombs, the source of 137Cs, began in 1951 and reached a maximum in 1964. 137Cs is first detected in the varved sediments at a depth of 30-32 cm and the 137Cs maximum occurs at a depth of 16-18 cm Calculate the average sedimentation rate for the varved sequence. The last layer of varved sediment is encountered at a depth of 10-12 cm. What is the age of this sediment layer? a. b.

Explanation / Answer

a)Answer: layer upper boundary difference= 30-16 = 14 cm in the range of 1951 to 1964 means in 13 years. Therefore, the rate of sedimentation is 1.077 cm/yr

b)Answer: Last layer upper boundary difference with the underlain layer is 16-10 cm = 6 cm. Considering the rate of sedimentation of 1.077 cm/yr, 6 cm layer will take time of 5.57 years. Hence, the age of the last layers is 1969 (Answer)

Related Questions

Navigate

• Browse (All)
• Browse 5
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.