ASBOG ASBOG - Association of State Boards of Geology Geochemistry and Soil Science Questions and Answers 2

Question 1

In geochemical exploration, what is the 'threshold' concentration?

Accepted Answer

The upper limit of background values above which concentrations are considered anomalous

Answer

The geochemical threshold is the statistically determined upper boundary of background values; sample concentrations exceeding this level are considered anomalies potentially indicating mineralization.

Question 2

The Unified Soil Classification System (USCS) uses two-letter symbols such as SP, ML, and CH. What does the first letter indicate?

Accepted Answer

Primary grain size group

Answer

In USCS, the first letter denotes the primary grain size group: G (gravel), S (sand), M (silt), C (clay), O (organic), or Pt (peat).

Question 3

Sandy soils have higher hydraulic conductivity than clay soils primarily because:

Accepted Answer

Sand has larger pore spaces allowing faster water flow

Answer

Larger inter-particle pore spaces in sandy soils offer less resistance to water movement, resulting in hydraulic conductivity orders of magnitude higher than fine-grained clay soils.

Question 4

Carbon-14 isotopic dating is effective for determining the age of groundwater up to approximately how many years?

Accepted Answer

40,000 years

Answer

With a half-life of approximately 5,730 years, carbon-14 is effective for dating groundwater and organic materials up to roughly 40,000 years before the present.

Question 5

What is diagenesis in the context of sediment geochemistry?

Accepted Answer

Physical and chemical changes in sediments after deposition but before metamorphism

Answer

Diagenesis encompasses compaction, cementation, dissolution, and recrystallization processes that convert loose sediment into sedimentary rock under relatively low temperature and pressure conditions.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG ASBOG - Association of State Boards of Geology Geochemistry and Soil Science Questions and Answers 2