Question

1. a paleontologist is studying a cross - section of sedimentary rock layers in a canyon wall. the layers are labeled (from bottom to top) as follows: • layer 1: contains trilobite fossils • layer 2: contains a volcanic ash layer with a known radiometric age of 280 million years • layer 3: contains ammonite fossils • layer 4: tilted and folded rock layer • intrusion a: igneous rock cutting through layers 1 - 3 but not layer 4. based on this information, which conclusion is best supported by relative dating principles and fossil evidence? the trilobites in layer 1 are older than the ammonites in layer 3 based on the law of superposition and faunal succession. the folding of layer 4 occurred before the deposition of layer 1. intrusion a is older than layer 1 because it is found beneath layer 4. the radiometric date of 280 million years applies to all layers above and below the ash layer.

Explanation:

The law of superposition states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest are at the top. Faunal succession helps in dating rocks based on the fossils they contain. Trilobites are older fossils compared to ammonites. Layer 1 is below Layer 3, so trilobites in Layer 1 are older than ammonites in Layer 3. Layer 4 is tilted and folded, and intrusion A cuts through Layers 1 - 3 but not Layer 4, indicating Layer 4 is older than intrusion A and Layers 1 - 3 are younger than Layer 4. The radiometric age of the volcanic ash in Layer 2 only applies to that layer and not others.

Answer:

The trilobites in Layer 1 are older than the ammonites in Layer 3 based on the law of superposition and faunal succession.