Final answer:
The rock at +2.7 m depth cannot be definitively classified as either Paleogene or Cretaceous without additional geological context. The Cretaceous period is known for its chalk deposits and lasted from about 145 to 66 million years ago. Accurate dating would require examination of fossil content, mineral composition, and stratigraphic position.
Step-by-step explanation:
The question asks from which period a rock at +2.7 m depth is from, with the options being the Paleogene or Cretaceous period. To determine the age of rock layers, geologists often use index fossils which are organisms that existed only during specific time periods and had a wide geographical distribution. The Cretaceous is a geological period that spanned from about 145 to 66 million years ago (Ma) and is known for its chalk deposits, as reflected by its name derived from the Latin creta, meaning chalk. The rock at +2.7 m depth cannot be accurately identified as belonging to either the Paleogene or Cretaceous period without additional context such as the presence of specific index fossils or stratigraphy. However, considering the depth is relatively shallow, the rock could potentially be from either period depending on factors such as the rate of sedimentation and geological events in the area. Geologists would need to examine the rock for fossil content, mineral composition, and its position relative to other known geological layers to make an accurate determination.
When examining the distribution of fossils for the Himalaya Mountains, particularly near the Nepal/China border, using resources like the PaleoDB navigator can help identify during which two geologic time periods fossils were most abundant. Without access to the navigator, it's not possible to provide these specific time periods. Geologic maps and cross-sections like Figures 9.13 and 9.10 can provide insights into regional geological history. European geologists provided much of the initial mapping for regions such as the one described, using European names for geologic times like Lias and Dogger. In the region near Imilchil, sediment deposition during the Triassic period and subsequent deformation due to plate tectonics are key historical events.