Final answer:
The statement about ammonite fossils indicating a desert environment is FALSE; they indicate an ancient ocean. Understanding fossil evidence, such as microbial mats from 3.5 billion years ago, helps us learn about Earth's history. Environments, where fossils are well-preserved, include deep-sea beds, swamps, and deltas, while deserts and rainforests are not conducive to fossil preservation.
Step-by-step explanation:
The statement that the abundant presence of ammonite fossils in a large area indicates that the area was once part of a desert is FALSE. Ammonites were marine animals, and their fossils suggest that the area was covered by an ocean in the past.
Fossils are the preserved remains or traces of organisms and provide important information about life in different geological time periods. For example, the fossil evidence of microbial mats indicates life existed about 3.5 billion years ago, helping us understand the environment of early Earth.
When considering what type of fossils one might find in different locations, it is important to understand the diversity of fossils through time, as well as the depositional environments that are best for preserving fossils. Sedimentary environments such as deep-sea beds, swamps, and river deltas, are suitable for fossil preservation due to their conditions that favor the rapid burial and low oxygen that reduce decay.
On the contrary, environments that are typically not suitable for preserving fossils are those with conditions that promote quick decomposition and erosion, such as deserts and rainforests. Sediment layers and the presence of certain fossils can signal significant events like mass extinctions. For example, fern spores found below the Cretaceous-Paleogene boundary but not above suggests a dramatic change in plant life, which is evidence of a mass extinction event.