Final answer:
No, water is not necessarily present in the formation of all rock types. Water is crucial for the formation of sedimentary rocks, as it transports and deposits sediments. Banded iron formations provide evidence of early photosynthetic life and oxygen levels, and fine-grained sediments are better at preserving fossil impressions than coarse-grained.
Step-by-step explanation:
Is water present in the process of formation of sedimentary rocks? No, not all types of rocks require the presence of water for their formation. For instance, igneous rocks are formed from the cooling and solidification of magma or lava, and metamorphic rocks are created through the alteration of existing rocks under the influence of high temperature and pressure, which may or may not involve water. However, water can play a vital role in the formation of sedimentary rocks by transporting and depositing sediments, as well as facilitating chemical reactions.
Regarding the question of how the banded iron formations shed light on early Earth conditions, it is important to note that these formations exhibit alternating layers of iron-rich and iron-poor material. The presence of hematite and magnetite suggests that there was dissolved oxygen in the water, hinting at the early emergence of photosynthetic organisms, which could have contributed to the oxygen levels. The alternating bands signal changes in the environmental conditions over time, providing insights into the cycles of the early Earth's atmosphere and hydrosphere.
The grain size of the surrounding rock and the potential to preserve impressions in coarse-grained sediment are influenced by the conditions of sediment deposition and lithification. Fine-grained sediments such as clay can capture and preserve delicate impressions better than coarse-grained sediments like sandstone due to the smaller particle size and their ability to compact closely together.