The environments of particular deposits I came across this question in my text book:
&quot;During a visit to a mountainous area, students noticed a high mountain consists of 3 different parts: The top of the mountain consists of fossiliferous limestone. The middle of the mountain consists of fine grained rocks. The foot of the mountain consists of thick layers of boulder, gravel and tree trunks.
Which of those parts belongs to a marine environment? And which belongs to an aerobic environment? And which belongs to a river environment?&quot;
My attempt at a solution is this:

The top (fossiliferous limestone) -----&gt; marine environment.
The middle (fine grained rocks) -----&gt; aerobic environment.
The base (boulder, gravel and tree trunks -----&gt; River environment.

I wanted to know if my answer was correct or not, because the answer to the question in the book was:

the top---&gt; marine environment.
the middle---&gt; river environment.
the base --&gt; aerobic environment.

Could someone please clarify it for me?
Because the top layer is marine, you're being asked to think of the sequence being "coastal" in origin, where there is ocean, coastal plain, and inland mountains. In this scenario, two things are happening in tandem: the mountains are eroding and sea level is rising.

As the mountain erodes, boulders and cobbles (eroded from steep slopes) bury trees and form coarse conglomerates and source material for the coastal plain deposits, which are the middle unit of your sequence. As sea level rises due to local subsidence or a global sea level rise, the marine environment marches steadily inland depositing sands and then limestones.

Assuming no unconformities, yours is a textbook example of a continuous depositional sequence!