Nice looking unit.
Looking at the specs, and looking at https://kenrockwell.com/audio/zoom/h4n.htm you should be able to record anything down to 30-ish Hz, and up to at least 22 kHz, but possibly you might want to do some post-processing to level between about 2 kHz and 10 kHz.
In WAV mode you can sample up to 96 kHz -- though it is not immediately clear to me that the mics can retain their sensitivity between 22.05 kHz and 44.1 kHz . That range is pretty much in ultrasound, and ultrasound typically needs specialized mics to record properly.
The main drawback I can see at the moment is that the microphones are not well protected, and if you are going to put them very close to where you are hitting rocks, which might chip, then you could get rock chips flying in that might be a problem.
