Question: what is marine mud ?

Christian Maerz answered on 18 Jun 2013:

Ooooh, don’t get me started! Marine mud is awesome! 🙂

It is a mixture of various things: Material that is weathered and eroded on land by rain, wind or ice, and washed into the ocean by rivers. The remains of organisms that were living in the ocean (shells, but also organic material). And, more exotically, minerals that form within the sediment due to chemical reactions. As long as this mixture is still soft and water-rich, we call it marine mud (or marine sediment). And usually, marine mud is very fine-grained, so nothing like sand or gravel. A lot like clay you use for pottery really. As soon as the mud gets harder (which happens if it is buried by new mud over time), we call it a mudstone.