Geologists? Help me with Appalachian Mountains and the Coal Fields

[JoeSchmuckatelli]

As I understand it, the Appalachian mountains are among the oldest on earth - 1.2 billion years old.  Formed when Gondwanaland was a thing.  Supposedly taller in their day than the Himalayan range of today.  Results of proto continent collisions. We only see the weathered remains of the mountains. 

Coal, as I understand it, is the remnants of forests formed during the carboniferous period - the biological arms race had produced lignin in plants that fungi and bacteria had yet learned to digest.  Over millions of years the trees died, laying undigested and forming peat bogs and covered by water and sediments (shallow seas/lakes) eventually, coal.   The bands were generally horizontal until the separation of the NA continent building process folded up the land and coal bands. 

Here is the problem I'm having: the mountain building predates the carboniferous.  And yet the coal bands are in the Appalachian range. 

How? 

Sources appreciated!

[Piscator]

According to Wikipedia there seem to have been at least four distinct periods of mountain-building (and subsequent erosion). So while some of the rock formations are indeed over a billion years old, the process that created the actual mountains (as in something that can be seen rising above the surrounding area) happend only some tens of millions of years ago. At least, that's how I understand it from my casual read.

[kerbiloid]

https://en.wikipedia.org/wiki/Geology_of_the_Appalachians#Geological_history

Quote

Overview

The Appalachian Mountains formed through a series of mountain-building events over the last 1.2 billion years:[4][5]

    The Grenville orogeny began 1250 million years ago (Ma) and lasted for 270 million years.
    The Taconic orogeny began 450 Ma and lasted for 10 million years.
    The Acadian orogeny began 375 Ma and lasted 50 million years.
    The Alleghanian orogeny began 325 Ma and lasted 65 million years.

1.2 bln ya it was just a project start.

Real mountain building was just 400 mln ya.

[farmerben]

Still the Appalachians were high altitude unlike the shallow seas at the Illinois and Wyoming basins.  The Appalachian coal is in thinner seams of anthracite coal, whereas the latter two basins are bituminous and much thicker.

[Terwin]

High altitude may be less of a problem for plants when the earth is not in an ice age(remember: ice caps, glaciers, and year-round snow covered mountains is very much not the norm in geologic history) and higher carbon in the atmosphere helps plants survive in much less favorable environments, such as during the Carboniferous periods.  

[kerbiloid]

Btw, did the fern woods grow on mountains?

I mean, they are cursed to need much water.

[farmerben]