Moose, yes, I am taking almost the standard YEC position.
Good quesiton about pre-flood rocks. The standard YEC stance would be created bedrock and then non-fossil containing layering from creation day 3 when the land emerged from the sea. My personal theology on this issue is that I tend to believe (although I'm not overly dogmatic on it) that the creation days were 1000 year days as discussed in 2 Pet and Psalms (in the context of creation and the flood). This sounds like day-age stuff but I believe it for theological reasons (1000y days obviously wont allow for evoltuion etc anyway).
The 1000 year days has a fascinating story behind it. Basically earth history can be conidered as a creative 'week' and a redemptive 'week'. The redemptive week is 7 1000 year days starting from 4000BC. We get 3 lots of 2000 year periods that align with Father, Son and Holy Spirit respectively. The 'father dispensation' begins with the father of all (Adam, 4000BC) to the father of 'all who believed' (as Abraham is called 2000BC). The 'son dispensation' begins with an only begotten son (Isaac, 2000BC) and ends with 'the' only begotten son (Christ, about 0 BC). The 'Holy Spirit' dispensation begins with the first 'outpouring' (Acts 2, 30AD) and ends, in this scenario, with the promised and in some opions begun 'last' outpouring of he Holy Spirit (about now). In Heb 4 'another' rest day like that of the creation week is described and this is clearly the Millenium = 1000y of Revelations. So in this scenario we could possibly, although non-dogmatically, expect the creation week to be 7000 years as well. This would give possibly enough time to generate the layers as the earth came up out of the sea on day 3. Standard YECs would probably insist this occured in a literal 24 hr day whereas my opinon would be that it occurred in a 1000 year 'day' as hinted at in Heb 4, Rev 22, Psalms and 2nd Pet. So that's a theological reason for having more time to create vast pre-flood sedimentry formations. It also has more important consequences for some Christians obviously. It's obviously hooey for a lot of other people of course.
You think our flood couldn't have generated the flood rock sediment? Mt St helen's demonstrated carving out of hard rock as well which suprsied me. I am satisfied that the flood, although instigated by God, occurred thourgh primarily actualistic means. The details are yet to be worked out, sure. God seems to have a habit of 'first the natural, then the sprititual' as my triune dispensational view of earth history (above) hints.