Hi,
I often see these referred to a "collapse layers" in English, but there may be another term.
I will provide references in a few minutes.
Karla

--------------------------------------------------
Note added at 42 mins (2009-02-04 17:23:37 GMT)
--------------------------------------------------

The following are academic references using the term:


...enabling access into the pit for the examination of the **collapse layer**.

http://www.cs.cmu.edu/afs/cs.cmu.edu/user/alavie/Grasp/temp/...

The initial stage of excavation went very slowly at first and involved the removal of humus and **collapse layer** above Stair A . After two days, in which only 10 non-descript body sherds were found in the screens, it was decided to forgo the half inch screening to visually screening until the excavation reached the architectural components. This initial clearing stage took a total of five days, working from the top down, and exposed a stairway in an advanced stage of decay.

http://74.6.239.67/search/cache?ei=UTF-8&p="collapse layer" ...

**collapse layer** had numerous burned clay and charcoal inclusions, but none of the charcoal was of sufficient diameter for tree-ring samples.

http://yellowjacket.colorado.edu/5MT3_report.pdf

extensive **collapse layer** that covered most of the church above floor level (plates 2–3)

http://www.nyu.edu/isaw/amheida/inc/pdf/Report2007AG.pdf