| Popis: |
The field relationship of Lower Cretaceous sedimentary rocks to saprolite along the Fall Line provides new information about sedimentation and saprolite burial in Howard County, Maryland. The response that the saprolite, which was formed from a felsic gneiss, has made to the overlying sediment suggests that (1) the crystalline rock had weathered to saprolite before sediment emplacement, (2) the sediment was deposited by a highly erosive agent, (3) the saprolite was water saturated and deformed plastically during sedimentation, and (4) later reorientation of the sediment-saprolite deformation structures took place, probably during sediment compaction. Sedimentary petrology, sediment-saprolite contacts, and reverse density and injection structures along the sediment-saprolite boundary seem to rule out a Quaternary periglacial origin (congeliturbations) or any other origin involving saprolitization later than sedimentation. The field relationships and sedimentological analysis indicate synsedimentary deformation of the saprolite during Early Cretaceous time. |
