Microfábricas de las arenicas del grupo Siwalik, sub-Himalaya de Nepal Central: Claves para cambios post-deposicionales

Abstract

Sandstones from the Siwalik Group of Central Nepal Sub-Himalaya were studied for microfabrics. Interlocking microfabric, packing microfabric, preferred orientation microfabric, authigenic microfabric and deformation microfabric were assessed in order to recostruct post-depositional changes in sandstones and understanding nature of intergranular volume reduction in sandstones. Sandstones from north belt (NB) are closely packed and are much consolidated, whereas sandstones from south belt (SB) are loosely packed  with weak grain contacts and strong cementing. Sandstones from NB were subjected to deep burial diagenesis, in which little initial cementation was followed by progressive compaction. Sandstones from SB underwent mechanical compaction followed by extensive carbonate cementation. Development of microfabrics and pore-reduction are due largely to compaction in sandstones from NB, but those in the sandstones from SB are due mainly to cementation and less to compaction.