Loess in northern Pakistan? Current Understanding, Knowledge Gaps, and New Field Observations

Loess and other Late Quaternary palaeoclimate archives in Pakistan are not documented adequately yet and their extent and composition remain unclear, with only a few isolated occurrences being described. This highlights a major gap in systematic research to comprehend the ecological and palaeoclimate dynamics critical for the evolution of dryland and sedimentary records in this region. In this context the present investigation focuses on the presence and composition of silty Quaternary sediments. These have been suggested to be of aeolian and fluvial origin.

In this contribution, we summarize literature, and present observations from a recent field excursion supplemented by magnetic susceptibility data. We consider both aeolian loess and redeposited loess-like fluviolacustrine sediments to be present in much larger areas than earlier reports. Magnetic susceptibility properties are typical for in-situ sol formation, suggesting phases of landscape stability over at least centuries. We find that an aeolian sediment flux into the landscape was repeatedly intercalated by fluviolacustrine sediments of similar silt grain size. The aeolian sedimentation proceeded into mountain regions north of the Peshwar Basin, but in-situ preservation of fine material in sparse. At several places, loess is intercalated with (unrounded) slope deposits and fluvial deposits.

We conclude that Quaternary sedimentation in northern Pakistan is complex, and that landscape stability phases with soil formation occurred. Next steps will be to assess the stratigraphic and spatial (in) homogeneity of deposits, and to provide a temporal frame for soil formation phases.