Multi-Proxy Records of Late Holocene Flood Events From the Lower Reaches of the Narmada River, Western India

Analyses of a fluvial sedimentary sequence from the lower reaches of the Narmada River establish a record of rhythmic cycles of sediment facies that represent floods during the late Holocene. The south-west Indian monsoon strongly influences the study area, and heavy rainfall or cyclones which originate from either the Bay of Bengal or the Arabian Sea, also affect the region. Optically stimulated luminescence dating places the 8 m thick sediment sequence in the climate transition phase which ranges from the Medieval Warm Period to the Little Ice Age. Multi-proxy analyses including high-resolution granulometry, magnetic susceptibility, ferromagnetic mineral concentration, facies major oxide geochemistry, and micro-fossil records (from two sedimentary units) are used to study these late Holocene flood events. The latter are characterised by multiple sediment facies, depositional events, changes in channel morphology, and distinctive flood signatures. Integration of these records enables to identify two distinct aggradations viz. phase I and phase II, as well as a relative change in channel morphology. The study describes 11 flooding events and their imprints over multi-proxy records. Historic documents and instrumental records from the town of Bharuch referring to floods, movement of channel sand, channel shallowing, and the dysfunction of the ancient port of Bharuch further validate the inferences drawn from the sedimentary sequence. The study exemplifies the need to use high resolution and multi-proxy studies to interpret paleoflood records and climate signatures in order to build archives of monsoonal rivers.

Automated summary

Analyses of a sedimentary sequence from the Narmada River in southwest India reveal rhythmic cycles of sediment facies representing floods during the late Holocene, influenced by the Indian monsoon and cyclones from the Bay of Bengal or Arabian Sea. Optically stimulated luminescence dating places the sequence in a climate transition phase between the Medieval Warm Period and Little Ice Age, and multi-proxy studies are used to study late Holocene flood events. Integration of sediment records with historic and instrumental data validates the findings and emphasizes the importance of high resolution multi-proxy studies for interpreting paleoflood records and climate signatures.