A HIGH-RESOLUTION RECORD OF ADVANCE/RETREAT PHASE GLACIMARINE SEDIMENTS: IMPLICATIONS IN RECONSTRUCTING GLACIAL DYNAMICS

The accurate analysis of the glacimarine sedimentary record is critical when reconstructing past glacial dynamics. Seismic reflection data, sea floor morphologies, and core records are commonly used in high-latitude continental margins to characterize modern and past depositional environments and infer periods of glacier retreat and advance. Seismic reflection data are especially critical when characterizing a temperate glacimarine environment because of high rates of sediment accumulation and the heterogeneity of the strata. Here we characterize the modern depositional environment of Disenchantment Bay using two high resolution seismic reflection data sets, chirp data, and core data. This analysis is unique in that Hubbard Glacier has been advancing within Disenchantment Bay since at least the 1890s, which provides an opportunity to examine both advance and retreat phase sediments. Of particular interest is the lateral and vertical heterogeneity of the strata inferred from the seismic data, which may impede core correlation. Our results show that the formation of temperate glacimarine varves within the bay is vertically limited and appears to be a result of deposition over the past 10s of years. Varve heterogeneity is apparent and is inferred to be a product of localized erosion and deposition from minor sediment gravity flows. Chaotic acoustic facies at depth are attributed to larger-scale sediment gravity flow deposition and are interpreted to represent remobilized grounding line material deposited during glacial retreat or during periods of renewed glacial advance with localized ice extension. Basal surfaces of the interpreted debris flows within the ultra-high resolution seismic profiles show erosional truncation, yet such sequences are shown to be conformable in a lower resolution profile. Such features warrant caution when interpreting similar stratal truncations as subglacial erosion surfaces, which could result in an erroneous interpretation of ice dynamics.