Late Quaternary Marine Geology of Makkovik Bay, Labrador

Abstract
Makkovik Bay is a low relief, 35 km long, complex fiord on the central Labrador coast. Jt is a well stratified, partially mixed-type estuary during the summer, probably with moderate sea water exchange. The degree of stratification appears to be related to fluvial flux and tidal mixing and is attenuated by sills and mid-fiord constrictions. Low values of suspended sediment and high rates of sediment accumulation measured by sediment traps suggest that the contemporary environment is wave-dominated, resuspending marginal sediments with deposition in the deeper basins. Three major surficial units are recognizable within Makkovik Bay as interpreted from 3.5 kHz acoustic analogue data: lower basin-fill, conformable cover and upper basin-fill units. The lower basin-fill unit underlies the conformable cover unit in the deeper, quieter basins and is thought to be composed of coarse proglacial delta sediments, probably deposited prior to 11 000 years B.P. The conformable cover unit is acoustically well stratified and mantles the en tire bay, outcropping along topographic highs and in the nearshore zone. Short cores and grab samples penetrate an upper zone of stiff, homogeneous, olive-grey clayey silt and a lower zone of alternating brownish-grey and olive-grey beds with thin basal silt laminae. The distribution of benthonic foraminifera suggests a high rate of sedimentation in an open bay environment. The conformable cover unit is interpreted to have had runoff-dominated deposition from suspension occurring during the last major transgression terminating at approximately 10 000 years B. P. Glacial detritus was transported fluvially northwards along the Makkovik Brook and nearby valleys and distributed across Makkovik Bay within the upper fresher water layer of a well stratified two-layer type estuary. Rapid de position occurred through the lower, more saline water layer. The upper basin-fill unit is characterized by poor acoustic reflectivity and a ponded depositional style with a variable degree of onlap which is inversely related to wave energy. Two piston cores penetrate four major facies of the upper basin-fill unit that represent a transition from runoff

This publication has 0 references indexed in Scilit: