Geoffrey W. Smith

Quaternary glacial history of Mount Olympus, Greece

Erosional and depositional evidence on Mount Olympus, Greece, and across the adjacent piedmont provides clear indication that the mountain was more extensively glaciated over a longer period of time than has been previously reported. The stratigraphic record of Pleistocene–Holocene events on Mount Olympus is most clearly documented on the eastern piedmont, where three discrete sedimentary packages (units 1–3), each capped by a distinctive soil, reflect glacial and nonglacial activity in the Mount Olympus region. A working stratigraphic framework for sediments and soils is proposed and is tentatively correlated with a dated alluvial succession south of Mount Olympus. We suggest that the oldest sedimentary package (unit 1) predates 200 ka (isotope stage 8?). Lithologic and pedologic equivalents of the piedmont stratigraphy are found within major valleys draining Mount Olympus, as well as within cirque basins and on the summit plateau surface. These deposits can be clearly tied to three stages of cirque development on the upland and at valley heads. Taken together, upland and piedmont glacial features and deposits indicate the following general scenario: (1) earliest glaciation (isotope stage 8?) produced upland ice and valley glaciers that extended as piedmont lobes east, north, and west of Mount Olympus; (2) nonglacial (interglacial) conditions (isotope stage 7?) were accompanied by extensive erosion and subsequent pedogenesis; (3) a second glaciation (isotope stage 6?) involved production of upland ice and valley glaciers that did not reach the piedmont; (4) interglacial (interstadial) conditions (isotope stage 5?) provided time for stream erosion and substantial pedogenesis; (5) final(?) glaciation (isotope stages 4–2?) was restricted to valley heads (no upland ice) and glaciers that extended to mid-valley positions; (6) nonglacial conditions (isotope stage 1?) were associated with additional pedogenesis and stream incision. The largest cirque on the mountain (Megali Kazania) may contain depositional evidence for neoglaciation. Study of the neotectonic history of the Mount Olympus region indicates that uplift has persisted throughout the mid-Pleistocene and Holocene at a rate of about 1.6 m/k.y.; the total uplift since deposition of unit 2 is approximately 200 m.

Facies architecture and grounding-line fan processes of morainal banks during the deglaciation of Coastal Maine

Submarine jet processes are inferred from glaciomarine facies exposed in gravel pits in southwestern coastal Maine. The geometry and distribution of fan facies depend on (1) the proximity to the grounding line and stream effluxes, (2) the angle of jet trajectory from glacier conduits, and (3) sediment remobilization processes. Syndepositional glaciotectonic deformation further augments morainal bank formation through pushing and squeezing of fan sediments at the grounding line. Complex process-sediment interactions along the temperate tidewater margin of the Laurentide ice sheet are recorded in the facies architecture of sedimentary sequences in morainal banks. Morainal bank accumulation was governed by rapid fluvial deposition, and outwash jet dynamics that controlled the spatial distribution of sedimentary facies. Near the grounding line, meltwater dynamics change rapidly where sediment-laden fresh water is discharged at or near the sea floor. Turbulent mixing with ambient sea water and discharge fluctuations cause rapid changes in flow competence, accompanied by the dumping of bed-load gravel and sand at the apices of grounding-line fans in the morainal banks. Jet trajectory relative to the morainal-bank slope determines whether a jet will make contact with the morainal bank. Gravel and sand remain in bed-load traction as long as the jet is in contact with the morainal bank. Bed-load dumping and settling of the coarse suspended load occurs where buoyant forces in the jet overcome momentum forces or where the jet is deflected by the morainal bank. Below these buoyant jets, backflow eddies can produce currents that drive ripple migration toward the grounding line. Abrupt facies changes record fluctuations in jet discharge and trajectory and sediment redistribution by sediment gravity flows initiated near the grounding line.

Kennebunk glacial advance: A reappraisal

Evidence for the Kennebunk glacial advance (readvance) in southwestern Maine is discussed in light of recent geologic mapping. Orientations of glacially produced lineations record the response of ice to major topographic controls and do not indicate glacial readvance. Minor end moraines and large stratified end moraines associated with deformed marine sediments of the Presumpscot Formation occur throughout the southwestern coastal zone. These features outline the general pattern of ice retreat from this part of the coastal zone and suggest that withdrawal of the last ice from southwestern Maine occurred with minor stillstands and local frontal fluctuations but without significant readvance. The Kennebunk glacial advance (readvance) appears to have been one of many local fluctuations of the ice front during general recession, occurring at about 13,200 yr B.P.