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The 40‐km‐long, Cobequid Bay—Salmon River estuary has a maximum tidal range of 16·3 m and experiences limited wave action. Sediment, which is derived primarily from areas seaward of the estuary, is accumulating faster than the high‐tide elevation is rising, and the system is progradational. The deposits consist of an axial belt of sands, which is flanked by mudflats and salt marshes in the inner half of the estuary where a funnel‐shaped geometry is developed, and by erosional or non‐depositional foreshores in the outer half where the system is confined by the valley walls. The axial sands are divisible into three facies zones: zone 1—elongate, tidal sand bars at the seaward end; zone 2—sand flats with a braided channel pattern; zone 3—the inner, single‐channel, tidal—fluvial transition. Tidal current speeds reach a maximum in zone 2, but grain sizes decrease headward (from medium and coarse sand in zone 1, to fine and very fine sand in zones 2 and 3) because the headward termination of the major flood channels prevents the coarse, traction population from entering the inner part of the estuary. Longitudinal progradation will produce a 20‐m‐thick, upward‐fining succession, the lower 1/2–2/3 of which will consist of cross‐bedded, medium to coarse sand deposited on the zone 1 sand bars. The ebb‐dominated portion of this unit will be finer grained than the flood‐dominated part, and will contain trough crossbedding produced by 3‐D megaripples; the flood‐dominated areas, by contrast, will consist mainly of compound cross‐bedding created by sandwaves with superimposed megaripples. Headward migration of swatchways (oblique channels that link the ebb‐ and flood‐dominated areas) will create packages of ebb cross‐bedding that is orientated at a high angle to the long axis of the estuary and that contains headwardinclined, lateral‐accretion surfaces. The overlying fine and very fine sands of zones 2 and 3 will be composed mainly of upper‐flow‐regime parallel lamination. The succession will be capped by a 4‐m‐thick unit of mixed flat, mudflat and salt marsh sediments. A review of other macrotidal estuaries with tidal ranges greater than 10 m suggests that the major elements of the model have general applicability.

A 3-dimensional (3-D) mapping investigation of Quaternary deposits in the southern part of the County of Simcoe is one of several 3-D mapping projects currently being undertaken as part of the Ontario Geological Survey's groundwater initiative within the Greater Golden Horseshoe area of southern Ontario. Following completion of these projects, a significant proportion of the most densely populated and fastest growing region of the country will be modelled in 3-dimensions, laying the foundation for regional syntheses of subsurface geology. The objective of this project is to develop an interactive 3-D model of Quaternary geology that can: 1) aid in studies involving groundwater extraction, protection and remediation; 2) assist with the development of policies surrounding land use and nutrient management; and 3) help to further understand the interaction between surface and ground waters. A better understanding of the geometry and inherent properties of the Quaternary sediments that overlie bedrock will assist with the development of revised source water protection plans and with the development of a geoscience-based management plan for the groundwater resource. Geoscience data collection was initiated in 2010 and consisted of detailed Quaternary mapping and sedimentological studies of the shallow subsurface, continuous coring to bedrock at 25 locations and a variety of geophysical surveys including: ground gravity, airborne time-domain electromagnetics, downhole geophysical logging and seismic reflection. Supplementary grain size, carbonate, heavy mineral and geochemical analyses enabled an improved interpretation of the subsurface stratigraphy. The information gained from this work resulted in a refined understanding of drift thickness and bedrock topography for the Laurentian trough area as well as the identification of 6 regionally significant chronostratigraphic units further subdivided into 15 layers. The main elements of the model, from youngest to oldest, include: 1) postglacial valley-fill deposits; 2) Oak Ridges Moraine (ORM) and equivalent deposits; 3) Newmarket Till; 4) Scarborough-Thorncliffe Formation equivalents; 5) non-glacial (Sangamon- Middle Wisconsin) deposits and 6) Illinoian and possibly older glacial deposits. Advancements in the understanding of the regional-scale architecture, contact relationships and depositional settings of these elements has allowed for an improved knowledge of the Quaternary history of the region. Notable observations include the identification of a widespread, non-glacial unit in the deep subsurface that likely spans the Sangamon to Middle Wisconsin time interval and the recognition of significant topographic relief of the Newmarket Till, extending from drumlinized uplands into broad valleys previously interpreted as tunnel valleys produced by the catastrophic release of subglacial meltwater. A protracted evolution for these valleys is currently being proposed. The character of groundwater flow within valley settings is more complex than observed in valleys underlying the ORM to the south. In Southern Simcoe County, the valleys are largely infilled with fine-grained units and upward hydraulic gradients commonly inhibit interaction of shallow with deep groundwater flow systems.

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Chavin de Huantar, a large pre-Inca temple complex in a steep-walled mountain valley, was constructed on three geomorphic elements: the toe of an inactive earthflow, an alluvial fan, and a river floodplain. Part of the temple complex suffered river-bank erosion early this century and structures indicate ancient Chavin inhabitants attempted to control river position. The temple complex and nearby valley floor was buried by a damaging debris flow in 1945. A nearby agricultural plain that likely influenced the siting of the temple complex represents an ancient landslide-dammed lake floor. The temple is constructed of large stone blocks, mostly sandstone and quartzite with lesser granite, limestone, and volcanic tuff. Sandstone and volcanic tuff could have been quarried locally but the nearest sources for limestone and granite are 3 km and 15 km from the site.

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