Carbonate and evaporite sedimentation at Clinton Lake, British Columbia, Canada

Abstract

Clinton Lake is a small ephemeral lake lying in a glacial paleomeltwater chan nel near Clinton, Interior British Columbia. The lake is a M g-N a-S04 brine (>300 g I-1 TDS), similar to those at Basque, 50 km to the south. Like the Basque Lakes, Clinton Lake has permanent deposits of epsomite.There are six main depositional subenvironments: (1) hillslopes, (2) springs, (3) carbonate playa, (4) hummocky carbonate mudflats, (5) saline mudflats, and (6) ephemeral lake or saline pan. There is no channelled inflow, and Clinton Lake is fed mainly by groundwater, direct precipitation, and diffuse runoff. About 120 m north of the lake, at slightly higher elevation, lies a small carbonate playa, called Clinton Pond. This is fed by a series of small springs and seepages. Other springs issue from the basin margins, but most seep into the ground or evaporate before reaching the lake. Shallow brine covers Clinton Lake during spring and early sum mer, but most of the surface is salt encrusted by late summer and autumn.Preliminary analyses of the basin waters and sediment mineralogy suggest that Clinton Lake may be fed by at least two distinct groundwater sources. The first type has a very high Na/Cl ratio (>15); the second type is less evolved, less saline, and has a lower Na/Cl ratio (<12). Both types of groundwaters have very high Mg/Ca ratios, resulting from contact with Mg-rich bedrock and early precipitation of calcite ce ments in soils.Aragonite and Mg-calcite are precipitated at the spring orifices, further deplet ing the waters in calcium. Some spring waters flow into Clinton Pond, where ara gonite and hydromagnesite precipitate. Pond waters, augmented by other springs, may seep below hummocky carbonate mudflats toward Clinton Lake. At Clinton Lake, these waters mix with other shallow, dilute seepage and possibly, artesian groundwaters discharging through the lake floor.Cores and surflcial muds from the saline mudflat contain hydromagnesite, ara gonite, dolomite, and magnesite, and gypsum. Most calcium and much of the car bonate are precipitated in the outer mudflat, leaving a M g-N a-S04 brine. Clinton Lake is a "spotted lake," consisting of more than 100 brine pools separated by rims of Mg-carbonate and gypsum muds. In summer, clear epsomite crystallizes in the pools as rafts and bottom-nucleated crystals. Mirabilite forms from residual brine in the autumn. Permanent epsomite deposits, showing evidence for repeated dissolu tion and recrystallization, underlie the pools.Clinton Lake is the successor to an earlier Mg-carbonate marl lake. Historical records suggest that evaporite precipitation could be very recent.

Cyclic development of large, complex, calcite dendrite crystals in the Clinton travertine, Interior British Columbia, Canada

“…Calcite is the only carbonate mineral found in the travertine, which commonly is N 98% pure CaCO 3 (Kerr, 1980). Although aragonite was precipitated at other springs in the area that have high Mg/Ca ratios (Renaut, 1994;Renaut and Jones, 2000), none has not been found in the Clinton travertine.…”

Multi-proxy Holocene palaeoclimatic record from a saline lake in the Canadian Subarctic

“…For example, development of the Mg-Na-SO 4 brines and deposits of epsomite recorded here are known to occur in other hydrologically closed basins where evaporation exceeds inflow (e.g., Hawkins, 1985;Renaut, 1994). Dominant diatom species during this interval included Cyclotella cf.…”

Hydromagnesite replacement of biomineralized aragonite in a new location of Holocene stromatolites, Lake Walyungup, Western Australia

“…A common feature of Holocene hydromagnesite and magnesite occurrences is that the source of Mg 2+ is interpreted to be from Mg-rich ultrama®c and basaltic rocks. Recent examples of hydromagnesite precipitation from the Coorong region and maar lakes of South Australia and Victoria (Von der Borch, 1965;Last, 1992), saline lakes in the Cariboo Plateau of Canada (Renaut, 1994) and Salda Go È lu È in Turkey (Braithwaite & Zedef, 1994 all call on ultrama®c bedrock sources to supply excess Mg 2+ to groundwater entering hydromagnesite precipitating lakes.…”