Lakes ephemeral

The Lake Eyre Basin in Australia contains the world s largest ephemeral lake. During the Quaternary the climate fluctuated between relatively arid and... 

Rundle Formation Oil Shale. The Rundle oil shale was deposited as a 300 meter thick sedimentary section in a freshwater, ephemeral lake/ depositional cycles in the Rundle are described by Coshell (4 3). A typical cycle began with periods of multiple transgressive-regressive... 

Pan/lacustrine silcretes (Figure 4.5B, C) most commonly develop within, or adjacent to, ephemeral lakes, pans or playas within endoreic basins (Goudie, 1973 Summerfield, 1982 Figure 4.10C). In the majority of modern evaporitic lacustrine environments, silica precipitation is driven by changes in pH and salt concentration (Thiry, 1999), both of which can... 

When lakes form in large topographic depressions, such as rift valleys or wide glacial U-shaped valleys, their biogeochemical sediments are differentially eroded, forming hills with flat tops (Figure 9.4A, D). Erosion of lake sediments can also lead to relief inversions. For example, ephemeral lakes... 

A playa lake, following Briere (2000), is an arid-zone feature, transitional between playa and (perennial) lake, neither dry more than 75% of the time, nor wet more than 75% of the time. When dry, the basin qualifies as a playa. Playa lakes may be broadly equivalent to ephemeral lakes and saline lakes, in some regional terminologies. 

Wright, D. T., 1999. The role of sulphate-reducing bacteria and cyanobacteria in dolomite formation in distal ephemeral lakes of the Coorong region. South Australia. Sed. Geol. 126 147-157. 

Layered chemical sediments may contain a variety of dissolution features produced by contact with undersaturated waters such as rounded or truncated crystal surfaces, rounded dissolution cavities, and vertically-oriented dissolution pipes (Fig. 3D and 3E). The frequency and nature of these syndepositional dissolution features may be used to distinguish perennial saline lake deposits from saline pan (ephemeral lake) sediments (Li et al., 1996 Schubel Lowenstein, 1997). In very shallow water (centimeters deep) to subaerially-exposed environments, layered halite crusts have little to no protection from incoming... 

Iron may be concentrated in acid mine waters and naturally occurring groundwaters. Natural flocculents of iron(III) oxide occur when iron-rich groundwaters enter the surface environment and are rapidly oxidised. These can form relatively pure ochreous deposits in ephemeral lakes and waterways or form as either a scum or muds in wetland environments. Evidence for the use of this material as a pigment is documented in Scott et al. (2002). 

Bone and tooth enamel from modem animals were collected in 1984 and 1993 from skeletons exposed on the surface in Sibiloi National Park, located on the east shore of Lake Turkana in northern Kenya. In addition to its interest as the site of numerous fossil hominid discoveries, the Turkana area provides an ideal controlled situation for the present study. The park is a circumscribed area surrounded by human pastoral groups and the nondomestic fauna remain to a great extent within its confines. Water sources are limited to the lake, ephemeral streams, a limited number of waterholes, and the plants eaten by the animals. The streams last on the order of days and in dry years do not flow at all. The non-domestic animals from which the bone and enamel were collected likely obtained most of their drinking water from the lake itself Domestic animals entered the park in 1984 during a severe drought. Their drinking water sources may have varied widely. 

Freshwater turtles home to their pond when experimentally displaced. Painted turtles, Chrysemyspicta, homed from 100 m, but not from 1.6 km (Emlen, 1969). They use chemical cues painted turtles discriminate chemical cues from their home ponds and other ponds. Males and females prefer water from their home pond to that from other ponds (Quinn and Graves, 1998). The Eastern long-necked turtle, Chelodina longicolUs, of southestern Australia uses solar cues during migration between a permanent lake and an ephemeral swamp, as... 

In addition, reductive dissolution of Fe or Mn (hydr)oxides at the sediment-water interface may be an important but ephemeral (seasonal) source of IAG in the anoxic hypolimnia of lakes. The nature and potential importance of each of these processes is described briefly as follows. 

Major saline systems at the borders of the Sahara include the large, ephemeral playas of Tunisia and Algeria, and the large, areally fluctuating, Lake Chad. Bryant et al. (1994) have described the principal control of the geochemistry of the Chott el Jerid in Tunisia by runoff from Cretaceous through Quaternary... 

In this chapter emphasis is given to bedded evaporites that have precipitated from lake- or groundwater in ephemeral lacustrine or playa systems. Bedded terrestrial evaporites may be classified according to ... 

Fluvial deposits (in isolation, and commonly as streams feeding the closed lake basins, Figure 10.3C) (f) alluvial fan-sandflat, (g) ephemeral stream floodplain and (h) perennial stream floodplain. 

Magnesite precipitates at depths of a few decimetres below the sediment-water interface, such as in the ephemeral salt pans of Recent playa lakes in north-east Spain, where precipitation is enhanced... 

The overall depositional environment of the Middle Lunde Member represents a distal alluvial plain or terminal basin (Nystuen et al 1989 Steel Ryseth, 1990 Nystuen Fait, 1995). Depressed areas were flooded by ephemeral sheet floods, leaving blankets of sand, silt and mud of high lateral extent. During certain periods these depressions could turn into shallow temporal lakes in which laminated, current-ripple laminated and wave-ripple laminated mud and silt aggraded. Drying up of these shallow lakes gave rise to frequent desiccation cracks, distorted lamination and mud flakes. The episodic flooding promoted the infiltration of suspended clay particles into the sand blankets. 

Closed systems, such as the wetlands that receive most of their water from precipitation (e.g., bogs, pocosins, and some seasonal or ephemeral wetlands), are oligotrophic and typically have low primary productivity. Increased inputs from surface and ground water can increase primary productivity in fens and marshes. (Table 5.5) Wetlands that receive pulses of nutrients, such as river floodplains, littoral zones in lakes, and tidal marshes, are typically very productive (Sharitz and Pennings, 2006). 

Nevertheless, the isotopic study of lacustrine carbonates for the purpose of paleoenvironmental reconstruction is far from a quick and simple routine for two reasons (1) bulk carbonates in lake sediments are composed of several components, each having a different source and thus containing different information and (2) a lake may be supported by variable amounts of groundwater and surface water, and range from ephemeral or permanent and small to large and thus tends to be a more complex system than the ocean, demanding a full accounting of the factors that affect its stable-isotope values and hydrochemistry (e.g., Gat, 1995 Hostetler, 1995 Winter, 1995). 

Subaerial Halite Crust Perennial Saline Lake Ephemeral Saline Lake... 

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