Waters, Pleistocene

Chloride is usually a major constituent in groundwater and is widely considered a conservative tracer. In the N aquifer, Cl- concentrations are considerably higher in Holocene water than in late Pleistocene water (Figure 9.3). The groundwater ages indicated on the horizontal axis are results from inverse mass balance modeling and age corrections (Zhu, 2000). These age data are also supported by the SD and S lsO data of the same samples. It is generally known that Pleistocene water has depleted H and O stable isotope values with respect to recent water because of a cooler and more humid climate in the late Pleistocene (Merlivat and Jouzel, 1979). 

There are also indications that climate-related shifts in wood 5 C of 1 to 3%o have occurred in time such shifts have been observed at the Pleistocene-Holocene boundary (Becker et al. 1991 Van de Water et al. 1994), and at later (Epstein and Krishnamurthy 1990) and earlier times (Aucour et al. 1993 Leavitt and Danzer 1992). Other temporal variations in plants can be seasonal (Leavitt and Long 1991 Loader et al. 1995). 

These different sites of hydrothermal and ore-forming activity may have resulted from the mode of subduction of the Pacific Plate. Mariana-type subduction (characterized by a steep angle of subduction and back-arc basin formation Uyeda and Kanamori, 1979) during middle Miocene caused WNW-ESE extension, submarine hydrothermal activity, thick accumulation of bimodal (basaltic and dacitic) volcanic activity (Green tuff) and Kuroko-type formation (Shikazono and Shimizu, 1993). Plio-Pleistocene Chilean-type subduction (shallow-dipping subduction zone, E-W compression Uyeda and Kanamori, 1979) and oblique subduction of the Pacific Plate beneath the North American Plate led to uplift and expansion of land area, subaerial hydrothermal activity accompanied by meteoric water circulation, subaerial andesitic volcanic activity and formation of vein-type deposits. 

Shackleton NJ, Imbrie J, Hall MA (1983) Oxygen and carbon isotope record of East Pacific core V19-30 implications for the formation of deep water in the late Pleistocene Nodh Atlantic. Earth Planet Sci... 

Harmon RS, Mitterer RM, Kriausakul N, Land LS, Schwarcz HP, Garrett P, Larson GJ, Vacher HL, Rowe M (1983) U-Series and amino-acid racemization geochronology of Bermuda Implications for eustatic sea-level fluctrration over the past 250,000 years. Palaeogeog Palaeoclim Palaeoecol 44 41-70 Harmon RS, Schwarcz HP (1981) Changes of H and 0 errrichment of meteoric water and Pleistocene glaciation. Natrrre 290 125-128... 

The Miocene stratigraphy in the Baguio District has been intruded by a series of Pliocene rocks. The homblende-phyric Mafic Dike Complex intruded the central part of the Baguio District at 4.5 - 4 Ma (Waters et al. submitted). The complex is characterized by dense clusters of coarsely hornblende phenocrystic dikes with evidence for multiple injections. Several Pliocene to Pleistocene dioritic intrusive complexes are associated with porphyry copper-gold mineralization in the Baguio district. The Black Mountain Intrusive Complex includes the Black Mountain quartz diorite and the Mexico Diorite, as well as andesite dykes that have yielded ages of between 3.14 and 2.78 Ma (Waters et al. submitted Sweet etal. 2008). Other Pliocene intrusive rocks... 

Pleistocene Epoch, courtesy The American Museum of Natural History. c Fossilized specimen, courtesy The American Museum of Natural History. d Collagenous material extracted with boiling water for 2 hrs. 

It is important to realise that clay can be exposed to many processes after it has been depos-ited. The periods are the Miocene Epoch (26 - 7 million years old), the Pliocene Epoch (7-2 millions years old), the Pleistocene Epoch (2 million to 15,000 years old) and the Holocene Epoch (up to approximately 15,000 years old). In The Netherlands no primary clay deposits are found, i.e. all clay is secondary, i.e. formed elsewhere and transported by wind, ice or water. 

Szramek, K Walter, L.M. and McCall, P. (2004) Arsenic mobility in groundwater/surface water systems in carbonate-rich Pleistocene glacial drift aquifers (Michigan). Applied Geochemistry, 19(7), 1137-55. 

Perhaps 150000 tube wells, most of which are private, exist in the Red River delta (Smedley and Kinniburgh, 2002). Groundwater is withdrawn both from shallow, hand-pumped tube wells at depths of <45 m and from public-supply wells, which tap the Pleistocene aquifer beneath the city of Hanoi at depths of 30-70 m (Smedley, 2005). In recent years, the rate of groundwater abstraction in and around Hanoi has increased dramatically with an annual water table decline of about 1 m (Tong, 2002) and a seasonal decline of about 30 m (Trafford el al., 1996). 

Neo-autochthonous Miocene to Pleistocene sediments (evaporites, lignite, fresh water limestones, conglomerates, clays, sands, etc.) infilling tectonic depressions formed during post-orogenic extension. 

Figure 7.29. A scatter plot of 813C and 8180 values of Holocene and Pleistocene carbonate sediments. Open circle, unlithified bulk Holocene sediments + s, lithified bulk Holocene sediment closed circles, Pleistocene limestones altered by meteoric water. For Pleistocene limestones altered in the meteoric environment, temperate climate samples are represented by 8180 values more enriched than -5%o, whereas tropical climate samples have 8180 values more depleted than -5%o. The large depletion in 13C is because the sediment samples are primarily from vadose environments. (After Land, 1986.)...

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