Discriminating cool‐water from warm‐water carbonates and their diagenetic environments using element geochemistry: The Oligocene Tikorangi Formation (Taranaki Basin) and the dolomite effect

Abstract

Fields portrayed within bivariate element plots have been used to distinguish between carbonates formed in warm-(tropical) water and cool-(temperate) water depositional settings. Here, element concentrations (Ca, Mg, Sr, Na, Fe, and Mn) have been determined for the carbonate fraction of bulk samples from the late Oligocene Tikorangi Formation, a subsurface, mixed dolomite-calcite, cool-water limestone sequence in Taranaki Basin, New Zealand. While the occurrence of dolomite is rare in New Zealand Cenozoic carbonates, and in cool-water carbonates more generally, the dolomite in the Tikorangi carbonates is shown to have a dramatic effect on the "traditional" positioning of coolwater limestone fields within bivariate element plots. Rare undolomitised, wholly calcitic carbonate samples in the Tikorangi Formation have the following average composition: Mg 2800 ppm; Ca 319 100 ppm; Na 800 ppm; Fe 6300 ppm; Sr 2400 ppm; and Mn 300 ppm. Tikorangi Formation dolomite-rich samples (>15% dolomite) have average values of: Mg 53400 ppm; Ca 290400 ppm; Na 4700 ppm; Fe 28 100 ppm; Sr 5400 ppm; and Mn 500 ppm. Elementelement plots for dolomite-bearing samples show elevated Mg, Na, and Sr values compared with most other low-Mg calcite New Zealand Cenozoic limestones. The increased trace element contents are directly attributable to the trace element-enriched nature of the burial-derived dolomites, termed here the "dolomite effect". Fe levels in the Tikorangi Formation carbonates far exceed both modern and ancient cool-water and warm-water analogues, while Sr values are also higher than those in modern Tasmanian cool-water carbonates, and approach modern Bahaman warm-water carbonate values. Trace element data used in conjunction with more traditional petrographic data have aided in the diagenetic interpretation of the carbonate-dominated Tikorangi sequence. The geochemical results have been particularly useful for providing more definitive evidence for deep burial dolomitisation of the deposits under the influence of marine-modified pore fluids.

Geochemistry of Marine Carbonates from Hole 1394, off the Coast of Montserrat, IODP Expedition-340; Implications on Provenance, Paleoenvironment and Lesser Antilles Arc Migration

“…9) for the studied samples plot along with the Cenozoic New Zealand carbonates (but on the higher side of the Mn, Mg and Na) indicating their genesis in a temperate cooler waters but in actual condition the MVI (Lesser Antilles) is located in the zone of tropics which is a known latitudinal tectonic setting. Here we report a deviation from the general observation of Winefield et al(1996); Rao (1991), Hood et al(2004 and Azizi et al (2014) on the temperate limestones, although the geochemical parameters and ratios as mentioned above satisfy the discrimination. The authors also suggested that the regional generalisations can be made limited to the skeletal differences, diagenetic process involved etc., Based on the above and analysed data sets of the studied samples, the net effect of volcanogenesis, carbonate dilution and dissolution play an important role in discriminating the carbonates of tropical origins.…”

Guadalupian cool versus warm water deposits in central Iran: a record of the Capitanian Kamura event

“…Sr concentration and mineralogy composition of carbonates have a direct relationship, as Sr values increase with aragonite increase and decrease with calcite increase (Rao & Adabi, 1992; Rao & Amini, 1995; Rao, 1996; Adabi, 2004). Sr values range from 8000 to 10 000 ppm in recent tropical bulk carbonate samples (Milliman, 1974), while in recent temperate bulk carbonates it reduces and ranges from 1500 to 4500 ppm (Rao, 1991; Rao & Adabi, 1992; Hood, Nelson & Kamp, 2004). The values of Sr in low-Mg calcite, high-Mg calcite and aragonite are 1000 ppm, 3000 ppm and up to 10 000 ppm, respectively (Kinsman, 1969; Carpenter & Lohmann, 1992; Rao, 1996; Rao et al 1998).…”

Evidence of warm climate during late Sakmarian–early Artinskian in Posht‐e Badam Block, Central Iran and its paleogeographic implication

“…, ). Sr concentration also has a direct relation with increasing water temperature (Hood, Nelson, & Kamp, ; Morse & Mackenzie, ; Winefield, Nelson, & Hodder, ). Although aragonite recrystallization results in Sr loss (Brand & Veizer, ), but limestones with aragonite origin have naturally higher concentration than those with calcite origin (Veizer & Demovic, ).…”

“…The Sr content in recent tropical bulk carbonates ranges from 8,000 to 10,000 ppm (Milliman, 1974;Rao, Amini, & Ferguson, 1998), while in recent temperate carbonate it ranges from 1,600 to 5,000 ppm (Rao & Amini, 1995;Rao & Jayawardane, 1994;Rao et al, 1998). Sr concentration also has a direct relation with increasing water temperature (Hood, Nelson, & Kamp, 2004;Morse & Mackenzie, 1990;Winefield, Nelson, & Hodder, 1996). Although aragonite recrystallization results in Sr loss (Brand & Veizer, 1980), but limestones with aragonite origin have naturally higher concentration than those with calcite origin (Veizer & Demovic, 1974).…”