Sea Water: Dolomitization Essay

In site one there was a high proportion of very unspherical rocks. According to this the hypothesis is right, in site two there is a lot more smother rocks medium sized and in site 3 there are very small pebbles which are very smooth and spherical. The pebbles get smoother and rounder while it goes downstream. Due to us only taking about 10 rocks our result may have been not right as there were some pebbles which were largely over sized. Most of the other load is dissolved by solution such as limestone and chalk

The youngest of these rocks are dated at about 220,000 years ago. Rhyodacties and quartz latites in the modern caldera area extruded from about 320,000 years ago to 260,000 years ago, and then silica-rich rhyolites at Glass Mountain northeast of the caldera erupted from about 210,000 years ago to 80,000 years ago. The scattered distribution of the initial mafic eruptions indicates that they were erupted from the mantle, while the slightly younger domes and flows were from a deep-crustal source. The youngest rhyolite eruptions erupted at the northeast rim of the caldera at Glass Mountain and were the first activity of the silicic Long Valley magma chamber (Bailey, et. al., 1989).

Starved Rock State covers about 200 miles and some 470 million years, from Ordovician sandstones to Pleistocene glacial till. The Ordovician St. Peter Formation sandstone was deposited across the midcontinent during the second major marine transgression of the Paleozoic Era. The first transgression deposited Upper Cambrian to Lower Ordovician clastics and carbonates. The clastic to carbonate rock transition is consistent with gradual sea level rise over the North American craton. Sea level dropped late in the early Ordovician, exposing the carbonate strata to processes of cave development.

Next, we can see that the rock displays a subtle porphyritic texture with plagioclase comprising the phenocrysts. The overall texture of the surrounding groundmass is granoblastic equigranular. Under thin section we also see a weakly defined foliation evidenced in the preferential alignment of actinolite grains and to a lesser extent chlorite grains. Undulose extinction is also observed in quartz indicating the rock was subject to deformation. The normalized quartz, alkali-feldspar, and plagioclase (QAP) values of this rock indicate that it is classified as a grano-diorite according to the IUGS QAPF classification system which is consistent with the hand sample interpretation.

Sims et al. (1989) synthesized U-Pb zircon ages for the Pembine-Wausau terrane. Sims concluded that the volcanic rocks were generated from around 1889 to 1860 Ma as island arcs and closed back-arc basins above the south-dipping subduction zone (Niagara fault zone). Granitoid rocks in the terrane, emplaced from around 1870 to 1760 Ma, are mainly granodiorite and tonalite but include gabbro, diorite, and granite. These developed as island arcs above the Eau Pleine shear zone. The Niagara fault zone contains a relict ophiolite, suggesting that the rocks in the Pembine-Wausau terrane probably accumulated on

The country rock was identified in the field to be a Meta-Limestone, but a more in-depth chemical analysis done by others classifies it as a dolostone of the Strath Suardal formation from the Durness group. (Digimap, 2017) (Goodenough et al. 2011)

Rodinia started to rift around 750 to 600 million years ago and the Iapetus Ocean opening up as seen in Figure 1, the Swift Run Formation with Grenville, volcanic debris and ash material produced the Catoctin Formation that contains flood basalts supporting Shenandoah. With modern day East Africa rift and Red Sea curst stretched, this allowed flood basalts and rhyolite seep through the ocean floor and eventually made its way to the surface.

On June 19th, my classmates and I had field trip for Oceanography Lab (OCN 101) class with Professor Ocean Matt Horrigan. We went to Corte Madera Salt Marsh, which is located 12 miles North of San Francisco, to examine how rising and falling of tide effect on

The Waucoba Wash Quadrangle, California cross section begins with the deposition of the Cambrian layers such as the Campito Formation, Poleta Formation (upper and middle members and undivided), Harkless Formation, Saline Valley Formation (lower and upper members), Mule Spring Limestone, Monola Formation (lower and upper members), and the Bonanaza King dolomite (dominantly limestone and undivided). These Cambrian rocks are followed by rock layers from the Devonian period, thus meaning that an unconformity occurred between the layers. The Devonian dolomite rock layers include the Hidden Valley dolomite and the Lost Burro Formation (cherty dolomite). These are followed by the Mississippian

The Buffalo River area is a karst environment with attendant sinkhole and cave formation. Limestone, composed primarily of CaCO3 and dolomite composed primarily of CaMg(CO3)2, are the two soluble rock types in the area that host the karst features. Water in contact with air picks up carbon dioxide some of which transforms to carbonic acid, and this acid then dissolves the carbonate minerals, carrying the ions out in solution (e.g. Trudgill 1985). Limestone and dolomite layers vary in impurities and grain size so that different layers are more or less prone to dissolution, with dolomite generally being less soluble than limestone. To erode these rock formations with very low intergrain porosity and permeability, there has to be exposed surface area and so faults and joints within the rock greatly increase the rate in which the rock will dissolve, and partly control the location of

Bradbury’s (1967) dissertation research was the first comprehensive study of Zuni Salt Lake maar. Based on a radiocarbon age of 22.9 ± 1.4 ka 14C yr BP (Haynes et al., 1967) on aquatic, calcareous algae from Zuni Salt Lake lacustrine deposits 15 m above the present lake level, he concluded that the Zuni Salt Lake maar formed during the late Pleistocene. This single date provided a maximum age for the Zuni Salt Lake maar but has long been viewed as suspect because of probable hardwater carbon-reservoir effects. Subsequent argon dating of Zuni Salt Lake volcanic rocks resulted in low-resolution plateau ages of 114 ± 38 ka and 86 ± 31 ka (McIntosh and Cather, 1994).

This Lower Keg River member was initiated by a rapid increase in sea level elevation flooding the salt plains of the Contact Rapids. Campbell (1987) described the Lower member of a dark micritic limestone, in a somewhat “euxinic” environment, containing bitumen and fauna such as brachiopods, crinoids, corals, stromatoporoids and gastropods. The unit can be locally dolomitized with a maximum thickness of approximately 50m. The Upper Keg River member was deposited during the restriction of marine waters by the Presqu’ile Barrier reef into the Elk Point Basin (Campbell, 1987). The interior of the basin contains Upper Keg River pinnacle reefs, banks and platforms. Campbell (1987) noted the spatial differences in the type of carbonate deposition within sub-basins; areas from the Peace River Arch to southern Alberta show a fringing carbonate platform, while the Rainbow, Zama and Shekelie basins contained the majority of the

These Paleozoic rocks are steeply plunging sandstones and siltstones, with a little event of limestone at Lilydale - the Early Devonian Lilydale Limestone. The Silurian rocks were stored in profound water, while the Devonian rocks, which are exceptionally fossiliferous, appear to have been stored in shallower water. These Silurian and Devonian rocks were folded into a progression of anticlines

The Crato Formation lithologies were most likely deposited when there was a marine transgression; which is what the Cretaceous period is renowned for (Hu et al. 2012). The build-up of laminated limestones and different lithologies in the stratigraphic column could suggest that it was a lagoon depositional environment (Martill and Frey, 1998).

Glaciation that are widespread can be identified based on the subglacial tillite, which is a thick layer of sediments that settle down beneath glaciers or ice caps. On top of this subglacial tillite layer is deposited marine carbonate, also known as cap carbonate. Based on their paleolatitude designated by glacial sediments’ paleomagnetism, it can be determined that these deposits are from equator region. The interaction between two types of sediments, marine (like carbonate) and subgacially deposited sediments, indicate that the glaciers had approached marine coastlines.