Geochemical Proxy Based Reconstruction : The Trace Elemental And Isotopic Compositions Of Marine Biogenic

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).

Limestone containing ammonites Likely from the cretaceous, formed with the transgression and regression of ocean waters, possibly 70-100 million years ago at which time the sea transgressed and regressed a number of times. The presence of the ammonites suggests that the formation was from the upper Cretaceous period. Limestone is a sedimentary rock, composed largely of calcite and aragonite, which are both different forms of calcium carbonate. It makes up about 10% of the total of sedimentary rocks. It is composed of grains of skeletal fragments of marine organisms, pressed together over time with variable amounts of silica.

The Purisima Formation is extensively allocated “in central California from coastal exposures at Point Reyes in Marin County to more extensive exposures in the Santa Cruz Mountains from the coast in San Mateo and Santa Cruz Counties inland to the San Andreas Fault.” These scattered visible rock formations are part of the Purisima Formation because they all share a few specific characteristics: They all have interbedded mudstone, siltstones, and very fine-grained sandstones, with abundant shell debris. The Purisima formation was created “about 3 to 7 million years ago during the late Miocene and the Pliocene through a 4 million year period of deposition: The deposited rocks record a shift from deeper offshore conditions (primarily siltstone

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.

Research included conducting a geologic survey of the Congo craton, facies of Ghaub formation fill valleys. Rock specimens were taken from the lower glacial intervals (Chugs Formation) to just beneath the unconformity at the base of Mulden group, Southern Damara margin of the craton and Kaoko craton, Kalahari craton, Amadeus basin. These rock specimens were microdrilled and the elements Sr, Mn, Fe, Ca, Mg were measured for abundance using inductively coupled plasma emission spectoscopy to assess diagenetic alteration. These sample were analyzed offline for DELTA 13 CARBON AND DELTA 18 OXYGEN after digestion for 3 hours in H2po4 at 50'C to insure complete reaction of dolomite: the evolved gas was measured on a finnigan mat, other research consisted of fisions secter mass spectrometer, graphite -furnace atomic absorption spectoscopy, leached in NH4CH3COO, digestion in weak acetic acid. (Hoffman, et. al. 1998)

Plate tectonic convergence at a rate of about 4 mm/year between the Eurasian and African. Plates dominates the straits of Gibraltar (Argus et al., 1989). The stratigraphic evolution of the sediment drifts is therefore greatly influenced by both regional tectonics and ocean circulation (Medialdea et al., 2009; Lopes et al., 2006; Terrinha et al., 2009; Zitellini et al., 2009). Coring results from Expedition 339 showed that initial contourite formation started at about 4.5 to 4.2 Ma ago with more prominent formation of the contourite drifts taking place in the Quaternary (Expedition 339 Scientists, 2012).

It was also found that the amplitude of δ18O was greater in specimens gathered from shallow water because of greater environmental variability (1989). Specimen found deeper had higher δ18O and δ13C when compared to the shallow specimen due to lower temperatures and the lesser influence of 13C depleted carbon from oxidation of organic matter in sediments and meteoric water (Romananek et al.,

Perhaps the canonical distinction is the isotopic composition of the extruded igneous rocks. In mid ocean ridge basalts (MORBs) and subductive volcanoes, the ratio of 87-strontium, a decay product of 87-rubidium, to 86-strontium is approximately .7025. However, in hotspots, this ratio is substantially greater, averaging .7038. These two ratios cannot be equated by natural variation – the difference is too large. Instead, the magma resulting in each feature likely emerges from a different geochemical reservoir, and thus possesses a distinct geochemical signature. Another confounding factor is the existence of linear intraplate oceanic ridges. In 1963, Dr. John Wilson established a linear relationship between the age of an island and its distance from an active volcanic source. A resultant implication, when corroborated with plate tectonics, is that the hotspot is fixed relative to the mantle. In theory, the motion of the plate over the hotspot causes the production and subsequent geologic death of hotspot-generated

The Earth has experienced 5 notable mass extinction events to date; these extinctions have impacted coral reef systems significantly. Every occurrence of mass extinction has left the Earth without living reefs for millions of years. These intervals of absence are often termed ‘reef gaps’ (geological intervals where there are no traces of what might have been existing reefs). The sources of these ‘events’ will be discussed further. The primary causes of mass extinctions are linked to the carbon cycle and make-up of the oceans. The acidification of our oceans is argued to be the most serious of all the predicted consequences of C02 increase, due to anthropogenic behaviors. This article will be inferring that acidification has the potential

Marine Sediments are the particles of organic or inorganic matter that accumulates in a loose, unconsolidated form. After the continuous raining of sediments, the deep floors have varied from centimeters of thickness per year. When we think of sediment, we think have erosion of minerals that were once on land, remains of living organisms, and chemical reactions that associate with the ocean (terrigenous,biogenic, hydrogenous, and cosmogenic ). This process has helped determine the age of the seafloor and what it may be in the future. Sediments are like the memory of the ocean, due to the recycled tectonic plates, only dates back to 180 million years ago. Although the ocean cannot reveal its early history, sufficient evidence has allowed

Stable isotopes such as carbon-13 and carbon-12 do not decay like carbon-14. During photosynthesis carbon-12 is more easily absorbed by plants due to it being lighter then carbon-13, as it’s heavier. Therefore when there is a particularly high photosynthesis rate more carbon-12 is absorbed by organisms and thereafter preserved in the sedimentary rock. The atmosphere and ocean have more carbon-13 than carbon-12 as it’s more readily absorbed at this time. Carbon-13 created carbonate skeletons in the ocean, phytoplankton have calcium carbonate

1. One of the paramount topics we have covered in this course is oceanography (no surprises there). Rather than thinking of oceanography as “just” the study of the ocean, I have always viewed oceanography as the study of marine biology, marine chemistry, marine geology and marine physics. Before diving into any sort of detail, one can see (from the above) that oceanography incorporates four fundamental sciences into one topic; therefore, when asked to list three ways in which marine geology and marine chemistry interrelate, the possibilities are endless. Because we are to list just three examples, I am going to focus my answer on the Earth’s composition/layers. The first way these two fields interrelate is though convection currents (mantle). Density and temperature are two topics central to chemistry. Because density and temperature, along with depth, play a critical role in plate movement (geology), the plate tectonic theory is one example. The second way is through radioactive decay. Specifically, we use radioactive dating (e.g., isotope dating and half-lives) to determine the exact age of a specific geological structures. The third way these two fields interrelate is in determining the composition of the Earth’s inner core. I saved this example for last because it shows how marine physics can also be interrelated in marine chemistry and marine geology. We [scientific community] have a sound understanding of the Earth’s composition because of mass, density and temperature

By testing sediment and recording whether it was deposited under conditions of normal polarity and then measuring successive layers, we can build a time chart. By matching different charts from different areas with similar fossils, a more global correlation can be made.

The creation of marine isotope stages we know today was a carminative effort between several scientists and research institutions across decades. It first started with Cesare Emiliani who transferred to the University of Miami’s Institute of Marine Science in 1957. Emiliani had been investigating the cause and nature of Quaternary glaciations by examining foraminifera fossils from the marine sedimentary record for the Pleistocene Age. Moving to the University of Miami offered new opportunities for Emiliani to work with ongoing drilling projects and trained individuals. Emiliani’s work was heavily influenced by Harold Urey’s 1947 work on

One of the conundrums of carbonate diagenesis is that seawater is supersaturated in dolomite, yet dolomite is rarely directly precipitated in the present day. Discuss the strengths and weaknesses of different mechanisms that have been postulated to explain dolomitization, and why it is important to understand from a hydrocarbon perspective.