RESEARCH INTERESTS AND HIGHLIGHTS:
My research primarily involves elucidating the effect of diagenetic recrystallization on metal isotopes (Mg, Ca, and Sr) in marine carbonates and evaluating their reliability as geochemical proxies to reconstruct the paleoclimatic conditions and chemical evolution of seawater through geologic period. Geochemical cycling of Mg on the earth’s surface involves transfer of Mg from continental rocks to the ocean followed by reincorporation of Mg into the lithosphere via hydrothermal exchange at the mid-oceanic ridges and through precipitation of carbonate minerals. Since the exogenic cycle of Mg is directly linked to the global carbon cycle it is invaluable for reconstructing the climatic variability (e.g. pCO2 and temperature). The Mg isotopic composition (δ26Mg) of seawater is useful to decouple long-term variability of Mg concentration and δ26Mg of the input and output fluxes to the ocean. The δ26Mg of marine carbonates is a promising proxy for seawater δ26Mg. However, diagenetic recrystallization of calcite, which is known to impact the trace elemental and isotopic composition of carbonates significantly, can complicate the carbonate-based geochemical proxy interpretation. Therefore, it is critical to quantify the diagenetic effect on the concentrations and isotopic composition of trace elements (e.g. Mg, Ca, Sr) in carbonates to facilitate accurate proxy reconstruction.
My doctoral research is focused on quantifying the effect of
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It was assumed that these carbon values were unaffected by the diagenesis since aqueous fluids typically have an insignificant amount of carbon in comparison to carbonate rocks. In addition, stratigraphic mapping showed that there was no tectonic activity in this area that would have affected diagenesis either. Results indicated that the proportion of organic carbon to total carbon burial changed from roughly 0.5 before the glacial deposits to virtually 0 immediately after. [Hoffman et al., 1998]. These numbers indicate that life struggled during this interval and the snowball Earth theory might explain why. Oceanic photosynthetic bacteria and eukaryotes would have been severely reduced because global ice cover would have blocked the sun making photosynthesis very difficult. (maybe also use top of 1344 to talk about theory on how snowball earth ended; Should I maybe use separate part of paper for theory and evidence. They tie together pretty
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).
The base of IIIb1 appears slightly oxidized and yielded an age of 2277± 36 14C yr BP. Above this is a ~60-cm-thick, organic-rich “black mat” (IIIb2) consisting of multiple thin beds containing varying amounts of plant matter including both decomposed humic material and uncharred plant macrofossils that constitute a significant proportion of the sediment volume in the most organic-rich deposits. The IIIb2 black mat was formed between 1934 ± 29 14C yr BP and 1759 ± 25 14C yr BP, with the most organic-rich portion predating 1833 ± 36 14C yr BP. Organic carbon content of the black mat varies, but the highest values are ~2%. Plant remains in IIIb2, consisting mostly of bulrush achenes and pollen, indicate emergent aquatic floodplain vegetation, and the unidentifiable stem fragments ubiquitous throughout the layer are likely also bulrush (Figure 8). Faunal remains within IIIb2 at 11-37 include snail and ostracode species indicative of marshy conditions (Table 4). From the base of IIIb1 to the sharp upper boundary of the IIIb2 black mat, a trend of decreasing calcium carbonate, increasing gypsum, and increasing organic carbon is evident. Gypsum content ranged from 3.7–16.6% and occurred as tiny clumps of intergrown lathe crystals, whereas carbonate content ranged from ~4–13% and occurred as small soft
Correspondence concerning this article should be addressed to Lauren Howell, Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4
The Peninsular terrane is a Triassic to Jurassic island-arc complex that was accreted to the North American craton by the Early Cretaceous (Detterman and Reed, 1980; Jones et al., 1987; Ridgway et al., 2002; Trop et al., 2002, 2005; Clift et al., 2005). The terrane includes mafic to andesitic flows and volcaniclastic rocks, limestone, and mudstone. These rocks structurally overlie and are intruded by Jurassic plutonic rocks of the Talkeetna arc (Reed and Lanphere, 1973; Reed et al., 1983; Rioux et al., 2010). The plutonic rocks include gabbroic to granitic compositions, but are dominated by quartz diorite and tonalite rocks (Detterman and Reed, 1980; Reed et al., 1983).
Late Devonian paleoclimate proxy records indicate substantial sea level variations, however a thorough understanding of the Late Devonian climate and the causes of these fluctuations remain uncertain. Numerous theories, including glaciation, bolide impacts, global anoxia, and the spreading of land plants are attributed to these events. This paper attempts to test the plausibility of the glaciation hypothesis by applying Late Devonian boundary conditions to a general circulation model (GCM). A Late Devonian paleo-reconstruction is combined with soil and vegetation, pCO2, and obliquity parameters. Temperature and precipitation patterns indicate that it is possible for mountain glaciers to form in regions of Gondwana that have both high latitude and altitude. However, because there is a low temperature gradient between the equator and poles, the climate is comparable to post-industrial greenhouse climates. Therefore, these GCM simulations provide a greater understanding of Late Devonian climate conditions and add validity to Late Devonian glaciation.
A: This isotope would not be very useful for dating bones that are over a million years old. This is because carbon is in the living plants and animals since they consume nutrients with it and the air they breathe contains it. When
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.
Using the taphonomic number described above and displayed in Table 2; I examined the relationship between diagenesis of the recently dead to the variation seen in both of the stable isotope records acquired here (Figure 3). The average value of each taphonomic number is not as important as the fact that one standard deviation (represented by error bars) increases from about 0.2 ‰ to 0.8‰ in δ13C values, and 0.3‰ to 0.9‰ in δ18O values as the taphonomic number increases. If this relationship is universal, it represents a significant impact on the records acquired by damaged, fossil or recent shells. As stated in the introduction some studies have examined the impact of
Welcome to one of the planets most obscure but important features, known rather prosaically as the mid ocean ridges. In 1973 a group of oceanographers discovered this ridge of mountains on the ocean’s floor. Since then, they have been more closely exploring the ridges and studying how they move and exactly what they are. They have come to discover, that the “ridges feature long rift valleys and, down their middles, giant fields of gushing, hot springs that shed tons of minerals into icy sea water at the bottom of the sea,” which over time has come to create these huge mid-ocean ridges where many animals like to live, cause its some warm.” A main question is to what extent the volcanism changes over time. The old idea was that the eruptions
Since the industrial revolution, anthropogenic inputs of carbon dioxide to the atmosphere have increased dramatically. Concentrations in the atmosphere have risen 40% from 1750 to 2011, reaching record highs of 390.5 ppm (Stocker, et al., 2013). Due to this, the amount of dissolved CO2 in the oceans has also increased causing acidification of the oceans which can have several effects, mainly on calcifying organisms. Climate change has also influenced the stratification of the oceans due to density changing affecting nutrient distribution. So far, although a number of methods have been explored, there have been no solutions that don’t have their own issues.
Another aspect of the Archean Eon that is important was the formation of Earth’s atmosphere and oceans (Lutgens and Tarbuck). Earth’s oceans formed from volcanic discharges of water vapor (Lutgens and Tarbuck). Due to the cooling of the Earth, the water vapor condensed at the surface and then formed into liquid water (Lutgens and Tarbuck). The salts that are found in the seawater today are from eroded sediments and
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 earth’s past is full of dramatic climate changes. Many glacial advances and retreats have occurred during the last billion years of Earth history. Large, important glaciations occurred during the late Proterozoic (between about800 and 600 million years ago), during the Pennsylvanian and Permian (between about 350
SB-3 lies in grainstones in Blowfire-1 and is dated approximately 33 Ma. After this boundary sedimentation starts with photozoans, but with the increasing sea levels, algae and benthic foraminifera become abundant that shows a transition in the carbonate factory, where MFS-3 is also observed. The deposits overlaying SB-3 start with photozoans that are micrite dominated and continues with a transition to heterozoans. In upper sections, sedimentation continues with algae and benthic foraminifera dominated carbonates. Also, common dolomitization in this section marks an unconformity as the characteristics of this dolomitization represents a subaerial exposure after deposition of this stack of carbonates.