Tridacna Research Paper

He noticed that the rocks at the top of the section had a very high percentage of fossils of living mollusc species. Those at the bottom of the section had very few living forms. He deduced that this difference was because of the extinction of older forms and the evolution of living forms during the time that the rocks were being deposited. He divided the Tertiary rocks into three sub-ages: the Pliocene, the Miocene, and the Eocene. 90% of the fossil molluscs in Pliocene rocks were living today. In the Miocene rocks, only 18% of the molluscs were of living species, and in Eocene rocks, only 9.5%.” (Polly et al.,

The author and his colleagues specifically chose to focus on 375 million year old rocks in their search for fossils because this was the time frame that provided fish that would be useful to study from. The 385 million year old rocks provided fish that look too similar to the ones we have now and the 365 million year old rocks have fossils that don’t resemble fish. The 375 million year old rocks, however, provide fossils that show the transition between fish and land living animals.

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For an existing habitat, an increase in salt levels will begin to show an effect on the abundance and diversity in species of zooplankton. This will exhibit a detrimental effect on the daphnia from the limited osmoregulatory capabilities of the organisms. This in turn can pose a risk to the level feeding rates and survival (Heine-Fuster, Vega-Retter, Sabat & Ramos-Jiliberto,

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).

Along the coasts of rocky beaches, an intricate ecological community inhabits the ‘rocky intertidal’ areas. The variety of rocks is home to an array of slimy, squishy, and colorful organisms. This intertidal community is comprised of nine species: three different algae, three stationary filter-feeders, and three mobile consumers. The three algae, Nori Seaweed, Black Pine, and Coral Weed, are the community’s producers and inhabit the bottom of the food chain. The next three species are stationary consumers. They are Mussel, Goose Neck Barnacle, and Acorn Barnacle. Because of their consumer status, they are more competitively dominant than algae. The last three components are the mobile consumers: Whelk, Chiton, and Starfish. They

At Disaster Beach, a refuse pile was discovered containing shellfish remains. The pile most likely came to be because of Cardium Sp., which was located two-hundred yards inland from the high tide line. The inland did not have a complete rainforest to support the semi-sedentary system, but there were eucalyptus plants that helped. The high points were the only logical place with grain processing and potential religious activity like having a Shaman look over the sites. However, the high points did not have any detectable stratigraphy when they were studied. Carbon dating of three shell samples, in three separate units was taken, and then returned. The shell fragments found on Disaster Beach were dated at the

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

The author and his colleagues chose to focus on 375 million year old rocks in their search for fossils because amphibians that look dissimilar to fish were discovered in 365 million year old rocks, while fish without amphibian characteristics were discovered in 385 million year old rocks. Thus, it is possible that the evolutionary intermediary, or the “missing link” between fish and amphibians, would be discovered in 375 million year old rocks, between the two time periods. The rocks examined were sedimentary in composition, as the gradual and relatively gentle formation of sedimentary rock under conditions of mild pressure and low heat are conducive to the fossilization of animal remains. Sedimentary rock is also often formed in rivers and seas, where animals are likely to live. This site provides a resource that describes means by which fossils are formed and how the fossil record may be interpreted, and shows some examples of fossils demonstrating evolution through geological periods: http://www.fossilmuseum.net/fossilrecord.htm. In 2004, Shubin and his colleagues were looking for fossils on Ellesmere Island, in northern Canada. This location was chosen because of its lack of human development, as well as of obstructing natural formations and life forms such as trees, which

I used to eat Trix cereal as a kid. But what really was good to me was the lucky charms. I remember one day trying to convince my mother that at the end of the rainbow was lucky charms for me and a pot of gold for her. Although that did not work. I never made it to the end. I am still tempted sometimes to go see what is at the end of the rainbow.

et al. (2000) estimated that the Holocene sedimentation in Patos Lagoon started ~8,000 yr BP, with an average deposition rate of 0.75 mm/yr. This is in agreement with marine sequences recorded in cores Bo, Mo and Pa. Core Bo has a thick marine package (21 m) deposited in the Patos Lagoon interior before 8,150-7,870 and after 7,640-7,430 cal years BP. Core Pa has a 2.5-m thick marine deposit followed by a 2 m marine-dominated deposit with rare freshwater influences. Similarly, the lower part of core Mo has a thin (0.5 m) marine-dominated deposition followed by a 4.8-m thick marine-dominated deposit with uncommon and rare freshwater taxa (at interval between 15-10.5 m), deposited before 8,160-7,920 until 7,980-7,750 cal years BP. Only after that, marine-dominated deposition is reestablished from 10.5-7 m at around 7,960-7,680 cal years BP. Also, the high marine influence is observed in distinct environments of coastal plain. A 7.5-m thick marine transgressive package is deposited before and after 8,420-7,930 cal years BP., in the extension of the Barra Falsa channel (core B2). Similarly, the sediments of Peixe Lagoon (core T09) are composed by a homogeneous marine package deposited from 7,420-7,020 to 5,370-5,340 cal years BP (see Santos,

Increased terrestrial influx could have served as nutrients for algae and plankton and stimulated high bioproductivity at surface water. The oxygen in surface water would have been over-consumed by respiration and decaying of marine organisms, which was thought to trigger marine anoxia (Algeo et al., 1995). In this process, lighter isotope of carbon was preferentially taken up by aquatic organisms and therefore removed from the system, producing heavy carbon anomalies (Wang et al., 1996). Consequently, positive excursions in δ13C values were observed across the F-F boundary (Figure 2). In addition, higher bioproductivity would bring about elevated burial rate of organic carbon (Wang et al., 1996; Chen et al., 2002)

As short-term mineral-fluid exchange could be a viable process responsible for significant alteration of proxy archives in marine settings quantifying the rate exchange and evaluating its extent on the geochemical proxies is critical. One of the prerequisites for foraminifera-based proxy reconstruction is calibrating the sensitivity of the proxy against the physical, chemical, and biological factors using modern foraminiferal tests. Such calibrations are performed either using cultured foraminifera in controlled laboratory conditions or using modern foraminifera collected from sediment traps within the seawater column and from the core-top sediments at sediment-water interface. In marine settings three main regions where modern foraminiferal tests can be exposed to short-term mineral-fluid exchange are: 1) surface ocean, 2) deep ocean, and 3) seafloor/sediment-water interface.

Geochemical proxy-based reconstruction widely utilizes the trace elemental and isotopic compositions of marine biogenic carbonates to interpret the past climatic and oceanographic conditions. However, such proxy-based reconstructions are often challenged by marine diagenesis as carbonates are highly susceptible to diagenesis, especially partial dissolution and secondary calcite recrystallization. Thus quantifying diagenetic effect is a prerequisite for development of any carbonate-based geochemical proxy. Among the metal isotopes, Mg isotopic composition (δ26Mg) of foraminiferal carbonates is a promising proxy to reconstruct the secular seawater δ26Mg variability, which is useful in understanding long-term changes in Mg geochemical cycle. However, as the trace metals like Mg in marine carbonates show greater susceptibility to diagenetic alterations due to its low abundance as compared to that in the co-existing pore fluids, development δ26Mg of marine carbonates as a geochemical proxy critically requires a thorough understanding of the fractionation behaviors of Mg isotopes during diagenesis. Therefore, the primary goal of this dissertation is to quantify the effect of diagenesis on metal isotopes, in particularly, δ26Mg of marine carbonates from various depositional settings to evaluate the effect of advection, diffusion and lithological variation within the sedimentary column on the extent of calcite diagenesis. For this purpose, trace elemental (e.g., Mg/Ca and Sr/Ca) 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.