A Brief Review Of Marine Isotope Stages

Studies of the age of molten rock in the ocean crust confirm the magnetic data. Molten rock contains radioactive isotopes used to calculate the time of the eruption. Rocks near the Mid- Atlantic Ridge, in addition to current like structures happened to be rather young, only some million years aged or a lesser amount (Trefil & Hazen, 2010). Rocks gathered one after another farthest from the range established them to be in turn older. Up to date evidence on charting the surfaces of oceans, maps of rock magnetism, and data on the age of rock indicate to countless expert that the span of the Atlantic Ocean for all intents and purposes is

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.

In order to find evidence of the transition from fish to land animals, the author and his colleagues chose to focus on 375 million year old rocks. In 2004, they studied sedimentary rock on Ellesmere Island in Canada’s Arctic as they thought that the rocks there would be exposed and untouched by humans, which would be ideal for fossil excavations. They studied sedimentary rocks (limestone, sandstone, siltstone and shales) because these

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).

Hildebrand, (2009, 2003) attempts to integrate both observed geologic features (hinterland high grade metamorphism, Laramide basement uplifts, Cordilleran batholiths, regional-scale Neogene extension) and the lack of observed features (large scale strike/slip faults), while matching paleomagnetic data (large amounts of northward motion in the oceanic realm exist with no evidence on land) (Fern Esperanza beetle-Moorcroft, MS Thesis, 2014).

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

5. Why did it take so long for free oxygen to accumulate in the atmosphere and in the oceans?

It caused a major change in the marine environment and fossil records. This geological event gave rise to ecological biodiversity. Animals that emerged were different and possessed distinct morphological

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,

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.

Palaeontologists divide fossil Lagerstätten into two types; Konservant-Lagerstätten (Nudds & Seldon, 2008), or conservation deposits, are horizons that show exceptional preservation of organisms, this may also include soft part preservation in some cases (Clarkson, 1998). This type of preservation usually occurs due to the inhibition of decay of the soft tissue (Briggs, 2014). For marine fossils, this can occur because of either rapid burial of the biota (Clarkson, 1998) or deposition in areas of low oxygen concentration (Briggs, 2014).

Ammonite taxa often occur in narrow time ranges, arguably making them the best index fossils to determine the ages of strata of certain time intervals (Callomon, 2003). The fossil remnants of ammonites act as the major basis for the identification of Jurassic and Cretaceous strata in the Sverdrup Basin, reinforced by the presence of bivalves, dinoflagellates, and foraminifera (Galloway et al., 2013). While macrofossils such as ammonites are used to define every stage of the Jurassic and Cretaceous periods in the Sverdrup Basin, detailed chronostratigraphy is limited by the rare occurrence of ammonite fauna (Callomon, 2003). This may be due to the colder climate conditions of the Arctic Boreal Sea relative to the subtropical conditions of the

Foraminifers are better known for their spectacular fossil record than for their variety or abundance in modern marine environments. They, however, constitute the most diverse group of shelled microorganisms in modern ocean The facts that benthic Foraminifera fossilize well, and may constitute the only tracers of ancient benthic environments, provide an additional reason to investigate the ecology of both epifaunal and infaunal components of the assemblage (Sen Gupta, 2007).

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

These techniques led to the discovery of the boundary between the two eras. A single thin layer of clay found within predominantly limestone rocks established this. By comparing the marine life found in, above, and below the clay, the marine life, like the dinosaurs, had been terribly affected by the extinction event. The percentage of life in the upper layers was dramatically lower than that in the lower. This was far more compelling than what was suggested by dinosaur’s fossils.