seqstrat_characterising
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seqstrat_characterising [20/03/2023 13:49] – mike_gss | seqstrat_characterising [11/05/2023 12:36] (current) – mike_gss | ||
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We need to establish characteristic " | We need to establish characteristic " | ||
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+ | Readers should be familiar with the biostratigraphical principles and applications to (a) Biostratigraphy and Correlation and (b) Paleoenvironments (see [[start|Table of Contents]] on home page). Sequence biostratigraphy brings these two aspects together in a fully integrated way. | ||
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(The LSF and SMW are often not developed) | (The LSF and SMW are often not developed) | ||
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+ | A sequence is formed during a cycle of a sea-level fall and subsequent rise (described on other pages). We can make an educated assumption as to how fossils - both those that dwell on or in the sea floor sediment and those that float or swim above it - might respond to these changes. These responses should be visible in the fossil record within a sequence. | ||
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+ | Often, a sea-level fall will expose the continental shelf and cause erosion and sediment re-deposition (the SB). Marine organisms that inhabited the continental shelf would die out. Erosion/ | ||
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+ | When sea-levels rise (during a transgression - TST) the exposed shelf is gradually submerged and bottom-living organisms can re-colonise the newly created environmental niches. Planktonic organisms can also be re-introduced as sea-levels rise. During this phase, sea-level rise is often rapid and water-depths get progressively deeper, resulting in a " | ||
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+ | When sea-levels reached their maximum landward extent (the MFS) planktonic organisms thrive and leave their fossil traces across the entire basin and are often the dominant microfossil types. | ||
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+ | During the high-stand phase (HST) sea-levels are high but do not change much. The continuing build-up of sediments raises the level of the sea-floor and water-depths shallow progressively resulting in another " | ||
It is important to note that, at a single location - such as the vertical penetration by a borehole of a subsurface sequence - not all sequence components will be encountered. For example, when encountering the distal part of a sequence it is unlikely that any HST sediments will be observed. | It is important to note that, at a single location - such as the vertical penetration by a borehole of a subsurface sequence - not all sequence components will be encountered. For example, when encountering the distal part of a sequence it is unlikely that any HST sediments will be observed. |
seqstrat_characterising.1679320149.txt.gz · Last modified: 20/03/2023 13:49 by mike_gss