User:WoodPig/sandbox

Building on Laurentia Article

My main goal for editing this article is to incorporate some key topics on Laurentia that are available but absent from this article.

After adding some sections and subsections I plan to broaden the lead section to reflect the additions.

Additional topics will include:

-Continental subduction and it's affects including enrichment of the mantle, (added to Tectonic setting)

-equatorial location, (New subtopic for Tectonic setting)

The equatorial location during the Late Ordovician period (480 to 430 Ma) on Laurentia has been determined via expansive shell bed records. Flooding of the continent that occured during the Ordovician provided the shallow warm waters for the success of sea life and therefor a spike in the carbonate shells of shellfish. Today the beds are composed of fossilized shells or massive-bedded Thalassinoidesfacies (MBTF) and loose shells or nonamalgamated brachiopod shell beds (NABS). These beds imply the presence of an equitorial climate belt that was hurricane free which lay inside 10° of the equator at 22.1°S ± 13.5°. This ecological conclusion matches the previous paleomagnetic findings which confirms this equatorial location.

New Section: "Paleoenvironmental change" "summarize the climates and history of vegetation (in general, as it reflects climate) on the land during the formation of Laurentia. This would be a sort of brief review of Phanerozoic climate change but limited to the Laurentian continent. So you would have a lot of wikilinks to articles such as Phanerozoic climate."

The last 541 million years.

The Phanerozoic climate of Laurentia is known to have several significant events. During the late Cambrian through the Ordovician, sea level fluctuated with with ice cap melt. Nine macro scale fluctuations of "Global hyper warming", or high intensity greenhouse gas conditions, occured. Due to sea level fluctuation, these intervals led to mudstone deposits on Laurentia that act as a record of events. The late Ordovician brought a cooling period, although the extent of this cooling is still debated. More than 100 Ma later, in the Permian, an overall warming trend occurred. As indicated by fossilized invertibrates, the western margin of Laurentia was affected by a lasting southward bound cool current. This current contrasted waters warming in the Texas region. This opposition suggests that during Permian global warm period, northern and northwest Pangea (western Laurentia) remained relatively cool.

Sources for Paleoenvironmental change:

Vegetation:

Climate:

Faunal evidence for a cool boundary current and decoupled regional climate cooling in the Permian of western Laurentia

Time-specific black mudstones and global hyperwarming on the Cambrian–Ordovician slope and shelf of the Laurentia palaeocontinent

Long-lived glaciation in the Late Ordovician? Isotopic and sequence-stratigraphic evidence from western Laurentia

Conodont apatite δ 18O values from a platform margin setting, Oklahoma, USA: Implications for initiation of Late Ordovician icehouse conditions

New sources:

-Chiarenzelli, J., Lupulescu, M., Cousens, B., Thern, E., Coffin, L., & Regan, S. (2010). Enriched Grenvillian lithospheric mantle as a consequence of long-lived subduction beneath Laurentia. Geology, 38(2), 151-154. (DOI: 10.1130/G30342.1 )

-Jin, J., Harper, D., Cocks, L., Mccausland, P., Rasmussen, C., & Sheehan, P. (2013). Precisely locating the Ordovician equator in Laurentia. Geology, 41(2), 107-110. (DOI: 10.1130/G33688.1)

-Jin, Harper, Rasmussen, & Sheehan. (2012). Late Ordovician massive-bedded Thalassinoides ichnofacies along the palaeoequator of Laurentia. Palaeogeography, Palaeoclimatology, Palaeoecology, 367-368, 73-88. (DOI: 10.1016/j.palaeo.2011.05.023)

-Landing, E. (2012). Time-specific black mudstones and global hyperwarming on the Cambrian–Ordovician slope and shelf of the Laurentia palaeocontinent. Palaeogeography, Palaeoclimatology, Palaeoecology, 367-368, 256-272. (DOI: 10.1016/j.palaeo.2011.09.005)