Galatia Channel:Hanover Limestone Member: Difference between revisions

From ILSTRAT
Jump to navigation Jump to search
No edit summary
 
(13 intermediate revisions by the same user not shown)
Line 1: Line 1:
{{Infobox links}}
{{Infobox_links/Stratigraphy}}
<center><div><ul>
<li style="display: inline-block;"> [[File:C605-Figure-04.jpg|thumb|left|500px|{{File:C605-Figure-04.jpg}}]]</li>
</ul></div></center>
==Hanover Limestone Member==
==Hanover Limestone Member==
The marine limestone member that directly overlies the Excello Shale is called the Hanover Limestone. The Hanover is regionally continuous but locally lenticular. In the deeper part of the basin, the Hanover ranges from fossiliferous shale a few inches (centimeters) thick to limestone averaging around 9.8 in. (25 cm) and rarely exceeding 19.7 in. (50 cm). The usual lithology is dark gray, very argillaceous, fossiliferous lime mudstone and wackestone. Fossils are chiefly brachiopods and echinoderm fragments, along with a few gastropods, bivalves, bryozoans, and ostracods. Shells are commonly unbroken and crinoid stems partly articulated, indicating low depositional energy. The rock may be massive or show indistinct, wavy banding of fossil fragments and shale laminae. On the western side of the basin, the Hanover tends to be thicker (locally more than 9.8 ft [3 m]) and the rock is lighter colored, is less argillaceous, and contains more diverse fossils. The contact with the Excello Shale may be sharp and wavy or gradational.   
The marine limestone member that directly overlies the Excello Shale is called the Hanover Limestone. The Hanover is regionally continuous but locally lenticular. In the deeper part of the basin, the Hanover ranges from fossiliferous shale a few inches (centimeters) thick to limestone averaging around 9.8 in. (25 cm) and rarely exceeding 19.7 in. (50 cm). The usual lithology is dark gray, very argillaceous, fossiliferous lime mudstone and wackestone. Fossils are chiefly brachiopods and echinoderm fragments, along with a few gastropods, bivalves, bryozoans, and ostracods. Shells are commonly unbroken and crinoid stems are partly articulated, indicating low depositional energy. The rock may be massive or show indistinct, wavy banding of fossil fragments and shale laminae. On the western side of the basin, the Hanover tends to be thicker (locally >9.8 ft [3 m]) and the rock is lighter colored, is less argillaceous, and contains more diverse fossils. The contact with the Excello Shale may be sharp and wavy or gradational.   


The Hanover and its fauna record a return to normal marine water circulation, with near-normal salinity and oxygen content. Bottom waters were intermittently agitated, likely below the normal wave base but within the storm wave base. Parts of the basin may have been too deep for carbonate production. Thicker and purer carbonate accumulated in shallower water on the Western Shelf. We interpret limestone deposition as occurring around highstand under a relatively dry, seasonal climate. Conversely, the switch from black shale to limestone might reflect stronger wind-driven circulation under climate otherwise unchanged (Cecil et al. 2003b).
The Hanover and its fauna record a return to normal marine water circulation, with near-normal salinity and oxygen content. Bottom waters were intermittently agitated, likely below the normal wave base but within the storm wave base. Parts of the basin may have been too deep for carbonate production. Thicker and purer carbonate accumulated in shallower water on the Western Shelf. We interpret limestone deposition as occurring around highstand under a relatively dry, seasonal climate. Conversely, the switch from black shale to limestone might reflect stronger wind-driven circulation under climate otherwise unchanged (Cecil et al. 2003b)<ref>Cecil, C.B., F.T., Dulong, R.R. West, R. Stamm, B. Wardlaw, and N.T. Edgar, 2003b, Climate controls on the stratigraphy of a Middle Pennsylvanian cyclothem in North America, in C.B. Cecil and N.T. Edgar, eds., Climate controls on stratigraphy: SEPM (Society for Sedimentary Geology) Special Publication 77, p. 151–180, https://doi.org/10.2110/pec.03.77.0151.</ref>.
==Additional Reading==
[[Hanover Limestone Member]] on ILSTRAT
{{Galatia Channel Page}}
{{Galatia Channel Page}}
[[Has parent page::Galatia_Channel:Stratigraphy| ]]
{{#set:Prev_Page=Galatia Channel:Excello Shale Member}}
{{#set:Next_Page=Galatia Channel:Delafield Member}}

Latest revision as of 20:49, 23 August 2023

  • Figure 4 Diagram showing units between the Houchin Creek and Herrin Coals, including members newly named in this report.

Hanover Limestone Member

The marine limestone member that directly overlies the Excello Shale is called the Hanover Limestone. The Hanover is regionally continuous but locally lenticular. In the deeper part of the basin, the Hanover ranges from fossiliferous shale a few inches (centimeters) thick to limestone averaging around 9.8 in. (25 cm) and rarely exceeding 19.7 in. (50 cm). The usual lithology is dark gray, very argillaceous, fossiliferous lime mudstone and wackestone. Fossils are chiefly brachiopods and echinoderm fragments, along with a few gastropods, bivalves, bryozoans, and ostracods. Shells are commonly unbroken and crinoid stems are partly articulated, indicating low depositional energy. The rock may be massive or show indistinct, wavy banding of fossil fragments and shale laminae. On the western side of the basin, the Hanover tends to be thicker (locally >9.8 ft [3 m]) and the rock is lighter colored, is less argillaceous, and contains more diverse fossils. The contact with the Excello Shale may be sharp and wavy or gradational.

The Hanover and its fauna record a return to normal marine water circulation, with near-normal salinity and oxygen content. Bottom waters were intermittently agitated, likely below the normal wave base but within the storm wave base. Parts of the basin may have been too deep for carbonate production. Thicker and purer carbonate accumulated in shallower water on the Western Shelf. We interpret limestone deposition as occurring around highstand under a relatively dry, seasonal climate. Conversely, the switch from black shale to limestone might reflect stronger wind-driven circulation under climate otherwise unchanged (Cecil et al. 2003b)[1].

Additional Reading

Hanover Limestone Member on ILSTRAT

Primary Source

Nelson, W.J., S.D. Elrick, W.A. DiMichele, and P.R. Ames, 2020, Evolution of a peat-contemporaneous channel: The Galatia channel, Middle Pennsylvanian, of the Illinois Basin: Illinois State Geological Survey, Circular 605, 85 p., 6 pls.

References

  1. Cecil, C.B., F.T., Dulong, R.R. West, R. Stamm, B. Wardlaw, and N.T. Edgar, 2003b, Climate controls on the stratigraphy of a Middle Pennsylvanian cyclothem in North America, in C.B. Cecil and N.T. Edgar, eds., Climate controls on stratigraphy: SEPM (Society for Sedimentary Geology) Special Publication 77, p. 151–180, https://doi.org/10.2110/pec.03.77.0151.