Galatia Channel:Rapid Transgression, Gradual Regression

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Rapid Transgression, Gradual Regression

Evidence from the Pleistocene, particularly the most recent deglaciation, indicates that melting can be surprisingly rapid, even “catastrophic.” Blanchon and Shaw (1995, p. 4)[1] inferred, based on drowned reefs in the Caribbean and Gulf of Mexico, “three catastrophic, metrescale sea-level–rise events during the last [Pleistocene] deglaciation.” Gregoire et al. (2012)[2] calculated that a sea-level rise of 45.9 to 59.0 ft (14 to 18 m) took place within a span of about 350 years close to 14,000 years ago, and a rise of 29.5 ft (9 m) took place within 500 years about 8,200 years ago. Data from Greenland ice cores indicate two remarkably sudden Late Pleistocene warming events. One at 11,700 years B.P. lasted 60 years, and an earlier event at 14,700 years ago spanned a mere 3 years (Steffensen et al. 2008)[3]. Other evidence and examples may be found in Webster et al. (2004)[4], Wright et al. (2009)[5], Bird et al. (2010)[6], and Törnqvist and Hijma (2012)[7]. In contrast, the growth of a continental ice cap requires a much longer interval of time, measured in thousands to tens of thousands of years (Muhs et al. 2011[8]; Dutton and Lambeck 2012[9]).

The authors cited above suggest that any triggering event that raises the sea level may set off a chain of events leading to the rapid destruction of ice caps. The trigger could be the onset of a warmer climate or the failure of ice dams that hold back large bodies of fresh water, such as glacial Lake Agassiz and Lake Missoula. The rising sea breaks up floating ice sheets and releases fleets of icebergs, which melt in warmer waters and raise the sea level further. Moreover, the loss of sea ice changes the ocean and atmospheric circulation, leading to more melting. In contrast, the growth of continental glaciers is “glacially slow” because snow and ice can accumulate only so fast. In fact, the global cooling required to bring on an ice age reduces the capacity of the atmosphere to hold water vapor and yield snow.

The rapid drowning and burial of the Springfield peat swamp has counterparts in other late Paleozoic deposits. Ravinement surfaces are reported from other coals, such as the Herrin Coal of Illinois (DeMaris et al. 1983)[10], which also has a buried autochthonous flora adjacent to the Walshville paleochannel (DiMichele and DeMaris 1987)[11]. Lower Permian carbonate cycles of Kansas commonly begin with a thin transgressive lag of fish bones, ostracods, and intraclasts, implying abrupt, erosive transgression (Miller et al. 1996)[12]. The rapid marine transgression that terminated peat accumulation repeats throughout the Pennsylvanian in the Illinois Basin among coal beds that lack channels and a gray shale roof. Most commonly, the coal is sharply overlain either by offshore black, phosphatic black shale or by marine limestone; at the contact, coal laminations are generally truncated, indicating some erosion of the top of the peat body. At the base of black shale, a thin pyritic shell breccia may be present (Zangerl and Richardson 1963)[13]. Where nonmarine gray shale overlies low-sulfur coal, in situ tree stumps and tidal rhythmites are commonly in evidence. We have logged examples, including the Lower Block, Murphysboro, Colchester, Herrin, and Danville Coals in addition to the Springfield.

Conditions of rapid, pulse-like sea-level rises likely also occurred during the Pennsylvanian ice age (Archer et al. 2016)[14]. Such considerations further militate against the notion of “keep up” time-transgressive peat swamps created by rising base level and driven across the landscape by sea-level rise (e.g., Heckel 1995)[15]. Peat formed much too slowly to keep up with the abrupt sea-level rise of a typical deglaciation.

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. Blanchon, P., and J. Shaw, 1995, Reef drowning during the last deglaciation: Evidence for catastrophic sea-level rise and ice-sheet collapse: Geology, v. 23, no. 1, p. 4–8.
  2. Gregoire, L.J., A.J. Payne, and P.J. Valdes, 2012, Deglacial rapid sea level rises caused by ice-sheet saddle collapses: Nature, v. 487, p. 219–22.
  3. Steffensen, J.P., K.K. Andersen, M. Bigler, H.B. Clausen, D. Dahl-Jensen, H. Fischer, K. Goto-Azuma, M. Hansson, S.J. Johnsen, J. Jouzel, V. Masson-Delmotte, T. Popp, S.O. Rasmussen, R. Röthlisberger, U. Ruth, B. Stauffer, M.-L. Siggaard-Andersen, Á.E. Sveinbjörnsdóttir, A. Svensson, and J.W.C. White, 2008, High-resolution Greenland ice core data show abrupt climate change happens in a few years: Science, v. 321, p. 680–683.
  4. Webster, J.M., D.A. Clague, K. Riker-Coleman, C. Gallup, J.C. Braga, D. Potts, J.G. Moore, E.L. Winterer, and C.K. Paull, 2004, Drowning of the 150-m reef in Hawaii: A casualty of global meltwater pulse 1A?: Geology, v. 32, p. 249–252.
  5. Wright, J.D., R.E. Sheridan, K.G. Miller, J. Uptegrove, B.S. Cramer, and J.V. Browning, 2009, Late Pleistocene sea level on the New Jersey margin: Implications to eustasy and deep-sea temperature: Global and Planetary Change, v. 66, p. 93–99.
  6. Bird, M.I., W.E.N. Austin, C.M. Wurster, L.K. Fifield, M. Mojtahid, and C. Sargeant, 2010, Punctuated sea-level rise in the early mid-Holocene: Geology, v. 38, p. 803–806.
  7. Törnqvist, T.E., and M.P. Hijma, 2012, Links between early Holocene icesheet decay, sea-level rise and abrupt climate change: Nature Geoscience, v. 5, p. 601–606.
  8. Muhs, D.R., K.R. Simmons, R.R. Schumann, and R.B. Halley, 2011, Sea-level history of the past two interglacial periods: New evidence from U-series dating of reef corals from south Florida: Quaternary Science Reviews, v. 30, p. 570–590.
  9. Dutton, A., and K. Lambeck, 2012, Ice volume and sea level during the last interglacial: Science, v. 337, p. 216–219.
  10. DeMaris, P.J., R.A. Bauer, R.A. Cahill, and H.H. Damberger, 1983, Geologic investigation of roof and floor strata, longwall demonstration, Old Ben Nine No. 24, prediction of coal balls in the Herrin Coal: Illinois State Geological Survey, Contract/Grant Report 1983-2, 69 p.
  11. DiMichele, W.A., and P.J. DeMaris, 1987, Structure and dynamics of a Pennsylvanian-age Lepidodendron forest: Colonizers of a disturbed swamp habitat in the Herrin (No. 6) Coal of Illinois: Palaios, v. 2, p. 146–157.
  12. Miller, K.B., T.J. McCahon, and R.R. West, 1996, Lower Permian (Wolfcampian) paleosol-bearing cycles of the U.S. Midcontinent: Evidence of climatic cyclicity: Journal of Sedimentary Research, v. 66, no. 1, p. 71–84.
  13. Zangerl, R., and E.S. Richardson, 1963, Paleoecological history of two Pennsylvanian black shales: Fieldiana (Field Museum, Chicago), Geological Memoir 4, 352 p.
  14. Archer, A.W., S. Elrick, W.J. Nelson, and W.A. DiMichele, 2016, Cataclysmic burial of Pennsylvanian Period coal swamps in the Illinois Basin: Hypertidal sedimentation during Gondwanan glacial melt-water pulses, in B. Tessier and J.-Y. Reynaud, eds., Contributions to modern and ancient tidal sedimentology: Proceedings of the Tidalites 2012 Conference: International Association of Sedimentologists, Special Publication 48, p. 217–231.
  15. Heckel, P.H., 1995, Glacial-eustatic base-level climatic model for late Middle to Late Pennsylvanian coal-bed formation in the Appalachian basin: Journal of Sedimentary Research, v. B65, no. 3, p. 348–356.