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Compiled by: Jacques LeBlanc (2021), Stratigraphic Lexicon: The Onshore Cenozoic Sedimentary Formations of The Republic of Panama. Biosis: Biological Systems, vol. 2/1, 1-173. https://doi.org/10.37819/biosis.002.01.0095(or via https://sites.google.com/site/leblancjacques).

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Atlantic Muck Formation
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Atlantic Muck Fm base reconstruction

Atlantic Muck Fm

Period: 
Quaternary

Age Interval: 
Pleistocene to Recent (0.13 Ma) - Woodring (1960); Hendy (2014)


Province: 
Panama Canal basin

Type Locality and Naming

The following description is as valid for the Atlantic Muck as for the Pacific Muck: MacDonald (1913a, 1913b, 1915) observed “extensive unconsolidated deposits of black, organic-rich marine mud with horizontal bedding” but does not name them. Thompson (1943, 1947) named them and described them as “Heterogeneous mixture of alluvially deposited silts, clays, and carbonaceous material within which are beds of marine origin containing Pleistocene and early Recent forms of mollusks and corals”.

Synonym: Mount Hope Fm; Pacific Muck


Lithology and Thickness

MacDonald (1913a, 1913b, 1915) divides the muck into four phases. The lower phase, adjacent to its contact with older formations, consists of grey to bluegrey silty clay. The phase deposited in brackish marine waters contains abundant mollusk shells in an organic, black-silt matrix. The littoral swamp deposit is composed of semi-decayed wood and other organic vegetable matter, intermixed with silt and is characteristically dark brown to black. A soft, light-grey, weak, plastic clay overlies the organic phase. The four phases intergrade, with sand lenses locally present. The muck was deposited upon a stream-eroded topography of considerable relief. Old core borings reveal depths of over 200 feet for this deposit. Hills of the Gatún Fm protrude thru the black muck and in the area south of Gatún these hills form islands that are completely surrounded by the swamp muck deposits.

Jones S.M. (Sept 1950). Pleistocene and Recent formation consisting of swamp deposits, both alluvial and marine, largely composed of clays, silts, and fine sands irregularly intermixed, uniformly soft and weak, and having a very high moisture content. Observation of drill cores throughout the Gatún Lake area indicates that Thompson (1943)'s four phases of the Muck are present in all thick muck deposits. In addition, the top and bottom phases appear to be thinnest and most widespread; the two middle phases are much the thickest, form the bulk of the formation, and interfinger so extensively that individual drill holes may show interbedding of these two phases. The brackish marine phase is north, or downstream from the littoral swamp phase and inter-fingers seaward with extensive beds of unconsolidated finger- and brain-coral fragments north of Gatún.


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

Upper contact

N/A

Regional extent

Present on Atlantic side of Panama Canal.


GeoJSON

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Fossils

Brain-coral fragments


Age 


Age Span: 

    Beginning stage: 
Chibanian

    Fraction up in beginning stage: 
0

    Beginning date (Ma): 
0.77

    Ending stage: 
Holocene

    Fraction up in the ending stage: 
1

    Ending date (Ma):  
0.00

Depositional setting

swamp deposits, both alluvial and marine,


Depositional pattern:  


Additional Information

References:

  • MacDonald (1913a, 1913b, 1915)
  • Jones S.M. (Sept 1950).
  • Thompson (1943)
  • Wilson et al. (1957).
  • Woodring (1960). Informal name for swamp, stream, and marine Pleistocene deposits on the Caribbean, or Atlantic, side of the Canal Zone. Marine deposits contain numerous species of mollusks, nearly all of which are Recent. Brown and Pilsbry (1913)
  • Keroher et al. (1966); Kirby (2006); Hendy (2014); Redwood (2020).


Compiler:  

Jacques LeBlanc (2021), Stratigraphic Lexicon: The Onshore Cenozoic Sedimentary Formations of The Republic of Panama. Biosis: Biological Systems, 2(1), 173 pp. https://doi.org/10.37819/biosis.002.01.0095 (or via https://sites.google.com/site/leblancjacques)