free hit counter Visitors to these pages since 12-29-97
|"Two thirds of the Haymond is
composed of a repetitious alternation of fine- and very fine-grained olive
brown sandstone and black shale in beds from a millimeter to 5 cm thick.
The formation is estimated to have more than 15,000 sandstone beds greater
than 5 mm thick." p. 87.
A famous outcrop of the Haymond is seen below from Earl F. McBride, "Sedimentary Petrology and History of the Haymond Formation (Pennsylvanian), Marathon Basin, Texas," Bureau of Economic Geology, Report on Investigations 57, 1966, Plate 3a. It shows the highly laminated nature of the flysch facies and the clean separation of the sands and the shales.
The sands are described by McBride:
“Quartz is the most abundant framework constituent in all sandstones; it ranges from 57 to 80 percent and averages 67 percent.” Earle F. McBride, “Sedimentary Petrology and History of the Haymond Formation (Pennsylvanian), Marathon Basin, Texas,” Bureau of Economic Geology, The University of Texas, Report of Investigations—57, (March 1966), p.31
The evidence supports the idea that these rocks were deposited in deepwater:
“The interpretation that the Haymond Flysch sediments accumulated in deep water is based on (a) the presence of quiet-water muds (shales), (b) the lack of textures or structures that form only in shallow-water environments, such as large-scale cross-beds, mud cracks, wave ripple marks, etc., and (c) the absence of shallow-water fossils in the shales—land plant fragments can float, and mud-burrowing animals have been found in modern oceans at abyssal depths. The latter two lines of reasoning imply negative evidence, but they are important aspects where no reliable faunal depth indicators are present.” Earle F. McBride, “Sedimentary Petrology and History of the Haymond Formation (Pennsylvanian), Marathon Basin, Texas,” Bureau of Economic Geology, The University of Texas, Report of Investigations—57, (March 1966), p. 45
These burrows are seen in McBride's 1966 Bureau of Economic Geology, Report on Investigations 57, Plate 13A. It is modified from that publication below:
The burrow on the right shows a line of sand particles filling the burrow (the dog-legged line of white.. The burrow on the left is mostly shale filled. The diagonal lines are the saw marks.
But there are other types of burrows in the Haymond. These are horizontal burrows seen below:
And as seen above, there are horizontal burrows which certainly are not escape structures.
The Haymond also has some boulder beds which have yielded up some limestone conglomerates which are interesting: Palmer et al wrote:
“In 1982, DeMis noted rare limestone boulders in a previously
unmapped conglomerate unit within the Haymond Formation. This unit forms
part of a 6.5-km-long dip slope in the stratigraphically highest part of
the Haymond Formation exposed beneath the Hell’s Half Acre thrust fault.
The unit is composed largely of chert pebbles in a sand-shale matrix, but
scattered through the unit in several different graded beds are rare
boulders of chert and limestone 10-60 cm in diameter.
limestone boulders are so unusual in the largely siliciclastic Haymond
Formation, DeMis collected three small limestone boulders. One boulder
yielded several genera of Middle Cambrian phosphatic brachiopods and many
trilobites. Nearly all of the trilobite and brachiopod taxa in that
boulder were previously described from the Marjum Formation in western
Utah and represent the late Middle Cambrian Bolaspidella Zone. The
other two boulders also
yielded trilobites and phosphatic brachiopods of the Bolaspidella
Zone. Seven more boulders were collected during a short visit to the 0.5
km2 discovery area in January 1983.” Alison R. Palmer, et al,
“Geological Implications of Middle Cambrian Boulders from the Haymond
Formation (Pennsylvanian) in the Marathon Basin, West Texas,” Geology,
12(1984):91-94, p. 91
These trilobites did not come from Utah because the Haymond formation was deposited from the southeast. We know that these limestone rocks were not originally deposited in the Haymond because the Haymond doesn't have any limestone except for these cobbles which were rounded having been washed into place. Indeed large quantities of sand and shale inhibit the growth of limestone depositing organisms. One can see beautiful limestone beaches around Florida and the Bahamas but none anywhere near the Mississippi River which puts out so much muck that most limestone depositing organisms can't survive the muddly waters.
The sequence of events seen above is as follows::
Trilobites buried and cemented into a limestone southeast of the Haymond
Limestone rocks are later eroded
Cobbles move down river
Eventually deposited in the Haymond formation
However, the trilobites were already fossilized when they were ripped up and re deposited in the Haymond formation. Below are pictures of these already fossilized trilobites in the Pennsylvanian.
Notice that these trilobits show signs of wear and decay prior to their entombment. That means that there was some time span between their death and their dismemberment prior to burial.
Back to DMD Publishing Home Page