"Petrified algae"
In “right through the middle! and pet wood” at
http://lists.drizzle.com/pipermail/rockhounds_lists.drizzle.com/2013-February/000459.html
Tim Fisher wrote:
“I would like to see something concrete about the "petrified
algae". That has long been the explanation for the thick rind
around most of the limbs but I have never seen verification
of this.”
In addition, in “right through the middle! and pet wood” at
http://lists.drizzle.com/pipermail/rockhounds_lists.drizzle.com/2013-February/000462.html
Pete stated:
“I ditto, would be curious for some verified paleontological
information about the "petrified algae" too.”
I agree with Thomas Yancey’s objections to the term "petrified
algae" in his post "petrified algae" at
http://lists.drizzle.com/pipermail/rockhounds_lists.drizzle.com/2013-February/000464.html
I did a brief survey of a number of papers about the Green
River Formation. What is called "petrified algae" in previous
posts is often found in some members of it. In a few cases, it is
abundant enough in specific layers that they are recognizable
marker (key) beds within the Green River Formation. The
general terminology used to described the "petrified algae"
varies between “algal encrusted logs,” “algally encrusted logs,”
“tufa-encrusted logs,” and less commonly either “algal encrusted
tufa logs” or “algal-tufa-coated logs.” These logs are often
regarded to have formed within either shallow lake water or
mudflats associated with (forested) shorelines (Buchheim et al.
2011, Bradley 1926, McGrew 1980, McGrew and Casilliano
1975, Oriel and Tracey 1970, National Park service 1988,
Surdam 1979). Koernegay and Surdam (1980) simply state
that “The algal encrusted logs frequently represent a rapid
transgression into a wooded area.” However, the majority
of papers that mention encrusted logs typically lack any
discussion of specifically how the material encrusting them
formed. I suspect that some of the more laterally extensive
accumulations of carbonate encrusted logs, such as the
Blue Forest, might represent what sequence stratigraphers
call “transgressive surfaces.”
Although they do not provide much real detail, two papers,
Loewen et al (1990) and National Park Service (2012).
specifically describe the calcareous material encrusting logs
as consisting either of tufa, “stromatolite material,” or a
mixture of the two. Stromatolite material is defined as
“sediment trapped by cyanophytes (blue-green algae)” and
tufa as an inorganically precipitated crust of carbonate. They
regard the carbonate material encrusting some logs as having
formed as either an inorganic precipitate, as the result of
stromatolite formation for other logs, and for some logs as a
mixture of both organic and inorganic processes. They infer
that the formation of the carbonate crusts on logs required
the logs being submerged in place for a period of time.
Regardless of whether they are tufa, stromatolites, or mixture
of the two, I would not use the term “petrified” because these
crusts are quite likely primary carbonates that have not
been altered by later replacement.
Where these carbonate crusts lack laminations, they might
be properly considered to be thrombolities instead of
stromatolites. Where their origin is uncertain, a more
nongeneric terms, such as “micrite crust,” might be used.
Unfortunately I was not able to find any detailed studies
concerning the formation of the carbonate crusts found
encrusting logs within the Green River Formation. However,
a small detailed study was been made of quite similar
carbonate encrustations of silicified tree trunks in the basal
Purbeck Formation (Upper Jurassic) of southern England.
This study concluded that the encrusting carbonates were
created by microbial carbonate formation involving carbonate
grain trapping along with both the inorganic and organic
precipitation of carbonate. It regarded them as having the
typical features of freshwater tufa stromatolite deposits
(Clites 2005).
Tim Fisher also wrote:
“There are also "petrified termite mounds" just to the SW of
the Blue Forest area that I sincerely doubt are any remnant
of insect nests. I don't have any other explanation, other
than they look like the WY "fossil stromatolites" more than
anything else. Although I haven't seen anything definitive
about those either.”
Unfortunately, without some pictures, it is impossible to
definitively determine what these "petrified termite mounds"
might be. In case of the Green River Formation there are two
distinct possibilities as what they might be. First, as is
suggested above they might be stromatolites mistaken for
"petrified termite mounds." Finally, they might be caddisfly
mounds (bioherms), which occur within the Green River
Formation and form well defined beds and domal structures.
The figures in Leggitt et al. (2007) show fossil Caddisfly-
dominated microbial-carbonate mounds that would be
easy for people to misidentify as "petrified termite mounds."
Leggitt and Cushman (2001) also show caddisfly mounds
(bioherms) are quite similar in size and shape to termite
mounds. Their internal structure would readily be mistaken
for fossil termite mounds by the average lay person.
Fossil termite mounds and nest have been reported from
the Morrsion and Chinle formations of the American
Southwest (Hasiotis and Dubiel 1995, Hasiotis 2004); the
Lower Jurassic (Karoo Supergroup) of South Africa and
Lesotho (Bordy et al. 2009); and the Miocene of Chad
(Duringer et al. 2007). Thus, it is entirely possible that
fossil termite mounds might be found in the Green River
Formation.
Someone should compare the alleged "petrified termite
mounds" to what is published in Leggitt and Cushman
(2001), Leggitt et al. (2007), Hasiotis and Dubiel (1995),
Hasiotis (2004), Bordy et al. (2009), Duringer et al. (2007).
Also, the specific sedimentary facies, in which they are found,
will serve to clarify what they are as the reported fossil
termite mounds are all associated with strata and often
fossil soils that have been interpreted to be subaerial,
floodplain, natural levee, and eolian, in origin.
References Cited
Bordy, E. M., A. Bumby, O. Catuneanu, and P. G. Eriksson,
2009, Possible trace fossils of putative termite origin in the
Lower Jurassic (Karoo Supergroup) of South Africa and
Lesotho. South African Journal of Science. vol. 105,
pp. 356–362.
Buchheim, H. P., R. A. Cushman, Jr., and R. E. Biaggi, 2011,
Stratigraphic revision of the Green River Formation in Fossil
Basin, Wyoming: Overfilled to underfilled lake evolution.
Rocky Mountain Geology. vol. 46, no. 2, pp. 165-181,
Bradley, W. H., 1926, Shore phases of the Green River
Formation in northern Sweetwatt. County, Wyoming.
Professional Paper no. 140-D. U.S. Geological Survey,
Reston, Virginia. 11 pp.
Clives, E. C., 2005, “Burr” stromatolites in the basal Purbeck
Formation (Upper Jurassic of southern England). unpublished
Junior Independent Study paper, The College of Wooster,
Wooster, Ohio. 29 pp.
http://ismanual.voices.wooster.edu/files/2012/12/E_Clites1.pdf
(Also see “The fossil forest: part 1: The geology of the ledge.”
http://www.southampton.ac.uk/~imw/Fossil-Forest.htm and
http://www.southampton.ac.uk/~imw/Fossil-Forest-Purbeck-Trees.htm )
Duringer, P., M. Schuster, J. F. Genise, H. T. Mackaye, P.
Vignaud, and M. Brunet, 2007, New termite trace fossils:
galleries, nests and fungus combs from the Chad basin of
Africa (upper Miocene-Lower Pliocene). Palaeogeography,
Palaeoclimatology, Palaeoecology. vol. 251, no. 3-4,
pp. 323–353.
Hasiotis S. T., 2004, Reconnaissance of Upper Jurassic
Morrison Formation ichnofossils, Rocky Mountain region, USA:
Environmental, stratigraphic, and climatic significance of
terrestrial and freshwater ichnocoenoses. Sedimentary Geology.
vol. 167, no, 3-4, pp. 277–368.
Hasiotis, S. T., and R. F. Dubiel, 1995, Termite (Insecta: Isoptera)
nest ichnofossils from the Triassic Chinle Formation, Petrified
Forest National Park, Arizona. Ichnos. vol. 4, pp. 130–191.
Kornegay, G. L. and R. Surdam, 1980, The Laney Member of
the Green River Formation, Sand Wash Basin, Colorado, and
Its Relationship to Wyoming. in A. Harrison and others, eds.,
pp. 191-204, Stratigraphy of Wyoming : guidebook : 31st annual
field conference, Jackson Hole, Wyoming - Teton Village,
September 6-10, 1980, Wyoming Geological Association,
Casper, Wyoming.
Leggitt, V. M., and R. A. Cushman, 2001,Complex caddisfly-
dominated bioherms from the Eocene Green River
Formation. Sedimentary Geology. vol. 145, no. 3-4,
pp. 377-396.
Leggitt, V. M., R. E Biaggi, H P. Buchheim, 2007,
Palaeoenvironments associated with caddisfly-dominated
microbial-carbonate mounds from the Tipton Shale Member
of the Green River Formation: Eocene Lake Gosiute.
Sedimentology. vol. 54, no. 3, pp.661–699.
Loewen, M. A., V. L. Leggit and H. P. Buchheim, 1990, Caddisfly
(Trichoptera) larval cases from Eocene Fossil Lake. National
Park Service Paleontological Research. no. 4, pp. 72-22.
(Geologic Resources Division Technical Report no.
NPS/NRGRD/GRDTR-99/03)
McGrew, P. O., 1980, An Eocene flamingo nesting area,
Sweetwater County, Wyoming. National Geographic Society
Research Reports. vol. 12, pp. 473–478.
McGrew, P. O., and M. Casilliano, 1975, The geological history
of Fossil Butte National Monument and Fossil Basin. Occasional
Paper no. 3, National Park Service, Washington, D.C.
National Park service, 2012, Fossil Butte National Monument:
Geologic Resources Inventory Report. Natural Resource
Report NPS/NRSS/GRD/NRR—2012/587, U.S. Department of the
Interior, Washington, D.C. 53 pp.
Oriel, S. S., and J. I. Tracey, Jr., 1970, Uppermost Cretaceous
and Tertiary stratigraphy of Fossil Basin, southwestern
Wyoming. Professional Paper no. 635. U.S. Geological Survey,
Reston, Virginia. 53 pp.
Yours,
Paul H.
