Blackberry Hill

Blackberry Hill
Stratigraphic range: Cambrian
Location
Region Wisconsin
Country United States
Type section
Named for Topographic feature (a summit) in Marathon County

Blackberry Hill is a series of quarries and outcrops in Central Wisconsin that is notable for its large concentration of trace fossils in Cambrian rocks. One quarry in particular, located in Marathon County, also has the distinction of preserving some of the first land animals. The site is a prolific Cambrian Konservat-Lagerstätte. It includes three-dimensional casts[1] of soft bodied and lightly scleritized invertebrates and a variety of exceptionally preserved types of trace fossils.

Age and stratigraphic placement

The strata at Blackberry Hill are known to belong to the Elk Mound Group;[2][3] however, the lack of good stratigraphic markers (i.e., index fossils) in some Blackberry Hill localities, coupled with uncertainties about the age range of the Elk Mound Group itself, make it difficult to assign a precise age to these strata. Many researchers consider these rocks to be Late Cambrian,[3][4] which is the age to which the Elk Mound Group was originally assigned;[5] however, some recent authors now believe the Elk Mound Group and the fossils of Blackberry Hill could date back to the Middle Cambrian, based on certain fossils obtained from other areas.[6][7]

Geological and environmental setting

Most of the strata are composed of well bedded quartz sandstone and orthoquartzite. They were deposited mainly on intertidal and supratidal sand flats along the southern shoreline of the supercontinent Laurentia.[8] Ripple marks and numerous other sedimentary structures identical to those found on modern beaches abound on the strata surfaces. One of the most conspicuous features is extensive areas of specific structures not unlike those associated with modern biofilms and microbial mats.[3] There is mounting evidence suggesting that the feeding potential of this presumed microbial material was one of the forces that lured the first animals out of the sea.[9] It is also believed that the same material aided in the exceptional preservation of many of Blackberry Hill’s trace fossils.[8][10][11]

Ripple marks are exceptionally distinct on the surfaces of many layers at Blackberry Hill. 
Sand stromatolites, such as these encrusting a ripple marked surface, are common sedimentary structures associated with microbial activity. 

Significance

Among the many paleontological discoveries thus far made at Blackberry Hill are the following:

The largest, most productive quarry is still in operation, thereby revealing fresh surfaces and the potential for new discoveries on a continuing basis.

Biota

Sedimentary structures associated with biofilms and microbial mats [3] are the only evidence of non-animal life at Blackberry Hill, as is the case elsewhere in this pre-embryophyte period in the history of Earth’s life on land. The animal life of Blackberry Hill was, however, represented by several kinds of macrofossils, all preserved as three-dimensional casts or impressions,[1] including:

Mosineia macnaughtoni, the presumed maker of some of the Protichnites and Diplichnites trackways at Blackberry Hill. The rock section shown in this photograph is about 13 cm long. 
Carapace of the phyllocarid, Arenosicaris inflata. Splayed carapace is about 3 cm wide across both valves. 
Stranded scyphozoans (jellyfish) in a partially flooded quarry. Due to the flat, horizontal bedding at this quarry, the scyphozoans shown in the background in the top/right photo are seen protruding above the water's surface. 

Trace fossils

Protichnites trackways with particularly distinct medial furrows. Distinctness of the furrows is believed to be influenced by environmental and substrate conditions. 
Diplichnites trackway, possibly an undertrack. 
Climactichnites wilsoni, the surface trackways from a large, slug-like mollusk. In this sprawling example, the many trackways are seen overlapping each other. These examples are about 10 cm wide. 
Cruziana-like traces, possibly from the phyllocarid Arenosicaris inflata. 

References

  1. 1 2 3 4 5 6 7 8 Collette and Hagadorn, 2010
  2. 1 2 3 Hagadorn et al., 2002
  3. 1 2 3 4 Schieber et al., 2007
  4. 1 2 3 4 Getty and Hagadorn, 2008
  5. Ostrom, 1966
  6. Seilacher and Hagadorn, 2010
  7. 1 2 Young and Hagadorn, 2010
  8. 1 2 3 4 5 6 7 8 Collette et al., 2012
  9. MacNaughton et al., 2002
  10. Seilacher, 2007, page 28
  11. Seilacher, 2008
  12. Hagadorn and Belt, 2008, page 429
  13. Owen, 1852
  14. 1 2 Hagadorn and Seilacher, 2009
  15. Goldring and Seilacher, 1971
  16. Hoxie, 2005
  17. 1 2 Yochelson and Fedonkin, 1993
  18. 1 2 Getty and Hagadorn, 2009
  19. Collette et al, 2010

Further reading

  • Collette, J. H., K. C. Gass, & J. W. Hagadorn (2012). "Protichnites eremita unshelled? Experimental model-based neoichnology and new evidence for a euthycarcinoid affinity for this ichnospecies". Journal of Paleontology 86 (3): 442–454. doi:10.1666/11-056.1. 
  • Collette, J. H. and J. W. Hagadorn (2010). "Three-dimensionally preserved arthropods from Cambrian Lagerstatten of Quebec and Wisconsin". Journal of Paleontology 84 (4): 646–667. doi:10.1666/09-075.1. 
  • Collette, J. H., J. W. Hagadorn, and M. A. LaCelle (2010). "Dead in their tracks: Cambrian arthropods and their traces from intertidal sandstones of Quebec and Wisconsin". PALAIOS 25 (8): 475–486. doi:10.2110/palo.2009.p09-134r. 
  • Getty, P. R., and J. W. Hagadorn (2008). "Reinterpretation of Climactichnites Logan 1860 to include subsurface burrows, and erection of Musculopodus for resting traces of the trailmaker". Journal of Paleontology 82 (6): 1161–1172. doi:10.1666/08-004.1. 
  • Getty, P. R., and J. W. Hagadorn (2009). "Palaeobiology of the Climactichnites tracemaker". Palaeontology 52 (4): 753–778. doi:10.1111/j.1475-4983.2009.00875.x. 
  • Goldring, R., and A. Seilacher (1971). "Limulid undertracks and their sedimentological implications". Neues Jarbuch fur Geologie und Palaontologie Abhandlungen 137: 422–442. 
  • Hagadorn, J. W. and E. S. Belt (2008). "Stranded in upstate New York: Cambrian scyphomedusae from the Potsdam Sandstone". PALAIOS 23 (7): 424–441. doi:10.2110/palo.2006.p06-104r. 
  • Hagadorn, J. W., R. H. Dott, and D. Damrow (2002). "Stranded on an Upper Cambrian Shoreline: Medusae from Central Wisconsin". Geology 30 (2): 147–150. doi:10.1130/0091-7613(2002)030<0147:SOALCS>2.0.CO;2. 
  • Hagadorn, J. W., and A. Seilacher (2009). "Hermit arthropods 500 million years ago?". Geology 37 (4): 295–298. doi:10.1130/G25181A.1. 
  • Hoxie, C. T. (2005). "Late Cambrian arthropod trackways in subaerially exposed environments: Incentives to simplify a problematic ichnogenus". Unpublished B.A. Thesis: 1–89. 
  • MacNaughton, R. B., J. M. Cole, R. W. Dalrymple, S. J. Braddy, D. E. G. Briggs, and T. D. Lukie (2002). "First steps on land:Arthropod trackways in Cambrian-Ordovician eolian sandstones, Canada". Geology 30 (5): 391–394. doi:10.1130/0091-7613(2002)030<0391:FSOLAT>2.0.CO;2. 
  • Ortega-Hernandez, J., Tremewan, J., and Braddy, S. J. (2010). "Euthycarcinoids". Geology Today 26 (5): 195–198. doi:10.1111/j.1365-2451.2010.00770.x. 
  • Ostrom, M. E. (1966). Cambrian Stratigraphy of Western Wisconsin. Wisconsin Geological and Natural History Survey. 
  • Owen, R. (1852). "Description of the impressions and footprints of the Protichnites from the Potsdam sandstone of Canada". Geological Society of London Quarterly Journal 8: 214–225. doi:10.1144/GSL.JGS.1852.008.01-02.26. 
  • Schieber, J.; Bose, P. K.; Eriksson, P. G.; Banerjee, S.; Sarkar, S.; Altermann, W.; Catuneau, O. (2007). Atlas of Microbial Mat Features Preserved within the Clastic Rock Record. Elsevier. pp. 53–71. 
  • Seilacher, A. (2007). Trace Fossil Analysis. New York, New York: Springer. p. 226. 
  • Seilacher, A. (2008). "Biomats, biofilms, and bioglue as preservational agents for arthropod trackways". Palaeogeography, Palaeoclimatology, Palaeoecology 270 (3–4): 252–257. doi:10.1016/j.palaeo.2008.07.011. 
  • Seilacher, A. and J. W. Hagadorn (2010). "Early molluscan evolution: Evidence from the trace fossil record". PALAIOS 25 (9): 565–575. doi:10.2110/palo.2009.p09-079r. 
  • Yochelson, E. L. and M. A. Fedonkin (1993). "Paleobiology of Climactichnites, an enigmatic Late Cambrian fossil". Smithsonian Contributions to Paleobiology 74: 1–74. doi:10.5479/si.00810266.74.1. 
  • Young, G. A. and J. W. Hagadorn (2010). "The fossil record of cnidarian medusa". Palaeoworld 19 (3–4): 212–221. doi:10.1016/j.palwor.2010.09.014. 

External links

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