Marissa Pitter, “Unearthing the Unknown: the Fossils of The

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Unearthing the Unknown: The Fossils of the Budden Collection

Marissa Pitter

In the South Gallery Room of the L.C. Bates Museum sit eight fossil display cases. In the cramped sixth case rests a significant fossil, the Pertica quadrifaria—Maine’s state fossil which comes from the rocks of the world-renowned Trout Valley Formation. Alongside the rare fossilized remains of Pertica lies “The Budden Collection,” a group of seven fossils found in northern Maine and donated to the museum in 2013. A label sits below each fossil identifying the name of the specimen (and at times, its genus and species), the geologic period and 2 formation, and the location where the fossil was found. The exact descriptions that the L.C.

Bates Museum provides on the labels is given in Table 1.

Table 1. The Budden Collection Fossils

Fossil Geologic Period Geologic Formation Location

Favositid Coral (1) Silurian Hardwood Mountain Hobbstown Township, Maine

Favositid Coral (2) Silurian Hardwood Mountain Hobbstown Township, Maine

Horn coral with trace Devonian Seboomook Tomhegan Township, fossils Maine

Rugose Coral Ordovician/Silurian Formation Unknown Shin Pond, Maine

Brachiopod Devonian Seboomook Tomhegan Township, Mucrospirifer? Maine

Brachiopods likely Devonian Formation Unknown Big Moose Township, steinkerns (fossilized Maine outlines)

Leptostrophia and Devonian likely Seboomook Big Moose Township, Tentaculites Maine

The question mark following “Mucrospirifer,” the unknown geologic formations, and the impreciseness of the geologic age of the rugose coral indicate there are some uncertainties among the museum’s identifications. The table also points to some commonalities among the fossil collection. Besides the fact that all the fossils are from northern Maine, the Budden

Collection is comprised of corals and brachiopods from either the Silurian or Devonian Periods.

On the other side of the South Gallery Room is an enlarged, framed geologic time scale (fig. 2), listing Earth’s geological eras and periods, and noting major events. Maine’s fossil record dates back to the Paleozoic Era and contains rocks from the Cambrian, Ordovician, Silurian, and

Devonian Periods, but the state’s geological history is complex (“Fossils”). This complexity is 3 situated within the bedrock pattern, produced by a cycle of geologic processes “including erosion and sedimentation, mountain-building, deformation (folding and faulting), metamorphism, and igneous activity” (Marvinney). These processes played a role in removing records of geological history, thus contributing to the over 300-million-year gap in Maine’s fossil record (“Fossils”).

Similarly to the Budden Collection, there are some unknowns about Maine’s geology, but geologic investigations and field work conducted with the aim to produce new information should lead to a better understanding of the state’s bedrock. Relying on studies of Maine’s geology, this paper seeks to unearth what the geological history of Maine could imply about the unknowns in the L.C Bates Museum’s Budden Collection.

Fig. 3. Map of Earth’s tectonic plates during Late Ordovician Period. [Maine’s Fossil Record]

Fig. 4. Map showing the modern location of plate fragments and inferred origin of Maine rocks. [Maine’s Fossil Record]

In order to understand the landmass that we now call the State of Maine, focus must be geared towards how Earth’s tectonic plates evolved to assemble Maine’s bedrock foundation. Of importance to the formation of Maine’s bedrock is the collision and accretion of the microcontinent Avalonia to the continent of Laurentia (Dickson 26; fig. 3). Rocks that are now in 5 northern Maine were deposited along the southern coast of Laurentia during the Late Ordovician

Period (fig. 4). By the Late Devonian Period, Laurentia and Avalonia collided, creating a range of mountains which included the rocks that were originally deposited during the Ordovician and

Silurian Periods. The welding of Laurentia to Avalonia—along with other microcontinents, plate fragments, and volcanic arcs—created Laurussia, one of the major continents alongside

Gondwana. Paleontologists believe that most of Maine’s fossils come from this period of the

Devonian when there were two major continents (“Dinosaurs”). This deduction is based on the fact that by this geological period, the framework of Maine’s bedrock had been assembled. It also could serve as an explanation for why the majority of the fossils in the Budden Collection are from the Devonian Period.

The Devonian Period in Maine was characterized by brachiopods. Of the thirty-eight deposits during this geologic time period, twenty-six were dominated by brachiopods (Dickson 288).

Furthermore, one hundred and seventeen different brachiopod genera have been recorded from the Devonian (Dickson). Brachiopods are speciose fossils and their diversity can be acknowledged within museums based on the information a museum discloses through its labelling. Three of the four Devonian-age fossils within the Budden Collection are brachiopods, and two have labels recording their genera. On one label, the scientific name for the brachiopod

Mucrospirifer (fig. 5) ends with a question mark, the notation indicating there is uncertainty regarding the organism’s genus (Dickson 45). Mucrospirifers are nicknamed “butterfly shells” due to its wide and winged-like appearance and are accompanied with a long hinge line that ends with mucronate points. Two Mucrospirifers found in Somerset County, Maine, possess a

“transverse, triangular outline, about twice as broad as long” and a “sub-pyramidal shape”; 6 additional external details could not be described due to the specimens poor preservation

(Boucot, “Earl Moose” 60). It is of interest whether the condition of the Mucrospirifer in the

L.C. Bates Museum attributed to the uncertainty in its identification. Three fossils to the right of the Mucrospirifer sits another label that identifies the genera of two specimens contained in the same rock: Leptostrophia, a brachiopod, and Tentaculites, about which very little is known but which is usually classified as a type of mollusk. Unlike the Mucrospirifer, both genera are recorded on the label without the use of a question mark; however, the label also notes that the fossil is likely from the Seboomook Formation, indicating that the museum cannot definitively state what geologic formation these specimens came from. Data indicates that the Leptostrophia species, such as specimens of the Leptostrophia cf. L. magnifica, were often found in the

Seboomook and Tarratine Formations (Kite and Kammer 103). The Tarratine Formation is said to be the shallow-water equivalent to the deep-water marine deposits of the Seboomook

Formation, and brachiopods, like Leptostrophia, survived in both shallow water and deep water settings (Heath 30–31); therefore, it would be probable that the Leptostrophia species would occur among both formations. On the other hand, tentaculitoids—according to the genera that have been identified in Maine—seem to have existed mostly in shallow water deposits (Dickson

175). It would explain why Tentaculites were contained in the Devonian-aged rocks of the

Tarratine Formation (Heath 29). Could these findings suggest that the Leptostrophia and

Tentaculites fossil originated from the Tarratine instead of the Seboomook? 7

Fig. 5. Brachiopod Mucrospirifer? Hinckley, Maine: L.C. Bates Museum. [Staber]

The Seboomook Formation has significant areal coverage in northern Maine. Three of the

Budden Collection fossils are claimed to be from the Seboomook Formation. However, it should be noted that the majority of fossils recovered from this formation possibly did not form there.

Boucot (“Stratigraphy” 170) claims that nearly all of the fossils he recovered in the Seboomook were about a mile away from the Tarratine Formation; the Tarratine and Seboomook Formations integrate with each other and species found in the Tarratine resemble those in the Seboomook

(Kite and Kammer 103). Bearing this information in mind, questions may arise about whether the Budden Collection’s fossils from the Seboomook were once present in the Tarratine— particularly the brachiopod and horn coral with trace fossils that were both recovered in

Tomhegan Township, which is in close proximity to the Tarratine. 8

Fig. 6. Horn coral with trace fossils. Hinckley, Maine: L.C. Bates Museum. [Staber]

Fig. 7. Rugose Coral. Hinckley, Maine: L.C. Bates Museum. [Staber]

Recall that three of the four Devonian-age fossils in the Budden Collection are brachiopods. The fourth fossil from this geologic age is the horn coral with trace fossils (fig. 6). Although brachiopods were dominant among Devonian-aged deposits, corals were common, as well, due 9 to the shallow water environments (Dickson 51). The Silurian Period was characterized by shallow marine settings that continued into the Devonian (Dickson 243). This environment may serve as one explanation for why the Budden’s horn coral is preserved from this time period.

Another horn coral exists in the Budden Collection, but it is referred to as a rugose coral (fig. 7).

According to Table 1, the rugose coral misses some identifying markers; the coral is assumed to be of either Ordovician or Silurian age and the geologic formation is unknown. Shallow water settings were scarce during the Ordovician Period and it is because of this scarcity that corals were uncommon during this time, with only 10 genera compared to 32 genera during the Silurian

Period (Dickson 51). Shin Pond, Maine—where the L. C. Bates’s rugose coral came from—is known to preserve the best coral specimens (Dickson 288). The area is home to an unnamed conglomerate unit that contains a few scattered rugose corals among Early Silurian rocks

(Neuman 16). The lack of shallow waters during the Ordovician and the number of rugose corals contained within the Silurian rocks of Shin Pond could suggest that the Budden’s rugose coral is of Silurian age. Yet, it is harder to speculate about the fossil’s geologic formation. Robert B.

Neuman (14) claims that in prior reports completed on the Shin Pond quadrangle, most of the bedrock was grouped into formations that are outside the boundaries of the area. Furthermore, each report may have used different names to categorize similar rocks in different combinations

(Neuman). For example, the area designated “Shin Pond area (2)” has seven alternate names, each an unnamed formation composed of different rock types (Dickson 418). If the Budden

Collection’s rugose coral was recovered from one of the examined units inside the Shin Pond quadrangle, then making a specific identification of its geologic formation seems improbable— especially since the rocks of Shin Pond have not proved nameable. 10

Each fossil in the Budden Collection gives visitors of the L.C. Bates Museum a snapshot of geological Maine’s past. However, some of those snapshots can be blurry as a result of uncertainties and unidentified data for some of the specimens. In an attempt to investigate these unknowns, this paper challenges and builds on information about the Budden fossils by using previous literature and research published by geologists and paleontologists to speculate and ask questions. While geologists continue to work with Maine’s fossil record and study Maine’s bedrock, native fossil specimens at the L.C. Bates Museum can give visitors a glimpse into

Maine’s geological past and allow them to stimulate questions of their own about the known— and the unknown.

Sources Cited

Boucot, Arthur J. “Early Moose Paleozoic Brachiopods of the River Synclinorium, Maine.” Geological Survey Professional Paper 784 (1973): 1–81.

Boucot, Arthur J. “Stratigraphy of the Moose River Synclinorium, Maine.” Geological Survey Bulletin 1111 (1961):153–58.

Churchill-Dickson, Lisa. Maine’s Fossil Record: The Paleozoic. Augusta, ME: Maine Geological Survey, 2007.

Deborah Staber, email message to author, 14 April 2020.

“Dinosaurs Were Likely in Maine, but Evidence Is Nonexistent Thanks to Glaciers.” Lewiston Sun Journal (7 June 7 2015). https://www.sunjournal.com/2015/06/07/dinosaurs-likely-maine- evidence-nonexistent-thanks-glaciers/ [accessed 4 March 2020]

“Fossils Preserved in Maine Bedrock.” Maine Geological Survey (8 January 2008). https://www.maine.gov/dacf/mgs/explore/fossils/bedrock/fossil-bdrk.htm [accessed 4 March 2020] 11

Heath, E.W. “Stratigraphy and Structure of the Roach River Syncline, Piscataquis County, Maine.” Master’s Thesis, Massachusetts Institute of Technology, 1959.

Kite, J. Steven, and Thomas W. Kammer. “Occurrence of the Crinoid Rhodocrinites Nortoni (Goldring) from the Lower Devonian Seboomook Formation in the Telos Lake Area, North- Central Maine.” Studies in Maine Geology 1 (1988): 101–108.

Marvinney, Robert G. “Bedrock Geologic History of Maine.” Maine Geological Survey (24 September 2012). https://www.maine.gov/dacf/mgs/explore/bedrock/facts/geol-hist.htm. [accessed 4 March 2020]

Neuman, Robert B. “Bedrock Geology of the Shin Pond and Stacyville Quadrangles Penobscot County, Maine.” Geological Survey Professional Paper 524 (1967): 1–7.