This is the first in a projected series of posts in which I try to make sense of a newly acquired fossil collection. The collection is a mess, but trying to bring some order to it seems (at this stage) to be a worthwhile and interesting task. This initial post explores the likely geographic and geologic source of the bulk of these fossils. Later ones will describe and discuss some of the specimens.
Early on, I fell into a research abyss trying to answer the question: What's Plum Point? This is shorthand for a group of issues regarding the where, what, and why of Plum Point. Some of these I deal with better than others. Though this present post does have a very real fossil connection (something explored more directly in subsequent posts), it also reflects how an obsession with cartography that I didn't know I had led to hours exploring the name “Plum Point” or is that “Plumb Point” or even "Plumpoint?"
A fossil collection I recently purchased on the web has given me a glimpse of the bleak future for my own fossil holdings. The original collector (not the seller who acquired it at an estate sale) apparently wasn’t enamored of labels and didn’t invest much time in identifying the specimens. Here is one of the several containers in which the material came to me.
To be fair, these criticisms may not be entirely valid. I suspect that what I have in my possession is the remnant of a larger collection. Indeed, these fossils may be those that were assigned to the triage category of “boring and nothing special.” Supporting that conclusion is the complete absence of shark teeth (certainly present in the geologic formation feeding this collection).
Despite having taken to heart with my own collection the dictum to label, I suspect that many of the challenges this new collection poses will be confronted when mine is dispersed (that is, if it’s not simply tossed in a dumpster by my spouse or my kids). For starters, my labels are keyed to a master list of locations, so if that list is separated from the fossils, all bets are off. Further, outside of the most distinctive fossils, my attempts at serious identification of the fossils I’ve collected have been relatively few and far between. Finally, I know that if someone with paleontological expertise were to sort through my holdings, the biggest category created would be undoubtedly “boring and nothing special.”
This then begs the question, why am I planning on dedicating several posts in this blog to this newly acquired collection? Perhaps it’s because the challenge to make some sense of what I have at hand is irresistible, clearly requiring some sustained research. That many of the fossils are cetacean in origin and that some of the bony fragments appear, at this early stage of my exploration, to be from turtles increase the allure. Nevertheless, my commitment to these fossils is probably best explained by the evidence that a good portion of them were collected at Plum Point, Maryland. This place name evokes warm, though admittedly vague, early childhood memories. My grandfather’s brother and his wife owned property at Plum Point on the western shore of the Chesapeake Bay, and, when I was very young, my family would visit for beach outings. My older sister remembers a long hike down to a very narrow beach. Undoubtedly there were fossils to be found along the shore, but I don’t remember looking for them.
This initial post is focused on setting the context for future narratives about some of what makes up the collection. My first major struggle with these fossils was determining what the collector meant by the label on one box which read "Plum Point" and a couple of slips of paper (nestled with some of the specimens) on which was written “Plum Point, Md,” with dates in the early 1970s.
It’s not quite as obvious as I initially believed. In fact, the United States Geological Survey’s Geographic Names Information System informs me that, of the 21 geographic features in the United States named “Plum Point,” fully 5 of them are located in Maryland. Of these Maryland sites, four are capes (i.e., a high land sticking out into a body of water) and one is an unincorporated populated place. The red pins in the map below locate the four capes. I’ve circled the Calvert County, Maryland, red pin because it’s actually two overlapping pins: one for a cape and one for an unincorporated populated place.
(A bit of advice for me going forward: make sure that any place name used in my fossil labels is unambiguous. Some sources on how to collect fossils advocate for the use of precise location data such as coordinates from a GPS, something that no longer seems like overkill.)
That said, despite this number of potential candidates, I’m sure the location referenced in these meager labels is at or near the Plum Point in Calvert County (conveniently circled in the map above). This is the one associated with my family. That it yielded the fossils in this collection stands to reason because this cape is intimately linked to the incredibly fossiliferous Calvert Cliffs (dating 18 to 8 million years ago). The stratigraphic composition of the Cliffs includes the Calvert, Choptank, and St. Marys Formations. A segment of the particularly fossil-rich Calvert Formation was named the Plum Point Member because that is “where the beds [of that member] are typically developed.” (George Burbank Shattuck, Miocene, Text, Maryland Geological Survey, 1904, p. lxxiv. Shattuck originally named this stratigraphic layer the Plum Point Marl.)
Shown below is the Plum Point (Calvert County) portion of the Maryland Geological Survey’s 1968 geologic map of Maryland as made available on the United States Geological Survey website. (A hint at place name problems I would have later is seen in this map section. Note that the name "Plum Point" appears to be associated with a location back from the water's edge, probably the unincorporated populated place.)
The pink colored bedrock formation seen in this map marks outcropping of the Plum Point Member of the Calvert Formation. My crude estimate is that this member is roughly 17 to slightly less than 14 million years old (estimate based on Figure 1.3 in The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA, edited by Stephen J. Godfrey, Smithsonian Contributions to Paleobiology, Number 100, 2018).
What’s striking about a view from the Bay toward the shoreline of Plum Point is that where the cape (barely) protrudes into the Bay is mostly sandy beach (Plum Point Creek flows into the Bay at this juncture) and the Calvert Cliffs are notably absent (eroded over the eons by the creek?). From a paleontological perspective, the area identified as Plum Point is wider than the most immediate area at the cape. The geological profile below of this area captures this phenomenon. This profile is modified from the diagram included in the Calvert Marine Museum’s Fossils of Calvert Cliffs (1995, 3rd edition). (That diagram, in turn, was modified from the one prepared by Peter R. Vogt for the Geological Society of America Centennial Field Guide – Northeastern Section (1987). It appears in the chapter by Vogt and Ralph Eshelman titled Maryland’s Cliffs of Calvert: A Fossiliferous Record of Mid-Miocene Inner Shelf and Coastal Environments.)
Given that the fossils in this collection are well worn, I assume they were captured primarily as “float” along the shoreline and not dug out of the cliffsides. Further, I strongly suspect that the collector worked along some narrow beach at the base of the cliffs, not in the stretch where the cliffs are absent. I have in mind an area like that pictured below in a 2019 photograph in the public domain from the U.S. Geological Survey which is labeled “Calvert Formation Near Plum Point, MD." It captures, I believe, work on a project studying foraminifera gathered from several sites along the Calvert Cliffs. One product of this effort appeared in the newsletter of the Calvert Marine Museum’s Fossil Club (Microfossils From Calvert Cliffs Give Us Clues to the Future Warmer Climate, The Ecphora, September, 2021).
Certainly, any effort to answer a question (to wit, where is Plum Point?) can only prompt still more questions. One that popped up is: why the name Plum Point?
According to geologist and paleontologist Ralph Eshelman, in the 1600s Plum Point featured a significant sand bar that swept to the southeast and then turned to the south. (Eshelman is truly a man of many, diverse talents. See, for example, Southern Maryland Matters and Mavens: Dr. Ralph Eshelman, by Sal Icaza, The Southern Maryland Chronicle, June 22, 2022.) In his draft history of Plum Point, Eshelman cites a source identified as "Briscoe 1954" for the explanation that the name derives from the presence on the sand bar of "plum trees" or perhaps "sand plums." (Pursuing his citation for this explanation has been, dare I say it, fruitless. Despite my proclivity to worry an issue to death, I don’t propose to tackle the question: is the fruit-link the impetus for all those other Plum Points in Maryland and elsewhere in the United States?) [After the initial posting, this paragraph was edited in part to include the reference to "sand plums."]
A map of Maryland and Virginia published in 1673 identifies the point as Plum Point and clearly shows the sand bar. The image below was cropped from the map by Augustine Herrman and Thomas Withinbrook, Virginia and Maryland as it is planted and inhabited this present year 1670, 1673. (Retrieved from the Library of Congress.)
In pursuit of Plum Point across the centuries, I spent a mostly enjoyable several hours exploring a wide variety of historical maps of Maryland at the David Rumsey Map Collection. It is a simply amazing resource that makes many thousands of maps available for online searching in great detail. My qualification of the enjoyable nature of this part of my research is due to what I found or, sometimes, didn't find, and has nothing to do with the site.
I documented in various maps how the spelling of the name of the Calvert County's Plum Point was inconsistent across the centuries. After the very early map shown above had it as "Plum Point," I came across several maps of the area from the 18th century which identified the site as "Plumb Point." Others in the same period continued with "Plum Point." Most of those from the first two-thirds of the 19th century that I examined identified the site as “Plumb Point.” Not until the latter portion of the 19th was the name of the point somewhat more likely to be spelled “Plum Point.” I expected to find that in the 20th century, the spelling became standardized at "Plum Point." Instead, I found maps distinguishing the physiographic feature (the cape) from the populated location, and introducing another variant into the mix. For instance, a 1924 Rand McNally map identified the cape as "Plum Point," and the population center as "Plumpoint." A 1927 map from the National Map Company also identified the populated site as "Plumpoint," without labelling the cape at all. At this juncture, I decided to cut my losses and not try to find out when in the 20th century the spelling actually became fixed at "Plum Point" for both the populated area and the cape.
Admittedly, during this process, I wondered if Eshelman (and Briscoe) might be wrong and there is in fact a definition of “plumb” applicable to the geographic location since that was where most maps in the first two-thirds of the 19th century appeared to settle. In other words, could I prove that this spelling ("Plumb Point") was intentional and not just a variant of “plum” in reference to the fruit? Some time with the Oxford English Dictionary showed me that I couldn't make that case. The spelling of the fruit’s name was quite variable through the 18th century. It included such variants as “plumme,” “plumbes,” and “plumbs.” (A source for this last spelling is Thomas Jefferson, who wrote in Notes on the State of Virginia (1787 edition, p. 64) that Virginia orchards produce: “apples, pears, cherries, quinces, peaches, nectarines, apricots, almonds, and plumbs.”) I imagine that when some cartographer first spelled the name of the point as “Plumb,” it was just carried forward in many subsequent maps. Not surprising given how flexible spelling was at the time.
Always a glutton for punishment, I also dug into question of whether the fluctuation in spelling affected the other Plum Points in Maryland. Though these other locations were unlikely to show up in historical maps of Maryland or the Chesapeake Bay, in the several instances when they did, their spelling varied in sync with how the Calvert County spelling changed. More support for Eshelman (and Briscoe).
My apologies, yes, I am often “a dog with a bone,” so I did more and poked around to see if the spelling fluidity affected any of the non-Maryland “Plum Points.” In this instance, I lost interest relatively quickly because, with one exception, the few locations I looked for did not appear at all in historical maps. That one exception reflected the Maryland experience: Plum Point on Centre Island in Oyster Bay, New York, appeared as “Plumb Point” in an 1863 map and as “Plum Point” in maps of 1873 and 1888.
The most salient conclusions reached in this post?
- The fossils associated with the Plum Point label in this collection were very likely collected somewhere on the shoreline at the foot of the Calvert Cliffs near the cape in Calvert County, Maryland.
- As a result, these fossils are likely to date from about the middle of the Miocene epoch.
- Naming a geographical feature “Plum Point” in the United States has not been a one-off.
- Calvert County’s Plum Point is possibly named for the fruit that once grew on a sand bar that is no longer there.
- Spelling of the fruit name in the colonial period and for awhile afterward was in flux.
- Studying maps at the David Rumsey website is a wonderful way to do research.
- Questions beget questions.
Posts
