Video
Understanding Dune Prehistory Along Southern Lake Michigan
Transcript
Karen Mudar: Dawn, you're going to have to introduce Gosia, because I'm not familiar with her, but I can introduce Dawn Bringelson who works at Midwest Archeological Center. She and her colleague are going to talk to us today about understanding dune prehistory along southern Lake Michigan, a topic I'm very interested in because I grew up Michigan. So Dawn, thanks very much for speaking with us today.
Dawn Bringelson: Thanks for hosting us, Karen. It is nice after you spend this much time preparing something for a conference to have a chance to actually let people listen to it. Sometimes you're standing at your post and you're wondering if anyone else is going to come by. I just wanted to say, when I put my abstract in for SAAs last year, I just put it in for myself, so I have to apologize. By the time the poster time came around, it made a lot of sense to have Gosia Mahoney, who works for the park archeology program here at the center as well, and Paul Hanson, who works at the school's natural resources at UNL, and runs the OSL lab there.
We'll talk a little bit more about OSL a little bit in the talk. I just wanted to say that. Gosia is in this room with me and will be able to answer questions. She's also going to be managing the audio-visual, or just the visual system. I will be the audio system. I will start now. Indiana Dunes National Lakeshore contains fifteen thousand acres of the last remaining intact dunelands within the highly modified landscape between Chicago, Illinois, and Michigan City, Indiana. This map shows park units in light red. We're going to focus today on the two units along the shoreline, which we will refer to as the East and the West units.
I have a note in here saying to note locations of Gary, Michigan City is up on the east side of the park. The Port of Indiana is in the middle between the two units. Then there's a series of in-holding neighborhoods. There's a state park and as you can see, there's lots of gaps within the boundary of the National Lakeshore. Indiana Dunes is characterized by sets of dune ridges and inter-dunal wetlands situated parallel to the Lake Michigan shoreline. These land forms have developed since the end of the Pleistocene with the recession of glacial Lake Chicago, and a series of lake level shifts throughout the Holocene. We have the lake border moraine, which held in Late Pleistocene lake waters and that dates to about 13.5 thousand years ago. Glenwood Beach Ridge dates to about 13,000 years ago. Can you see the little red dot moving around there?
Karen Mudar: I can't see it. Can other people see it? You have to hold it down. You have to left-click and then hold it down.
Dawn Bringelson: Oh, left-click and hold it down. Now can you see it?
Karen Mudar: No.
Dawn Bringelson: We'll work on that, but in the meantime, hopefully you can see the text on the screen. The Glenwood Beach Ridge dates about 13,000. The Calumet Beach Ridge, which is just north of that ... There, now do you see it?
Karen Mudar: Yes, thank you.
Dawn Bringelson: Calumet Beach Ridge was formed between 11-12,000. After this, lake levels dropped and the shoreline of Lake Michigan moved north significantly, so this particular area was inland for about 4,000 years. The Tolleston Dune Ridge, as you see further north there, near the Lake shore, didn't really begin to form until the mid-Holocene. I also want to note that the Glenwood and Calumet Dunes are linear beach ridges while the Tolleston and the recent dunes, closer to the lakeshore are more complex and broken land forms, so they form parabolic dunes, almost perpendicular to the shore line. The ridges set in close proximity to the lake provide an environment with a rich diversity of natural resources.
Early twentieth century scientists and naturalists competed with industrial developers calling for raw materials and a deep-water port. A compromise was reached in 1966 with the establishment of the national lakeshore, along with a zone set aside for industrial development. This last photo is just taken from the east end of the park towards the center part. You can see the deep-water port, the Port of Indiana, there in the background. We can look at the National Park Service archeology and Indiana dunes along with a continuum of intensity ranging from incidental discovery by the public and park staff to full-blown data recovery projects.
It's not surprising that the majority of what we've learned about prehistory in the lakeshore comes from projects that incorporate screening. Here, we have examples of site identification projects. At the top, we have a picture from a reservation of occupancy and use project where you have just a really small-scale shovel test inventory around a house lot, just to identify any archeological materials, usually associated with prehistory in the area of potential effect there. On the bottom is an archeological identification project funded by Cultural Resources, or what we used to call state funding sources. Examples of site evaluation and data recovery, here we have Tolleston Dunes Creek, along the Dunes Creek Corridor at the west end of the East unit, prior to the construction of the East unit campground further east. Those, of course, are going to be providing more data but in fewer project locations.
All of this work benefits from collaboration between MWAC and the park. Indiana Dunes is exceptional in the number of park staff across programs that participate in field work with the center. This is a pattern established from thirty years ago with the development of the Paraprofessional Archeology Program. The current chief of maintenance and of resources at Indiana Dunes are among the longest standing alumni of this program and have consistently supported MWAC research and management at the park. The combination of large- and small-scale inventory, testing, and data recovery have documented some 8,000 years of occupation of the Dunes, spanning the early archaic to historic periods. Artefact scatters mainly debitage and fire cracked rock make up most of the assemblages of the approximately 200 assemblages of archeological sites documented to date.
Chronologically, diagnostic items such as these are rare and the discovery is largely limited to the higher intensity investigation that I just talked about. Shovel test sampling, while the best way currently to identify archeology deposits within dune settings, is limited to common artifact classes and rarely provides much in the way of chronological resolution. Better resolution of occupation timing is critical to building our view of prehistory. Where within the lake shore people did live is also fundamental to understanding prehistory here. Site density is high along the linear Glenwood and Calumet dune ridges of the East Unit.
Initial views suggest little use of the Tolleston Dunes overall. This impression may be driven by spotty sampling in the Tolleston system, which is broken up by in-holdings across both units. A number of sites identified on the Tolleston is outnumbered by those on the older dune ridges just south of the Great Marsh, which I neglected to mention when we were looking at the map, but there's the Great Marsh there between the Tolleston and the Calumet dunes. However, it does not appear that site density on the Tolleston is actually lower, so comparing sites found per acre during systematic survey reveals the largest difference in site density is found between the East and West Unit survey polygon.
Is this difference explained by human behavior in prehistory? The distribution of sites south along the Calumet suggest this land once served as a regional transit route around the southern end of the lake. It is possible that the environment was in the current west unit was interspersed with swampy wetlands, and was not as easily traversed as were the beach ridge dunes to the south. However, historical geography does not necessarily support this explanation. This map detects trail systems established before 1830 and is documented in the historic record. Note the trail running through the West unit Tolleston actually passes near two identified sites. Given the assumption that these early historic transit routes were continuous from prior periods, this does not support a behavioral explanation for the low density of sites in the West Unit.
Land formation must also be considered. Given that the Tolleston was a sand spit until the mid-Holocene, a narrower range of pre-contact occupation is possible here. These figures are from Jay Sturtevant’s Dunes Creek report and it sort of illustrates the formation of the Tolleston system. When the lake levels rose again, the Tolleston was really a sand spit and the wetlands that are currently there were actually a lagoon that formed behind that spit. As the sands were reworked by wind-driven forces, the parabolic dunes formed and continue to form today. However, the parabolic Tolleston dunes in the West Unit have recently been dated via optically stimulated luminescence to about 3500 years ago. So, this would allow time for Mid and Late Woodland occupation time periods, which are much better represented in the East Units than they are in the West.
Formation processes in coastal dunes are demonstrated to play a large role in the preservation and discoverability of sites. Factors such as overall Lake Michigan water levels, coastal uplift and subsidence, and wind patterns all play into the history of dune formation and periodic reworking. MWAC is in the midst of a project aimed at improving understanding of pre-contact use of land forms across the park, especially in areas of the park for which the pre-contact record is still poorly known. The West Unit is one such area. We are using multiple methods and collaborative partnerships to investigate this. Project planning, for the current project, included development of an archeological GIS, incorporating information on previous survey areas, known site locations, and environmental variables.
The resulting model identified untested areas with higher probability to contain archeology and was used to collect areas for shovel test inventory. Shovel test sampling focused on high likelihood areas in Year 1 or 2012, and refocused on both low and high probability zones in Year 2. Sampling units span elevation differences across individual dunes and included consideration of previous wetlands locations through the addition of a hydric soil layer to the GIS. Shovel test inventory has reaffirmed lower site density in the Tolleston Dunes of the Lake shore's west unit. MWAC is now focusing on formation processes. Other research along Lake Michigan has demonstrated that dune-building processes have disturbed and/or have deeply buried archeological sites.
This is daunting, but not damning to archeology in the dunes. Because of its westernmost location along Lake Michigan, timing and severity of dune activation and reformation may have impacted archeology differently than dunes. More subtle differences in shoreline location may also relate to differential impacts to archeology between the East and West Unit Tolleston dunes. This slide shows evidence of reactivation and stabilization processes within a short time span. The shovel test was excavated on the top ridge of a parabolic dune in the West Unit. The charcoal layer that you can see here is associated with a prescribed burn that only took place a couple years ago. Obviously, these things can happen pretty quickly.
If sites are preserved, are they within reach of conventional archeological methods? A typical shovel test in Indiana Dunes is about 100 centimeters deep. Negative results may indicate a lack of prehistoric activity. They may indicate that archeological deposits are no longer preserved. They may also indicate that these deposits are out of reach of these field methods. We need to pare down these options, starting with our field method. We are using OSL dating to fine-tune our understanding of near surface sediment ages and the effectiveness of shovel testing as a method to access archeological deposits in these particular dune settings.
Samples shown here were collected from shovel tests of a parabolic dune in the West Unit. Sample 1, left, was collected from beneath the base of a hydric soil located near the center of the dune basin. Sample two, at right, was collected from the toe of the slopes from 50 meters north. Results provide hope for shovel test inventory in the west unit. Dune basin sediments date to about 3800 years ago. Toe slope sediments date to about 1200 years ago. Even dates from the shallow toe slope samples suggest shovel testing can at least sample the late prehistoric period. We anticipate two more years at Indiana Dunes. This will include additional work to better understand near-surface sediment ages in the West Unit.
2014 field work focused on analyzing parabolic dune formation with OSL samples collected to test geologic modeling of inter-dune sediment ages. We are expanding collaboration with geologists and archeologists from Indiana University Northwest, Indiana Geological Survey, and the University of Nebraska. Further work at MWAC will benefit from the development of geology thesis research with a focus on expanding geo archeological work on deeper dune sediments. This will evaluate the relationship between dune processes, site burial, and preservation. This will give the park more information about the nature of their archeological resources, especially in the West Unit. It will be useful for them to know, not only will they be impacting archeology resources, or can they access archeological resources with a shovel test, but perhaps they will also get some information about archeological resources that are more deeply buried beyond our conventional reach.
It will also help us improve field methods for site identification in dune settings and it will ultimately improve our knowledge of prehistoric land use of lake shore dune lands. I want to acknowledge the contributions of multiple researchers and managers in the development of this project, including Jay Sturdevant, who is a long time archeological contact for Indiana Dunes at MWAC. Todd Thompson and Bill Monahan of the Geological Survey, Erin Ardelan at Indiana University, Erick Inn and Bob Dom, who are managers I mentioned earlier at Indian Dunes and Amanda Renner of our office, who has been working us on the GIS, and also the many staff and volunteers at both MWAC and Indiana Dunes who have contributed to the field work over the years. That's it. Does anyone have any questions?
Karen Mudar: Does anyone have any questions for Dawn? I have a question.
Dawn Bringelson: Okay, thank you.
Karen Mudar: You had mentioned in the body of your talk that one of the factors that affected dune formation was subsidence. What kind of subsidence?
Dawn Bringelson: Subsidence of, like post-glacial subsidence, as the land form drops, that affects lake levels and the lake levels affect the beach ridges and how those are formed.
Karen Mudar: Wow, okay. I was thinking about glacial rebound, but this sounds like it's more recent than that.
Dawn Bringelson: Yes, it's linked processes. Gosia, do you have anything to add? She's over here motioning. She's talking about a hinge line.
Gosia Mahoney: It goes across in the middle of Michigan and one side subsides and the other one is upwards.
Dawn Bringelson: Does that make sense? It's both. In the southern part it's a little different from the northern part.
Karen Mudar: What is the ages of most of the sites then? They must be skewed toward more recent sites.
Dawn Bringelson: Most of our pre-contact sites are undated. That sets part of the challenges. When we have the more intensive investigations, the square holes tend to get more of the C-14 dateable material, so using OSL is really helping us to better understand ... It gives us the potential to understand a wider range of our pre-contact sites, because most of them are lithic scatters. We don't have a great handle on site structure, and locations of features until you start looking in a more intensive way. Jay did a lot of work along the Dunes Creek Corridor, and really did fine-tune some stuff there, so Jay ... I don't know, he's in the other room, so maybe he could chime in on some dates from Dunes Creek, if he's still in there.
Karen Mudar: Jay, are you there? I guess he's not.
Dawn Bringelson: He's not there. There's a good span to it, and I think at East Unit campground, we did have materials that were late prehistoric, and then also ... Now that I'm thinking about it, Jay has found some of those points that we showed, there's some Early Archaic occupations that show up along the Dunes Creek Corridor. It's a really wide range.
Karen Mudar: It looks like they're not another example of people in transit, or are they people who are coming exploit specific resources?
Dawn Bringelson: There's different models, but preservation in the dunes is not as good as it might be, like around the Kankakee south, and east, and west of the dunes, around the glacial areas or outside of the lake shore. It seems like there's a different kind of record there. We're trying to figure out, why aren't we getting these ... It's contemporaneous with one of these Upper Mississippian you're getting in that part of the world, but we're not seeing those kinds of deposits in the lake shore, so perhaps it is just a seasonal exploitation, or occupation strategy, but at the same time, it could be this preservation or varial, some of these dune issues.
We're just trying to ... Right now, to rule out formation processes, to get a better handle on behaviors.
Karen Mudar: You'll get really interesting results when you're able to sort that all out.
Dawn Bringelson: Let's hope.
Karen Mudar: Thank you so much. Does anybody have questions or comments about Dawn's presentation?
Description
Dawn Bringelson, 10/2/2014, ArcheoThursday
Duration
19 minutes, 19 seconds
Credit
NPS
Date Created
10/02/2014
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