Goldsboro Ridge OSL Dating Proposal
Abstract
The Carolina bays of the eastern coastal plain of the USA have been investigated for over 80 years, beginning in earnest when an aerial photographic survey of Myrtle Beach, SC revealed their enigmatic oval shapes and persistent alignments. The first 40 years of research produced a plethora of interesting and often amusing gradualist theory and catastrophic theories for the geomorphology of the bays, with the catastrophic solutions losing favor due to difficulties in many areas. Among the challenges for the previously-considered catastrophic hypothesis include: the lack of an obvious classic impact crater in North America; the implausibility that impacts directly excavated the bays, given their shallow depth; the existence of antecedent landforms surviving beneath them; the lack of correlation between the sand in the bay rims and the strata lying below the bays; the lack of deformational stratigraphy in the strata of the rim sand as well as in the underlying strata; and perhaps most damaging, the failure to identify a unique depositional date for bay landforms across their geographic extent when results of numerous carbon isotope and OSL dating experiments by workers are considered. Here, the author posits that the dates identified thus far were not executed using a robust dating methodology specifically addressing the structural bay rim sand, and that those results may represent only a minimum age for re-worked overlying surficial sands and adjacent sand dunes associated with the bays. This paper is submitted to address this shortcoming by proposing that an extensive OSL dating regimen be executed along a transect of the Goldsboro Ridge in North Carolina, with a goal of identifying the depositional age of the entire structure and its embedded Carolina bays. Justification for this approach is provided herein, and the reader is invited to consider participating in the experiment at any level they deem appropriate to their interests and skills.Introduction
My name is Michael Davias. Although I am not an accredited geologist, I am a participating member of the Geological Society of America (GSA), having presented the concepts discussed herein at numerous GSA meetings (LINK). My professional background is in the computer sciences, and I have made a relatively successful career for myself providing technical pre and post-sales support at several hardware companies. In these roles, I help assure the equipment is sold into the correct environments, and diligently insure that it remains sold by providing the customer with a satisfactory user experience.I pride myself in my problem solving skills, putting the optimal solution together with the guidance of my customers and my peers. Normal science - in the parlance of Thomas Kuhn - can also be viewed as puzzle solving. In both of these situations, progress towards a solution is encouraged by the knowledge that a solution is likely at hand with available tools applied to learned paradigms. Games, puzzles or sales campaigns that cannot be solved thusly are not much fun. In this context, I’d like to discuss a geological puzzle that seems to have defied solution despite the best efforts of several generations of respected professionals.
The Enigmatic Carolina bays
The Carolina bays of the eastern coastal plain of the USA have been investigated for over 80 years, beginning in earnest when an aerial photographic survey of Myrtle Beach, SC reveled their enigmatic oval shapes and persistent alignments. The first 40 years of research produced a plethora of interesting and often amusing gradualist and catastrophic theories for the geomorphology of roughly 50,000 “bays”, precipitating classical debates by respected geologists. (see Savage, 1982, for a comprehensive review). Meteorite impact craters, formed as the result of an exploding comet, were proposed early and often. Most problematic for a direct impact scenario, as well as for secondary impact craters formed by lofted masses of ejecta, is the very shallow depths of the bays when compared to their spatial sizes. Johnson identified numerous additional features that rule out catastrophic excavation of the bays, including: the survival of antecedent drainage channels across some bays; the obvious lack of deformation in the rim or the underlying strata; as well as that rim sands are usually not related to the underlying strata from a chemical perspective. A gradualist paradigm of “wind and wave” was introduced in the mid 1970’s, and today is considered by some to be a satisfactory solution. It is my contention that the true genesis of the Carolina bays cannot be solved using the “wind & wave” paradigm. Thus, it is not much fun, nor is it emotionally or intellectually profitable to identify and articulate a satisfying solution, allowing research and interest to languish over the past 40 years.Wind & Wave
The “wind & wave” concept had been raised early (Johnson, 1942), but was brought to the realm of consensus paradigm by the 1977 publication of Raymond Kaczorowski’s doctoral thesis on bay morphology. While the University of South Carolina published the thesis as one in a series of technical reports on coastal research, its findings have not appeared in any publicly accessible peer-reviewed journal. My first access to the thesis was through an accommodating geologist who supplied me with a copy he had “acquired in the day”.The process demonstrated in this thesis was fairly simple. It involved blowing a fan over a water-filled depression, alternatively in one direction then in the opposite direction on a 50% duty cycle. (Figure 1) The experiment was designed to replicate the action of high velocity katabatic winds blowing across depressions in the landscape during the glacial maximums, where cyclonic wind patters would be controlled by the existence of continental ice sheets immediately to the north. In this scenario, bays would have been created episodically, based on climate conditions during the Pleistocene era. The experiment produced a landform that vaguely represents a Carolina bay. Uncharacteristically, for a paradigm-setting experiment, no attempt has been made to date to replicate the process or validate the results. The lack of accessibility and distribution of the work may be responsible for the lack of articulation by others. Yet, workers occasionally reference the report, glossing over the anomalies and counterinstances it raises. One major shortcoming of the “wind & wave” theory is that it makes no attempt to address the genesis of the mandated pre-existing depressions, but merely attempts to explain how aligned ovoid planforms were crafted from them.
I maintain that the paradigm is false. Alternative mechanisms previously proposed, such as primary or secondary impact structures, similarly fail to meet Johnson’s challenge that any explanation must “fully account for all the facts observed”. Therefore, a novel theory must be invented. But who is going to provide that, and with what authority? Kuhn has a suggestion, from his perspective of scientific history:
“Almost always the men who achieve these fundamental inventions of a new paradigm have been either very young or very new to the field whose paradigm they change. And … are particularly likely to see that those rules no longer define a playable game and to conceive another set that can replace them.”
A Novel Theory
My novel theory might instructively be introduced by referencing Kuhn’s visual gestalt example: the marks on paper that were first seen as a bird are now seen as an antelope. In the present case, I’d like the reader to move from the instantiation of bays as gentle sand-rimmed depressions on an otherwise-nondescript landscape, to where an anomalous blanket of sand with occasional dimples is envisioned. Alternatively, if you will, turn a bay inside out so that we come to view the surrounding sand rim and pediments as the item of interest, and the bay simply as a void in that structure.My introduction to this inversion was an observation made by R.B. Daniels, et al, in the paper entitled “The Goldsboro Ridge – an Enigma”, published in 1970 in Southeastern Geology:
“The Goldsboro ridge is a unique feature on the Sunderland surface and requires special explanation whatever its origin. ...The Goldsboro sand overlies the Sunderland Formation conformably. The contact is always abrupt... Even the Carolina Bays do not disturb the underlying Sunderland materials.... The sand in the bay rim is not different from the Goldsboro sand. Therefore, these Carolina Bays are merely surface features associated with the formation of the ridge.“
To form the ridge (Figure 2), I speculate on a catastrophic deposition of sand, delivered to the coastal plain as distal ejecta from a remote cosmic impact. The uniform coarse grain size, unstratified, high purity quartz sand seen by Daniels in the Goldsboro Ridge is speculated to be the materialization of pulverized terrestrial and extraterrestrial siliciclastic materials. To generate the surface imperfections seen as Carolina bays, I speculate on a highly aqueous ejecta mixture whereby the foam’s “bubbles” are expressed in the surface as the ejecta matrix locks up while depositional energies subside. In this scenario, the bay’s crisply geometrical rims are attributable to the fluid dynamics of superheated steam inclusions in the ejecta matrix, while the aligned oval shapes are momentum artifacts of the ejecta arrival vectors. Viewed as a relatively thin (1- 10 meters) blanketing event, the ejecta matrix would have draped over antecedent terrain, allowing structural relief features such as scarps and drainage channels to map through. (Figure 3) The speculated ejecta distribution would have naturally extended beyond the coastal plain, but bay formation would have only occurred on flat surfaces of considerable extent, while in areas of higher relief, the blanket would have instead sloughed off down slope and into drainage channels.
Lost Impact
The absence of an identified cosmic impact crater of recent vintage on the North American continent is appropriately raised as problematic for any impact related genesis for the bays. To accommodate this, I invoke the existence of a multi-kilometer thick ice sheet at the impact site of a low-density cometary body. Furthermore, a highly oblique impact angle is proposed. Schultz and Stickle (2009) demonstrated that conditions such as these might produce minimal deformation in the underlying strata. Reworking of such a crater by the ongoing mechanical activity of the ice sheet would further reduce the impact evidence by distributing proximal ejecta across a wide area, where it would be interpreted as simple glacial till. Even given these proposed conditions, a catastrophic impact of the proposed magnitude is quite improbable. Should my hypothesis eventually move forward, it would require a new interpretation of cometary impact dynamics involving low density “fluffy, dirty snowballs”.Bay Alignment
The alignment of the bays’ major axis has been noted to vary systematically by latitude, which is problematic for a direct cosmic impact model, but would be expected in an ejecta distribution model, where the alignments would form a triangulation network back to the causal impact site. Attempts by others have failed to identify a triangulation focus, as they did not account for the dynamic effects of the Coriolis force, which would steer the ejecta as it transited over the rotating sphere of the Earth. Carolina bay landforms seen north of Virginia have historically been considered to display chaotic alignments, but previous work by the author (2012a) has successfully correlated them to the primary set using LiDAR-derived high-resolution digital elevation maps. Using the alignments documented in a comprehensive survey of 30,000 Carolina bay landforms, the author (2012b) has proposed a triangulation network that identifies a focus over the Saginaw Bay area of Michigan.Dating the bays
A necessary constraint implied in a catastrophic genesis for the Goldsboro Ridge is that a dating exercise must yield a unique age for the entire structure. By extension, that same date should be evidenced deep within all Carolina bay structures. The failure thus far to identify a unique date has been problematic for any catastrophic theory, and is used to defend a gradualist genesis. Without exception, the sands in question have failed to yield a date based on fossil evidence, as they are entirely unfossilifirous. Daniels’ granted a marine geomorphology to his Goldsboro Ridge deposit, but rightly mentioned in passing that the lack of fossil evidence was problematic for that solution.Carbon dating of organic remains within the bowls of Carolina bays typically report ages beyond the method’s technological limit of 45,000 years. A database of ~50 OSL dates from bays and adjacent sand dunes has show them to have been deposited or reworked at ages from the Holocene back to over 120,000 years ago. I interpret all dates documented thus far to be minimum age constraints.
David R. Soller, in his 1988 US Geological Survey Professional Paper on the history of the Cape Fear River Valley, made a pertinent observation. He describes how the eastward flowing Cape Fear River has been incising its southwest channel wall episodically for over 2 million years, migrating laterally in that direction as its bed is titled by the pervasive uplift of the adjacent Cape Fear Arch. This process has resulted in a series of ever-younger terraces existing at incrementally lower elevations as the terrain is traversed from the backbone of the Arch towards the current Holocene channel and flood plain. Immediately above the current-era Cape Fear River flood plain is the Wando Terrace, dated by fossil and OSL dating to have been created during the Sangamonian interstitial, hence well prior to the last Glacial Maximum of the Wisconsinan Glaciation. Dates of 30,000 years ago to 100,000 years ago are given for this terrace’s sediments.
Moving further upslope towards the Arch, Soller documents the terrace of the Socastee Formation, created during the interstitial preceding the Illinoian Glaciation. This is dated as being created while the Cape Fear River occupied this surface 200,000 to 300,000 years ago. (Figure 4 & Figure 5)
Considering dates for Carolina Bay formation, Soller makes the following statement of fact:
“Data gathered for this study provide a unique opportunity to indirectly date the formation of the Carolina bays and dunes. If it is assumed that all Carolina bays were formed by a single, unique climatic event, then this event must have occurred after deposition of the Socastee Formation and before deposition of the Wando Formation, as Carolina bays are prominent on the Socastee terrace but absent from the Wando. Since these terraces are correlated with isotopically age dated formations, the date of Carolina bay formation falls somewhere between roughly 100 and 200 ka, roughly equivalent to the Illinoian glaciation.”
When considering an extensive ice sheet over North America during the posited cosmic impact, the event would be constrained to the Illinoian Maximum, between 135,000 and 150,000 years ago. Supporting this interpretation, the entire Socastee terrace is covered with impressively defined Carolina bays, right up to the abrupt scarp to the Wando terrace. Hence, the event would have been coeval with the position of the Cape Fear River when it deeply incised the terrain as a response to the significant lowering of the Atlantic during the Penultimate Glacial maximum of the Illinoian.Falsification of Wind & Wave
The surface of the Wando Formation terraces, both along the Cape Fear River as well as along the Pee Dee River to the south and the Tar River to the north, is quite complex, with braided channels and depressions in a surface of unconsolidated sand. The Wando’s surface should be considered an excellent candidate for the production of “wind & wave” generated Carolina bays. Indeed, it is surrounded by significant quantities of bays on adjacent older surfaces, as evidenced in high-resolution elevation maps derived from LiDAR ranging systems. The Wando terraces were exposed to at least 130,000 years of weathering activity during which at least one glacial maximum was available to provide the continental ice sheet katabatic winds believed to episodically generate Carolina bays.The conspicuous absence of Carolina bay landforms on the Wando terraces - either incipient, well formed, or relic – is problematic for the “wind & wave” paradigm, and could be a persuasive argument against its application as the primary bay formation mechanism. If the “wind & wave” theory fails to deliver a reasonable, repeatable and verifiable mechanism for the creation of the robust Carolina bay landforms, perhaps alternative mechanisms should be investigated, including those of catastrophic origin such as the one discussed here.
Goldsboro Ridge Dating Proposal
I propose that that a rigorous OSL dating regimen be executed within the Goldsboro Ridge, taking at least 20 sand samples from the horizontal and vertical extent of a ridge transect. An opportunity exists during the summer of 2012, as a new exposure across the ridge will likely be opened during the ongoing US Route 70 Goldsboro Bypass construction project. To facilitate the effort, I will be providing at least $10,000 in funding. This synopsis is being provided to individuals who may be interested in supporting the OSL dating process, with a goal of documenting the actual depositional age of the ridge. The falsification of the impact-ejecta blanket theory would be achieved if the sand comprising the Goldsboro Ridge did not yield a consistent, unique depositional age within the resolution constraints of the technology.An elevation profile of the RT 70 ridge cross is shown in Figure 6. A Google Earth LKMZ file is available to inspect the proposed Rt 70 Right-of-way in the context of the LiDAR map of the area: Rt70_Bypass.kmz
Michael Davias, 6/7/2012
References
Daniels, R.B., Gamble, E.E., and Wheeler, W.H., 1971a, The Goldsboro Ridge, an Enigma: Southeastern Geology, v. 12, p. 151-158.Johnson, D. W., 1942. The Origin of the Carolina Bays. New York: Columbia University Press.
Kaczorowski, R. T., 1977, The Carolina Bays: a Comparison with Modern Oriented Lakes Technical Report no. 13-CRD, Coastal research Division, Department of Geology, University of South Carolina, Columbia, South Carolina. 124 pp.
Kuhn, Thomas (1962, 1970, 2012). The Structure of Scientific Revolutions. The University of Chicago Press. pp. 24–25. ISBN 978-1-4432-5544-8.
Soller, D. R. (1988). Geology and Tectonic History of the Lower Cape Fear River Valley, Southeastern North Carolina, U.S. Geological Survey Professional Paper 1466-A, pp. l-60.
Schultz, P. H.; Stickle, A. M., 2009, Lost Impacts, American Geophysical Union, Fall Meeting , abstract #PP33B-04
The North Carolina Department of Transportation, R-2554BB&C - US 70 (Goldsboro Bypass ) Project Design-Build Documentation,
LINK:http://www.ncdot.gov/doh/preconstruct/altern/design_build/R2554bbc/R2554bbc.html