Rock Art Dating Methods: Problems and Solutions - Arabian Rock Art Heritage
In archaeological terminology, there are two categories of dating methods: absolute lichenometry, micro-erosion and micro-stratification analysis of patina. Often there are multiple sites of varying ages nearby and the petroglyph itself may. Main · Videos; Patination in dating rock art. It's valuable in the way a man would measure aboard or he was promising to ravish his hopefulrealism. Vice all that. Introduction to dating cave paintings However, dating rock art has been a . Sweinfurth, in , was one of the first to use patination to date some engravings.
Then we may have something like the oldest histories in the world. But there are difficulties with each step in collecting this kind of evidence. When Was Rock Art Made? Petroglyphs are made by removing the outer dark surface of rocks, called rock varnish or patina, to reveal the lighter rock underneath. Stone is not directly datable in the time frame of human history. But patina takes a long time to form. It is created by bacteria living on the rock and attaching clay particles to the rock.
In the process they incorporate the element manganese, which gives a dark color. As soon as patina is removed, bacteria start to create patina again on the new surface. Roughly, we can say that darker petroglyphs are older, because they have been exposed longer to formation of patina.
But this works only roughly, because surfaces exposed in different directions and to different weather will form patina at different rates. Pictographs are made by painting on rock surfaces. If either pigments or binder contain carbon, they may possibly give a basis for radiocarbon dating. But this also has limits, because of organic contamination, and because we do not wish to destroy painted rock art to date it.
There are other chemical processes affecting rock surfaces which are being explored and which hold out promise for the future. Rock Art As Part of Archaeology Sometimes the production of images on a rock leaves a record in the ground just below that rock. Stones used for pecking petroglyphs, brushes used for applying paint, mortars used to grind pigments and small fireplaces used to change minerals into pigments, these and other objects can link rock art with more typical archaeological materials found in the ground.
In that same ground there may be charcoal from a hearth or other organic materials permitting radiocarbon dating. And there are other ways of treating rock art as simply one more kind of evidence in archaeology.
Here is more information. The relative darkness of petroglyphs on a single rock surface may give their relative dates. Which motifs tend to occur often together, and which never do? Who Made Rock Art? Sometimes this is because of where the rock art occurs, as at habitation sites of a particular culture. Sometimes it is because objects are pictured in the rock art which have been discovered in archaeological excavations, or which are known from ethnography the study of living cultures, often early records of contact between Europeans and peoples living in some area In certain very fortunate situations, we know who the people were who created rock art, we even know their names as individuals.
Such a ledger book may be signed. Or we may not know the individual who made particular rock art, but we may know that the individual belonged to a cultural group whose rock art consistently used those symbols in particular ways, similar to that in the ledger books. This demonstrates, conservatively, that the petroglyph tradition began before 11, YBP, probably before 12, YBP, and potentially in the 14, years range.
Comparison of these ages with evidence from other regions in the hemisphere demonstrates substantial artistic and stylistic variation in rock art by the Paleoindian period circa 10,—11, YBP. This suggests that, while art may have been part of the baggage of the first immigrants, regional cultural traditions had already been developed by the Terminal Pleistocene, if not earlier.
The result is evidence for the development of regional cultural diversity in the Americas by Paleoindian times. Introduction Few New World archaeological problems have received more attention than and experienced as much debate as the initial peopling of the Americas. Even with decades of research, basic questions like the earliest entry date and colonizing route remain elusive. Despite these uncertainties, the majority opinion currently seems to maintain that humans first arrived sometime prior to 13, years ago, though how much earlier is unknown e.
More confidently, there is a consensus that the initial immigrants where behaviorally modern, in the archaeological sense of these terms e. A key attribute of archaeological modernity is the ability to conceptualize and employ symbols, including the capacity to make and use art [ 4 ]. Although we still do not know when humans arrived in the Americas, we can assume that they were fully capable of producing art, and potentially had the proclivity to do so. But what and where is the evidence for the earliest American art, and what does it tell us about the peopling of the hemisphere?
This demonstrates that it is more common than generally recognized, includes both portable and landscape i. These studies are summarized below with the intent of providing a hemisphere-wide overview of early symbolic behavior. My point of departure in this discussion is a chronometric reanalysis of Great Basin petroglyphs rock engravingsdirected specifically at identifying the earliest art in far western North America.
This necessarily requires a discussion of recent advances in petroglyph dating techniques before turning to the larger issues at hand. Great Basin Rock Art Great Basin petroglyphs are well known due to influential early syntheses of this art [ 1112 ]. No accurate figure has been obtained for the number of Coso motifs, but credible estimates vary from hundreds of thousands to millions of individual engravings.
It is believed to be the largest rock art concentration in the Americas, and perhaps one of the biggest in the world. But simple and complex geometric designs are typical roughly one-third of the total and are frequently intermingled with the ostensibly identifiable images.
Mojave Desert, California, rock engravings are predominated by images of bighorn sheep, followed numerically by anthropomorphic figures and next by a variety of geometric forms. This example is from Sheep Canyon in the Coso Range. At other Great Basin sites, outside the Cosos, the same motif assemblage typically occurs, although geometric designs commonly predominate.
The Coso petroglyphs vary from the remainder of the Great Basin art not due to significant stylistic or known cultural differences but instead as a function of variations in the proportional motif emphases at individual sites and within smaller regions. Petroglyph Chronometrics Any discussion of potential early art requires a consideration of dating; in this case, rock art chronometrics and much of the early rock art chronometrics research was conducted in the Coso Range and Mojave Desert e.
By the mids, three independent rock varnish dating techniques had been developed and applied to petroglyphs: An unfortunate controversy developed concerning this last technique in the late s1; one result of which is the widespread but incorrect assumption among archaeologists that rock varnish dating as a whole is no longer viable [ 32 ].
Although AMS-WRO dating is in fact currently unusable [ 3334 ], the controversy strictly had no implications for the other techniques, and significant geomorphological research on them has occurred in the interim. In light of the varnish dating controversy and the uncertainties and misunderstandings that it generated, I discuss the current status of these two chronometric techniques before turning to the revised rock art chronology. Cation-Ratio Dating The CR technique was developed by Dorn and first applied to petroglyphs in the early s [ 24 — 2729 — 3135 — 38 ].
Though initially employed in the Americas, it was subsequently used in South America, Africa, Asia, and Australia discussed below.
It is based on cation exchange processes in the rock varnish that coats many petroglyphs in arid regions. These processes leach out mobile trace elements notably potassium and calciumthrough capillary action, more rapidly than less mobile trace elements particularly titanium; see [ 293039 — 42 ]. The rate of change can be calibrated regionally, using independently dated control surfaces, such as varnish-covered basalt flows. An electron microprobe is typically used to measure the chemical constituents of varnish samples, which are pin-head sized flakes that are removed from the engraved-out portion of a revarnished petroglyph.
The first CR petroglyph dating results were controversial in two ways. On the archaeological side, the initial research focused on presumed earliest motifs and unexpectedly obtained a handful of pre-Clovis aged results [ 26274344 ], that is, dates older than 11, years old, then assumed to be the start of the Clovis period.
When these dates were first reported, many North American archaeologists considered them an empirical impossibility, due to the then-prevailing consensus concerning the Clovis first peopling of the Americas2. The result was extreme skepticism, if not outright rejection, of the newly introduced technique, for straightforward reasons: Two decades later, archaeological opinion has reversed and now supports greater time depth for the initial colonization of the hemisphere.
This change in circumstance does not prove that the pre-Clovis CR ages were correct, but it negates the original archaeological argument against and attitude towards the technique. As is often the case with research on new topics, this resulted partly from simple confusions; first over techniques and analytical measurements used to assay the varnish sample chemistry e. Replication is often considered the gold standard of science, yet there are multiple potential reasons why a replicative test might fail, beyond the validity of a technique alone e.
Included in these is my own replication, fully independent of Dorn and his lab, in southern Africa [ 65 ]. In addition to multiple replications, the technique has also been successfully subjected to petroglyph dating blind tests [ 66 — 69 ]. Though I discuss the validity of CR dating in more detail below, it is worth noting here simply that it has analytical weaknesses, probably the most pronounced of which is that it is based on geochemical processes and these potentially can reverse over time.
Although the initial CR dates were experimental, their recent combination with VML dating below provides greater scientific confidence in the resulting assigned petroglyph ages. Varnish Microlamination Dating Perry and Adams [ 70 ] first observed continuous orange microlayers in thin sections of rock varnish, interbedded with black bands, representing manganese-poor and manganese-rich layers, respectively. Subsequent research has shown that these microlaminations occur over wide regions and correlate with major paleoenvironmental changes—alternating dry and wet periods [ 29 — 313771 — 76 ].
It is conceptually analogous to dendrochronology in that it involves the identification of regional microstratigraphic signatures similar to tree growth patterns caused by climate change, although it lacks the temporal resolution of tree-ring dating. The initial utility of VML dating in fact was hampered because it was restricted to a layering sequence for the Late-Terminal Pleistocene.
Micrographs showed the Pleistocene-Holocene boundary as a change in micromorphology, with botryoidal layers developing during the earlier wetter period and lamellate varnish during the drier Holocene.
The shift from botryoidal to lamellate micromorphology is currently understood as the change from the LU1 to LU2 paleoclimatic periods terminology from [ 6 — 8 ]; see Figure 2 and is set at about 12, yrs cal BP. Image courtesy of Liu. The microstratigraphic distinction proved to be more easily seen in thin section, and Dorn identified seven Pleistocene wet event dark layers that are rich in Mn and Ba, matched by six intervening less wet period light layers that are rich in Si and Al.
The sequence initially extended from 12, to about 60, cal yrs BP. The only visible microstratigraphic change whether seen with micrographs or thin sections in the archaeological time range then was the Pleistocene-Holocene boundary, thereby effectively precluding the use of the technique for most of the New World archaeological record.
Although originally developed by Dorn, Tanzhuo Liu improved and extended the technique subsequently, working at the Lamont-Doherty labs at Columbia University with Wallace Broecker. It resulted in improved temporal resolution of the Pleistocene sequence and the extension of the technique back to aboutcal yrs BP [ 75 ].
It also included a blind test matching VML results against cosmogenic dating [ 7778 ]. Liu more recently has defined the Holocene VML sequence for the Mojave Desert [ 5 — 10 ], making the technique fully applicable for archaeological purposes in this region.
The lengths of the intervals between wet events vary from to years, with an average of —roughly years. The resulting correlated VML ages are certainly not as precise as radiocarbon ages, but they are adequate for age assignment to the broad time periods comprising the regional cultural historical sequence. Importantly, VML dating has been independently replicated and applied to the archaeological record by different research teams working in the Sahara Desert [ 80 — 83 ], and Argentina [ 84 ].
Although regional microlamination sequences appear to vary and require local calibration, the Saharan, South American, and other international studies [ 8586 ] indicate that VML has the potential for widespread application in arid and semiarid environments. Over a decade of research also resulted in a Holocene VML calibration [ 57 — 10 ]making this approach widely applicable in archaeology. This calibration was developed for the Mojave Desert, thereby facilitating its application to the Coso Range and other eastern California petroglyph localities, and accommodating its use as an independent check on CR dating.
Rock Art Dating Methods: Problems and Solutions
In order to reevaluate the Great Basin petroglyph chronology, a series of chronometric analyses were conducted, some of which involved blind tests, with the assistance of Dorn and Liu, each working independently. These involved dating newly sampled petroglyphs and archived petroglyph varnish samples and thin sections, combined with previously obtained petroglyph ages from six rock art localities in the Mojave Desert: Sixty-seven petroglyphs and one natural control rock surface are included in the sample, representing independent chronometric assays3 Table 1 —one of the largest chronometric rock art data sets in the world.
These data were obtained and analyzed in the following fashion. Using the published Holocene calibration [ 5 — 10 ], Dorn chronologically interpreted and annotated images of each of these thin sections. These were submitted to Liu blindly: Liu prepared the thin sections and interpreted the results. This too was conducted as a blind test in the sense that the primary goal was to resample previously dated petroglyphs to confirm or reject their pre-existing calculated ages, as well as to sample additional engravings.
Liu was given no information on the name of the sites visited, the previous petroglyph ages, or their sample identifications in the literature. Two points need emphasis in order to understand the results. VML analyses involve the identification of the time period during which revarnishing began to develop.
As noted above, during the Holocene these periods average about years in length, but their spans range from to years. Liu reports his VML ages as single dates e. His use of this convention is intended to emphasize the fact that these are minimum-limiting ages, not specific calendrical determinations. There are two implications of this circumstance. This reporting convention, however, makes cumbersome the comparison of VML results to other chronometric ages in standard form using a comparison between calculated standard errors.
Nonetheless, the VML ages are adequate for the construction of a petroglyph chronology, and for a generalized independent evaluation of CR dating. The objective was to obtain confident temporal assignments. Note however that none of the VML readings were rejected as clearly in error by either analyst; instead in some cases Liu or Dorn felt that additional sampling and thin sections are required for full confidence in specific inferred minimum-limiting ages. Although I use these provisional VML ages below, they should be recognized as not yet independently verified by a second analyst.
Analytical Concordance The comparability of the results using the two dating techniques has implications at two levels: As noted above, the comparison of the results from these two techniques involves different mathematical conventions so that the standard criterion—whether the sets of ages overlap at one or two standard deviations—cannot be employed. That said, it is still apparent that the concordance between the two dating techniques is good, especially when both analysts agreed on the VML age assignments.
Fourteen of the 32 have CR ages that statistically overlap the minimum-limiting VML ages confirmed by both analysts at one standard deviation. Another barely misses that standard by years but matches it at two standard deviations. Although these two ages strictly are not statistically equivalent, they are both Early Archaic temporal assignments, falling within the same millennium. VML rock engraving thin sections. Dark bands of the subunits represent wet phases as follows: Images courtesy of Liu.
The immediate implication of these results is the following. CR dating is a usable even if imperfect chronometric technique. It clearly can provide a general sense of petroglyph temporal placement for a suite of samples, even though its accuracy on any specific single motif may potentially be in error.
- Rock art dating
- Journal of Archaeology
The comparison of the CR and VML ages also assists in the identification of incorrect chronometric ages—where the disparity between the two results is so great that one of the assays is clearly wrong. Two additional petroglyphs have ambiguous results, for various reasons.
These too can be eliminated from any further consideration of the petroglyph chronology in the western Great Basin. Revised Petroglyph Chronology Three kinds of chronometric evidence are available for revising the western Great Basin petroglyph chronology: Note that three of the four petroglyphs with VML ages alone involved multiple samples and thin sections.
In each case these were internally consistent. The most conservative interpretation, based solely on 16 concordant CR and VML ages verified by both analysts, indicates that petroglyph production began in the western Great Basin at least 11, years ago and that it continued into the last years. With the exception of two earlier dating motifs, discussed below, good though not quite as certain evidence suggests that the overall age range of the petroglyphs is 12, to yrs cal BP—from the Terminal Pleistocene to the protohistoric period.
Note that recent rock art production is independently supported by ethnographic accounts and historical subjects in the art; cf. These eleven petroglyphs provide strong support for Paleoindian or earlier rock art production in the region.
Understanding Rock Art
Motif R96ST13 warrants special mention Figure 4. As noted previously, a blind test identification of this motif, by a paleontologist specializing in Pleistocene Mojave Desert fauna, suggested that it is an extinct species of North American llama, thereby indicating that it should be early Holocene or earlier in age [ 183287 ].
An experimental AMS 14C age was obtained on a calcium oxalate layer interbedded in the rock varnish. It provides stratigraphic and chronological concordance with the minimum-limiting VML layer and age, and the CR results.
Although additional sampling is required to fully verify this age, four lines of evidence support the possibility that it represents a pre-Clovis aged petroglyph.
Engraving photo by Whitley; thin section image courtesy of Dorn.