Amber Taphonomy and Collecting Biases Author(S): Edward M

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Amber Taphonomy and Collecting Biases Author(s): Edward M. Pike Source: PALAIOS, Vol. 8, No. 5 (Oct., 1993), pp. 411-419 Published by: SEPM Society for Sedimentary Geology Stable URL: https://www.jstor.org/stable/3515016 Accessed: 11-10-2018 13:20 UTC

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This content downloaded from 129.240.204.123 on Thu, 11 Oct 2018 13:20:39 UTC All use subject to https://about.jstor.org/terms RESEARCHRESEARCH REPORTS REPORTS 411 411

Amber Taphonomy and Collecting Biases

EDWARD M. PIKE

Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N-1N4, Canada

PALAIOS, 1993, V. 8, p. 411-419 1982, 1988; Wood et al., 1988; Turnbull and Martill, 1988). Insect faunas are rarely preserved (although when insects Taphonomic processes affecting samples of amber inclu- are preserved, numbers of individuals are frequently very sions are outlined. Comparison of traditional collecting high). Consequently, development of hypotheses about methods dependent on human recognition of amber nod- terrestrial paleoenvironments and community composi- ules (hereafter called picking) with bulk sampling, tion and structure in terrestrial paleoecology has relied screening and salt water floatation indicate that signif- primarily on stratigraphy, paleogeography, and contribu- icant amounts of amber are overlooked by traditional tions made by paleopalynology (e.g., Batten, 1984; Tra- methods. Picking over-represents large nodules and un- verse, 1988), although inferences based on oxygen isotope der-represents small ones. This is significant because small ratios (Douglas and Woodruff, 1981; Shonfeld et al., 1991; nodules produce the highest number of inclusions per Dansgaard, 1981), and paleotemperature analyses inferred kilogram. Although small nodules have the lowest trap- from marine assemblages including foraminifera (Koll- ping efficiency, this liability is more than compensated man, 1979; Gerstel et al., 1986; Keller, 1983), have also for by their abundance and high proportion of external been applied to terrestrial ecosystems. Plant morphology flows. Bulk screened samples produce more inclusions per (Axelrod and Bailey, 1969; Wolfe, 1980) and wood analysis kilogram of amber with lower between-sample variation. (Creber and Chaloner, 1984; Taylor, 1990) have made sig- The proposed sampling method, if universally applied, nificant contributions to terrestrial paleoecology, and our would eliminate investigator bias in amber samples and understanding of the formation and interpretation of bone establish a baseline for standardizing quantification of beds is growing (Behrensmeyer, 1975, 1982, 1988; Beh- amber faunas. Bulk sampling and assessment of diversity rensmeyer and Hill, 1980; Dodson, 1971; Turnbull and per kilogram of amber allow more accurate estimation of Martill, 1988). total arthropod fauna through taxon/mass curves. Com- Most of these methods are subject to taphonomic error pleteness of sampling can be estimated through evalua- through transport (see Traverse, 1988, for palynological tion of standard errors of species abundance as mass of summaries; Scheihing and Pfefferkorn, 1984; Ferguson, amber increases. Consequently, community structure and 1985; Spicer and Wolfe, 1987, for plants; references above organization can be more accurately described and com- for vertebrates) or are indirect. Few of these data sets are pared with extant communities or other amber faunas, amenable to quantification of abundance, which leaves and changes in terrestrial arthropod diversity over time terrestrial paleocommunity structure and organization can be more accurately measured. largely inaccessible. Consequently, additional methods of testing paleoenvironmental and paleoecological recon- structions are useful, particularly if they can address abundance and species richness simultaneously. INTRODUCTION The abundance and exquisite condition of arthropods preserved in amber offer a unique data set for systematic Terrestrial communities are not conducive to preser- and paleoecological studies. While systematics of amber vation in situ due to the nature of the origin and deposition fossil inclusions has received considerable attention (Keil- of sediment loads and the structure of terrestrial organ- bach, 1982; about 300 publications are listed by Spahr isms, primarily plants, soil arthropods and nematodes, in- [1981] for Coleoptera alone), paleoecological applications sects, and vertebrates. Plants decompose rapidly or frag- have been largely ignored. Yet the transparency of amber ment (see Stewart, 1985, for a comprehensive review of suggests that abundance should be easy to quantify, mak- paleobotany and the problems of plant reconstruction), ing community structure and organization at least par- while soil fauna are relatively soft bodied and decompose tially accessible. with the exception of arthropod cuticle (Labandeira et al., Resins are known from Carboniferous sediments, and 1988; Shear et al., 1984). Terrestrial vertebrates are usually are still produced today (see Table 1). Resins known to few and far between, or are scavenged, fragmented, or contain insect inclusions range in age from about 120 Ma concentrated in bone beds (Dodson, 1971; Behrensmeyer, (Lebanese amber) to Recent (African and New Zealand

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TABLE 1-Age and location of known fossil resins. Modified from Langenheim (1969) with additional deposits referenced.

Carboniferous Tertiary (Eocene) Northumberland, England Princeton, British Columbia, Canada (**) Upper Mississippi Valley, U.S.A. Hukawang Valley, Burma Montana, U.S.A. Simi Valley, California, U.S.A. Cape Breton, Nova Scotia, Canada (Hills, pers. comm.) Malverne, Arkansas, U.S.A. Jurassic Fushun, China Bornholm Tertiary (Eocene/Oligocene)

Lower Cretaceous Seattle, Washington, U.S.A. Jezzine, Lebanon (Zur Strassen, 1973) Tertiary (Eocene/Oligocene, Miocene) Jordan (Bandel and Vavra, 1981) Baltic coast Israel (Nissenbaum, 1975) Tertiary (Eocene, Miocene) Lower Cretaceous (Albian) Rhineland, Germany Maryland, U.S.A. Tertiary (Oligocene) Upper Cretaceous (Cenomanian, Turonian, Coniacian) Argentina Magothy River, Maryland, U.S.A. Dominican Republic Martha's Vineyard, Massachusetts, U.S.A. Savoy Cliffwood, Bordentown, New Jersey, U.S.A. Saxony, Germany (Schumann, 1984) Kreischerville, New York, U.S.A. Tertiary (Oligocene, Miocene) Kuk River, Alaska, U.S.A. Chiapas, Mexico Upper Cretaceous, Campanian Tertiary (Miocene) Medicine Hat, Alberta, Canada (McAlpine and Martin, 1969) Dinosaur Provincial Park, Alberta, Canada (*) Para, Brazil Taber, Alberta, Canada (**) Carpathian Mountains, Rumania Central Sumatra Baja California, Mexico Upper Cretaceous, Maastrichtian Tertiary (Miocene, Pliocene) Grande Prairie, Alberta, Canada (*) Aukland Province, New Zealand Edmonton, Alberta, Canada (*) Tertiary (Pliocene) Upper Cretaceous Victoria, Australia Java St. Georges, Delaware, U.S.A. Kinkora, New Jersey, U.S.A. Luzon, Philippines Roebling, New Jersey, U.S.A. Tertiary Harrisonville and Pemberton, New Jersey, U.S.A. Medellin and Giron, Columbia Cedar Lake, Manitoba, Canada (?) Magdalena, Chile Cretaceous (undetermined) Guayaquil, Ecuador Hardin County, Tennessee, U.S.A. Northern Sicily, Italy Black Hills, South Dakota, U.S.A. S.E. Borneo, Indonesia Canon Diablo, Arizona, U.S.A. Hokkaido, Inotani, Japan Terlingua Creek, Texas, U.S.A. Sakhalin, Russia Haiti Ellsworth County, Kansas, U.S.A. Peace River, British Columbia, Canada Tertiary (Pleistocene) Hare Island, Greenland Tel-Aviv, Israel Vienna, Austria Hungary Tertiary/Recent Switzerland N.E. Angola Bahia, Brazil Tanzania (Schluter and Gnielinski, 1987) Marshall, Colorado, U.S.A. (Cockerell, 1909) Age Unknown Tertiary (Palaeocene) Vladivostok, Russia Wabamun Lake, Alberta, Canada (**) Siam (Thailand) Cochin-China Tertiary (Palaeocene-Eocene) Manchuria, China S.E. coast of England Kamchatka, Russia

* Royal Tyrrell Museum of Paleontology collections. ** Author's field experience.

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copals) as listed in Table 2. Consequently, the potential TABLE 2-Occurrence and age of fossil resins known exists to address questions about changes in terrestrial to contain arthropod inclusions. arthropod diversity and community structure over geologic time within a single preservational matrix. Location Age Reference Significant contributions to resin taphonomy and paleoecology include Larsson (1978) on community compo- New Zealand Pleistocene/Recent Rice, 1980 nents found in samples of Baltic amber, Schluter and Gnei- Tanzania Pleistocene/Recent Schluter and linski (1987) on origin and transport of African copals, and Gnielinski, 1987 Langenheim (1969) on transport and deposition of Hy- Luzon Island Pliocene Durham, 1956 menaea resin in South America. However, in order to apply Australia Pliocene/Pleisto- Hills, 1957 amber inclusions to questions concerning community cene structure and diversity, we need a comprehensive hypoth- Sicily Miocene Brown and Car- esis which outlines taphonomic and diagenetic processes penter, 1978 affecting amber, and a standardized, universally applied Rumania Schluter, 1978 collecting method which allows quantification of collecting Saxony Miocene Schumann, 1984 biases. It is the intent of this paper to provide both, with Mexico (Chiapas) Miocene Quate, 1961 an assessment of the efficiency and biases involved in two Dominican Rep. Oligocene/Miocene Baroni Urbani and principal methods of amber collection. Saunders, 1983 Baltic Sea Oligocene Larsson, 1978 Arkansas (USA) Eocene Saunders et al., TAPHONOMIC MODEL 1974 Burma Eocene Botosaneanu, 1981 Before paleoecological interpretations can be made, pro- Alberta (Can.) Maastrichtian* unpublished cesses which have altered the data base (samples) must Alberta (Can.) Maastrichtian* unpublished be quantified. It is necessary, then, to have a model which Alberta (Can.) Campanian McAlpine and identifies the processes involved so their effects can be Martin, 1969 assessed. A generalized model for amber inclusions is pre- Manitoba (Can.) Campanian(?)** McAlpine and sented in Figure 1, and is discussed below with particular Martin, 1969 emphasis on Alberta amber. In the model "biotic loss" Alaska (USA) Upper Cretaceous Langenheim et al., refers to processes such as decay before burial and con- 1960 sumption by herbivores. The chemical processes which Taymir (Russia) Upper Cretaceous Botosaneanu and result in the polymerization of resin terpinoids, thus form- Wichard, 1983 ing amber, are referred to as amberization. New Jersey (USA) Upper Cretaceous Grogan and Szad- Clearly, in order to address diversity and community ziewski, 1988 structure through samples in resins, we must understand Lebanon Lower Cretaceous Zur Strassen, 1973 how resin acts as a trap. Factors which govern the prob- China uncertain Rice, 1980 ability that an arthropod will become trapped must be Colombia uncertain Cockerell, 1923 identified, and the relationship between a taxon's abun- Zaire uncertain Rice, 1980 dance in resin and its abundance in the ecosystem must be quantified. Hypotheses addressing these concerns are * Material from Edmonton and near Grande Prairie in the Royal Tyrrell Museum of Paleontology. simply generated, but there appear to be no published data which can be used to assess the biases in resin as a trap ** Occurs in a secondary deposit of post-Pleistocene age. Authors argue for this age on the basis of circumstantial evidence. for arthropods. Ample opportunities for the assessment of these biases exist in a wide variety of environments ranging from tropical (Hymenaea resins) to boreal (Pinus, Picea derstanding the meaning of those samples. Once deposited, and related conifers) including close relatives of Metase- resins undergo a series of chemical changes which, to date, quoia which is presumed responsible for production of are not fully understood (see Langenheim, 1969; Lambert Cretaceous resins. and Frye, 1982 for discussions of polymerization pro- Once trapped, an arthropod and its associated resin arecesses). These changes, here called amberization, may af- subject to biotic loss; decay and scavenging, which reduce fect inclusions, resulting in their destruction or decreased the usable systematic information and increase taphon- reliability in identification. omic gain. The identification of these processes and de- Transport, both before and after burial, will result in scription of their effects on samples can significantly in- sorting and will affect distribution of amber and inclusions crease our understanding of paleocommunities. in a manner similar to that of bones in alluvial sediments. In modern forests, resin is a rich source of nutrients and The coal seam in which Alberta amber is found was mined decays rapidly. Identification of environmental factors that for a number of decades, resulting in loss and redistribu- govern its current preservation and incorporation into sed- tion. Tailings from the mining process are subject to wind iments will contribute to our understanding of past en- and water erosion, further obscuring the original concen- vironments. Clarification of the effects these factors have tration in sediments. on resin samples and their inclusions is essential to un- Lastly, each collecting method will introduce unique bi-

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and hand picked (Rice, 1980). The majority of Albertan amber was collected by visually searching coal tailings. Biases in samples produced by methods dependent on human perception will be dependent on the individuals involved in the collecting, and the reason for extracting the sample. An example is the collection of amber for the jewelry trade, in which the scientific value of the amber is secondary.

STUDY AREA AND STRATIGRAPHY

The amber used in this study was collected in Alberta, Canada, near the village of Grassy Lake (see Fig. 2). The precise location is not reported in order to minimize the chances of disturbance by gem collectors and amateur pa- I leontologists, but is available on request from the Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta. The amber originates from a coal seam and associated shales. The stratigraphy, age and paleoecology of the coal seam have been discussed by McAlpine and Martin (1969) and Brown and Pike (1990). It is dated at about 75 Ma (Campanian Stage) and seems to be deposited in situ.

METHODS

Traditionally, amber at this site was collected by wan- dering over the amber-bearing sediments and picking up pieces as they were found. This technique is hereafter called picking. The Royal Tyrrell Museum of Palaeontol- ogy in Alberta holds about 10 kg collected in this manner. Material housed in the Biosystematics Research Centre, Ottawa, Canada, and at the Royal Ontario Museum, To- ronto, Ontario, Canada, was also collected by picking. The method introduced in this paper is an adaptation of bulk sampling for microfossils. Sediment is transported to a water source, placed on a screen and washed to remove fine sediment. The screen is made of 8 mesh premium hardware cloth (stainless steel with 0.65 cm [0.25 in] di- I ameter holes). After washing, material remaining on the screen is transferred to a bin containing salt (NaCI) water with a density of 1.25 g/ml (1.0 kg of salt to 4 1 of water). Amber and recent organic material float in such a solution and are skimmed off the surface. The skimmed material is washed in distilled water and air dried, then placed into a bin of distilled water. This separates the amber, which sinks, from other organic material, which floats. Samples of pure dry amber are weighed before examination for inclusions. This method is henceforth called screening. Every piece of amber was examined under water for external impressions of plants and arthropods and for inclusions near the surface using a binocular microscope with x 12 or x 25 magnification. Amber with no apparent in- FIGURE 1 -Proposed taphonomic model for arthropods preserved in amber. See text for explanation of terms. clusions was tumbled on a lapidary tumbler for 7 days in a successive series of 100, 400, and 600 grits, and subse- quently re-examined for inclusions. The final examination ases. Traditionally, Baltic amber was picked in various was done using a binocular microscope with amber spec- ways from beaches and nearshore sediments or strip mined imens immersed in canola or cedarwood oil. Caution was and hand picked as it was washed from sediment. Amber used with Cedarwood oil because it dissolves younger am- from Burma and the Dominican Republic is also mined bers. Pieces with inclusions were ground on a lapidary

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0 TABLE 3-Mean nodule mass in g for samples collected 0 0 U-M ~~~0 by picking and screening. Bottom line represents the mean for the collecting method with variation indicated 60? by 1 standard deviation.

Picked Screened

0.263 0.0671 0.493 0.0563 0.168 0.0656 0.201 0.165 0.258 ? 0.124 0.0630 ? 0.00585

measuring the mass of amber that floated and did not float in the saltwater bath, with the total mass of each sample calculated by summing floated and not floated masses. To establish the frequency of arthropod inclusions in amber nodules of different masses, nodules from six samples were individually weighed and divided into mass categories. These mass-based samples were processed in the manner described above. The number of inclusions per kilogram and percentage of nodules with inclusions for each mass category were plotted. Nodules in each category were classified as "blisters" (internal manifestations) or as flows (external manifestations) to establish the proportion of external flows in the sample. Periodically, a nugget was found with an aggregation of arthropods far larger than usual. In Albertan amber, up to 40 aphidoid homopterans or 100 mites have been found in a single nodule. These rare occurrences could significantly alter calculations of abundance per kilogram if they occurred within the amber samples used to describe and quantify collecting biases. Such is the case with the mass category 0.70-0.79 g where one nodule contained 25 col- lembolans, two mites, one Psocoptera (wood louse) and one spider. As a result, data are reported in Figure 4 for this sample both with and without this nodule.

RESULTS

The average nodule masses for 3 screened and 5 picked samples are presented in Table 3. Picked samples have FIGURE 2-Location of the Grassy Lake (Alberta) amber deposit cur- consistently larger average nodule masses and greater vari- rently under study. The large circle represents the study site. The city of Calgary is indicated by a small open circle. ation in mean nodule mass among samples. Figure 3 shows the distribution of nodules over the mass categories examined. In picked samples (A) the larger nodule masses wheel with discs of 120 gm and 6 Am. Nodules were pol- have been eliminated from the graph because of the rarity ished on a wet leather block for examination. Arthropod of equivalent nodules in screened samples (0). This trun- inclusions were counted and numbers were converted to cation results in a loss of 0.082 % of screened and 7.36 % yield number of specimens per kilogram. of picked sample data. The smallest mass category con- The average mass of amber nuggets in each sample wastributes a considerably smaller proportion to picked sam- calculated, and the individual pieces in some samples were ples. Picked samples also have many more large nodules massed. Mass categories were established, and the number than screened samples. of amber pieces in each mass category was counted. These Table 4 addresses the question of floatation efficiency. data were then used to produce mass distribution graphs Of 6170.81 g of amber, 6162.59 g were floated, giving an for each collecting technique. The efficiency of the floa- efficiency of 99.87 %. There were no inclusions in the amber tation technique was assessed on 17 picked samples by nodules which were not floated.

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100- TABLE 4-Floatation efficiency of 17 samples in salt water (D = 1.25 g/ml). Overall efficiency is calculated by 90- dividing total mass into mass floated.

80- Sample Floated mass mass Percent i 70A. 70- (g) (g) floated

u') 60 913.86 913.40 99.95 b. 685.89 684.56 99.81 O 1109.99 1109.70 99.97 50 I- 65.74 65.64 99.85 z 304.52 304.48 99.99 c 40- 587.63 583.39 99.28 74.18 74.11 99.91 30 259.39 258.97 99.84 629.93 629.70 99.96 20 256.48 256.33 99.94 85.60 85.58 99.98 305.54 305.54 100.00 10 144.99 144.98 99.99 104.88 104.45 99.59 127.63 127.60 99.98 .05 .15 .25 .35 .45 .55 .65 258.50 258.27 99.91 MASS OF NODULE (G) 256.03 255.89 99.95

FIGURE 3-Distribution of amber nodule masses in picked (A) and Total 6170.81 6162.59 99.87 screened (A) samples. Values for mass categories represent midpoints for each interval.

Number of arthropod inclusions per kg varied between 300 picked and screened samples considerably. Table 5 pre- sents data on a series of screened and picked samples with mean and standard deviation for each collecting method. Screened samples produce more inclusions per kilogram, z z 200- o with about half the variation of picked samples. a Figure 4 describes the percentage of nodules containing inclusions (A) over the range of mass categories for which -i significant numbers of nodules could be collected. The Im number of inclusions found in each mass category (0), z standardized per kg, is also reported in this figure. To- o 100- gether, these data describe the contribution made to the l samples by different nodule masses. Nodules of 0.2 to 0.5 J

z g and 0.75 to 0.95 g are most likely to contain inclusions, z but the number of inclusions per kg is highest for the smallest mass category. As the mass of the nodules in- .05 .15 .25 .35 .45 .55 .65 .75 .85 .S creases, the number of inclusions expected per kg drops from about 300 to about 70. MASS CATEGORY (G) In Alberta, amber is preserved in two forms. There is FIGURE a 4-Abundance of inclusions in different mass categories mea- disc-shaped morph which appears to have been spherical sured as percentage of nodules containing inclusions, and as number at one time. It bears indications of having been flattened, of inclusions per kilogram. Percentage of nodules with inclusions (A) reflects the trapping efficiency of different nodule masses. Number of has no outwardly visible internal structure, and never con- inclusions per kilogram (-) addresses the significance of each mass tains inclusions. Its provenance is uncertain, but due to category for inclusion abundance in a mixed sample. the lack of inclusions, it must be formed within the tree. Blisters are known to occur between the bark and wood in some temperate conifers; at present this seems the most expected to have some effect on the number of inclusions likely origin of these nodules. The morph that contains that category produces. Figure 5 indicates that the pro- inclusions is identical in size and shape with modern ex- portion of external flows in each mass category drops as ternal resin flows, showing little evidence of distortion. The mass of nodule increases, regardless of whether it is mea- proportion of external flows in a given mass category is sured as mass or number of nodules.

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TABLE 5-Number of inclusions per kg for screened .8and picked samples. Average ? standard deviation is given on the bottom line. .7"

> .65- Picked Screened I.- J m .5-

132.7 152.1 m 0 101.8 117.8 A. .4 85.2 130.9 { I z 129.1 136.8 0 .3

92.5 151.8 I

67.4 178.9 .2- 62.8 68.5 .1- 159.8

99.98 ? 28.2 144.72 ? 19.4 I .05 .15 .25 .35 .45 .55 .65 .75 .85 .95 MASS CATEGORY (G)

DISCUSSION FIGURE 5-Proportion of external resin flows expected in different mass categories calculated by mass (A) and by number of nodules In order to assess biases in the screening method, it is (-). Error bars represent 95% confidence limits for mass (pointing necessary to determine how much amber is missed or lost right) and number (pointing left). The numbers of flows in the smaller in the process. Clearly, any amber larger than the diameter mass categories have confidence limits below the resolution of the graph. It is evident that the smaller the mass of a nodule, the greater of the holes in the screen will be transferred to the floa- the probability that it will be a flow. Since flows trap arthropods, a tation bin. Many smaller pieces do not wash through the greater number of flows should be reflected in the number of inclusions screen and are also transferred. The cause may be insuf- per kg for the smaller mass categories. ficient washing, or electrostatic interactions among the amber nodules and water. The mesh size was determined by measuring the smallest diameter of nodules known toclusion is deemed too small. It is also possible that small contain inclusions, and choosing a smaller sized mesh. Con- pieces are rapidly covered by sediment, or that they are sequently, no attempt was made to determine if amber simply not seen. The number of inclusions found in the washed through the screen contained inclusions. This smallest mass category (0.00-0.09 g) and the estimate per omission may introduce a bias which could affect our re- kg indicates that these pieces contain significant inclusions construction of the amber fauna, but knowing the mesh and should not be ignored. In this study, the smallest size size allows the bias to be controlled in comparisons be- of nodule which contained an identifiable inclusion was tween this fauna and others. 0.0031 g. The significance of the small pieces of amber has If 99.87 % of amber in picked samples is floated by the a direct impact on inferences about the paleoecology of salt solution, it is reasonable to assume the same efficiency the amber forest. for screened samples since the process is the same. Such The larger number of inclusions in screened samples can a high efficiency ensures near completeness of amber re- only be due to the smaller pieces of amber. There are three moval from screened sediment, and a tighter correspon- possible reasons for the importance of small pieces. For a dence between amber samples and the population of nod- given mass of resin, small pieces will have a greater surface ules from which they are drawn. The absence of inclusions area available for trapping arthropods and thus may act from amber which did not float and the high floatation as more effective traps. Alternately, small pieces may be efficiency provide a strong foundation for estimates of less effective traps particularly if insects are able to free abundances and species richness. These parameters can themselves from limited volumes of resin, but their abun- then be used with confidence in estimating how well the dance in samples overcompensates, and they contribute amber fauna has been captured by the sampling regime, more inclusions. Figure 4 indicates that when trapping and in paleoecological and paleoenvironmental reconstruc- efficiency is assessed as percentage of nodules with inclu- tions. sions, the smallest mass category has one of the lowest Measurements of average nodule mass of screened sam- efficiencies (1.5 % ). This suggests that it is their abundance ples suggest that there are many more small pieces of which makes smaller pieces significant, and not their trap- amber than previously suspected, based on picked sam- ping ability. ples. This is supported by the distribution of nodules in At the Alberta site studied, amber is found in two forms. the different mass categories in screened samples. Human One represents single or multiple external flows. The sec- collecting bias clearly leans toward larger, more obvious, ond form appears to result from processes occurring inside nodules and away from smaller ones. Perhaps the physical the trunk, similar to blistering, and does not contain in- effort required to retrieve smaller pieces is deemed too clusions. Clearly, the proportion of flows in a given mass great, or the likelihood that such small pieces contain in- category should affect the number of inclusions, assuming

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that all the flows in the sample are subject to the same knowledge, it is impossible to know what a sample of amber insect trapping processes and probabilities. Figure 5 in- inclusions represents. The model also allows quantification dicates that the proportion of flows is essentially constant of the effects of those processes. except for the smallest mass categories. Here, the propor- Grassy Lake amber is found in two forms. One originally tion of flows is considerably higher. Given the above as- spheroid and now flattened never contains inclusions. The sumption, this would act to increase the number of inclu- compression and lack of inclusions in this amber type sug- sions per kg in the 0.05 and 0.15 g categories. gests it formed within trees. The second form is identical With respect to pieces 0.20 g or larger, the cause of their in form with modern external flows. It bears no sign of abundance in picked samples is as yet unclear. It is possible compression, and contains all the inclusions so far located. that they are indeed over-represented in picked samples, Hand collected samples of amber are biased against but it is also possible that erosional forces are insufficient smaller pieces. This results in a concentration of large to transport them to areas where screening has been done. pieces (greater than 0.2 g) beyond their real density. The Considering the large surface area from which picked sam- resulting sample does not accurately reflect the population ples are gleaned, it is reasonable to assume that over- of amber nodules in the sediment. Collection of amber by representation is responsible for their abundance in picked hand also produces samples with fewer inclusions and samples. greater variation in number of inclusions per kg than bulk Variation in mean nodule masses of picked samples is screening with salt water floatation. This is due to variation much larger than in screened samples. This is probably in human search images, the abundance of small pieces, due to variation in the personal biases among collectors. and the higher proportion of small pieces that comprise Different collectors have different search images, which external flows. are being expressed in the variation in mean nodule mass. Standardized collection methods allow the use of amber Paleoecological inferences based on such samples may then inclusions in terrestrial paleoecological reconstruction, and be subject to the same variation if it affects the number provide an alternative criterion for evaluation of hypoth- of inclusions, the taxonomic composition of the inclusions, eses concerning changes in ecosystem structure over time. or the amount of variation in number of inclusions among Consistent use of such methods will yield data which can samples. Table 3 indicates that picking under-represents also be used to evaluate changes of insect diversity over the abundance of inclusions. This is significant for system- time. atics studies as well as paleoecological applications. Vari- ation in number of inclusions per kg is also much higher ACKNOWLEDGMENTS in picked samples, which reduces the strength of inferences for which they are the basis. This research was supported in part by Dr. P. Johnston, Quantification of number of inclusions by mass allows Royal Tyrrell Museum of Palaeontology, Alberta, Canada, the measurement of abundance rather than relying en- and in part by an NSERC grant (#OPG 000 4902) assigned tirely on species richness in paleoecological analyses. This to Dr. G. Pritchard, University of Calgary, Alberta, Can- leads to two new developments in terrestrial paleoecology. ada. Dr. G. Pritchard and Ms. A. Henwood, Cambridge Standard errors of abundance estimates can be tracked as University, England, kindly reviewed the manuscript. mass is added to the total sample, providing a tool for evaluating how completely the fauna is sampled. Addi- REFERENCES tionally, species abundance curves can be plotted, and compared among amber faunas. Comparison of amber fau- AXELROD, D.I., and BAILEY, H.P., 1969, Paleotemperature analysis of nas of different ages becomes possible, as does more di- tertiary floras: Palaeogeography, Palaeoclimatology, Palaeoecol- rectly answering questions about changes in arthropod di- ogy, v. 6, p. 163-195. versity over geologic time, particularly in the context of BANDEL, K., and VAVRA, N., 1981, Ein fossilies Hartz aus der Unter- kreide Jordaniens: Neues Jahrbuch Geologie und Palaeontologie the issue concerning extinction at the K/T boundary. Monatsch, v. 81, p. 19-33. If inclusions are classified by feeding guild rather than BARONI-URBANI, C., and SAUNDERS, J.B., 1983, The fauna of the Do- by taxonomic category, partial trophic reconstruction of minican Republic amber: the present status of knowledge: Trans- ecosystems and the processes which structure them is pos- actions of the 9th Caribbean Geological Conference, v. 1, p. 213- sible. We gain an independent yardstick for evaluating 223. ancient environments and terrestrial ecologies. This in- BArrTTEN, D.J., 1984, Palynology, climate and the development of late Cretaceous floral provinces in the northern hemisphere: in dependent baseline can lead to tests of hypotheses con- BRENCHLEY, P., ed., Fossils and Climate: John Wiley and Sons, cerning changes in ecosystem structure over geologic time p. 127-161. and the importance of various ecological processes at dif- BEHRENSMEYER, A.K., 1975, The taphonomy and paleoecology of Plio- ferent times in the past. Pleistocene vertebrate assemblages of Lake Rudolf, Kenya: Bul- letin of the Museum of Comparative Zoology, v. 146, p. 473-578. BEHRENSMEYER, A.K., 1982, Time resolution in fluvial vertebrate as- CONCLUSIONS semblages: Paleobiology, v. 8, p. 211-227. BEHRENSMEYER, A.K., 1988, Vertebrate preservation in fluvial chan- A taphonomic model describing the origin of ambernels: Palaeogeography, sam- Palaeoclimatology, Palaeoecology, v. 63, ples is necessary for the identification of processes p. 183-199. which influence the composition of those samples. Without BEHRENSMEYER, such A.K., and HILL, A.P., 1980, Fossils in the Making:

This content downloaded from 129.240.204.123 on Thu, 11 Oct 2018 13:20:39 UTC All use subject to https://about.jstor.org/terms AMBER TAPHONOMY 419

Vertebrate Taphonomy and Paleoecology: U. of Chicago press, NISSENBAUM, A., 1975, Lower Cretaceous amber from Israel: Natur- Chicago, 338 p. wissenschaften, v. 62, p. 341-342. BOTOSANEANU, L., 1981, On a false and a genuine caddis-fly from QUATE, L.W., 1961, Fossil Psychodidae (Diptera: Insecta) in Mexican Burmese amber (Insecta; Trichoptera, Homoptera): Bulletin Zoo- Amber: part 1: Journal of Paleontology, v. 35, p. 949-951. logisch Museum Universiteit Van Amsterdam, v. 8, p. 73-78. RICE, P.M., 1980, Amber. The Golden Gem of the Ages: Van Nostrand BOTOSANEANU, L., and WICHARD, W., 1983, Upper-Cretaceous Sibe- Reinhold, Inc. New York, 289 p. rian and Canadian amber caddisflies (Insects; Trichoptera): Bij- SAUNDERS, W.B., MAPES, R.H., CARPENTER, F.M., and ELSIK, W.C., dragen Tot de Deirkunde, v. 53, p. 187-217. 1974, Fossiliferous amber from the Eocene (Clairborne) of the BROWN, V.B., and PIKE, E.M., 1990, Three new fossil phorid flies Gulf Coastal Plain: Geological Society of America Bulletin, v. 85, (Diptera: Phoridae) from Canadian Late Cretaceous amber. Ca- p. 979-984. nadian Journal of Earth Sciences, v. 27, p. 845-848. SCHEIHING, M.H., and PFEFFERKORN, H.W., 1984, The taphonomy of BROWN, W.L., JR., and CARPENTER, F.M., 1978, A restudy of two ants land plants in the Orinoco Delta: A model for the incorporation from the Sicilian amber: Psyche, v. 85, p. 417-423. of plant parts in clastic sediments of Late Carboniferous age of COCKERELL, T.D.A., 1909, Amber in the Laramie Cretaceous: Torreya, Euramerica: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 9, p. 140-142. v. 41, p. 205-240. CREBER, G.T., and CHALONER, W.G., 1984, Climatic indications from SCHLUTER, T., 1978, Fossile Insekten aus dem Pannon von Rubanien: growth rings in fossil woods in BRENCHLEY, P., ed., Fossils and Neues Jahrbuch Geologie und Palaeontologie Monatsch, v. 78, p. Climate: John Wiley and Sons, p. 49-74. 725-733. DANSGAARD, W., 1981, Ice core studies: Dating the past to find the SCHLUTER, T., and GNEILINSKI, F., 1987, The East African Copal-its future: Nature, v. 290, p. 360-361. geologic, stratigraphic, palaeontological significance and compar- DODSON, P., 1971, Sedimentology and taphonomy of the Oldman ison with fossil resins of similar age: National Museums of Tan- Formation (Campanian), Dinosaur Provincial Park, Alberta, zania Occasional Paper 8, 32 p. (Canada). Palaeogeography, Palaeoclimatology, Palaeoecology, SCHUMANN, v. H., 1984, Erstnachweis einer Raubfliege aus dem sach- 10, p. 21-74. sischen Bernstein: Deutsche Entomologische Zeitschrift N. F., v. DOUGLAS, R., and WOODRUFF, F., 1981, Deep sea benthic foraminifera: 31, p. 217-223. in EMILIANI, C., ed., The Sea. v. 7: Wiley, New York, p. 1233- SHEAR, W., BONAMO, P.M., GREIRSON, J.D., ROLFE, W.D.I., SMITH, 1327. E.L., and NORTON, R.A., 1984, Early land animals in North Amer- DURHAM, J.W., 1956, Insect bearing amber in Indonesia and the Phil- ica-Evidence from Devonian age arthropods from Gilboa, N.Y.: ippine Islands: Pan-Pacific Entomologist, v. 32, p. 51-53. Science, v. 224, p. 492-494. FERGUSON, D.K., 1985, The origin of leaf assemblages-New light on SHONFELD, J., SIROCKO, F., and JORGENSEN, N.O., 1991, Oxygen iso- an old problem: Review of Palaeobotany and Palynology, v. 46, tope composition of Upper Cretaceous chalk at Lagerdorf (N. W. p. 117-188. Germany): Its original environmental signal and paleotempera- GERSTEL, J., THUNELL, R.C., ZACHOS, J.C., and ARTHUR, M.A., 1986, ture interpretation: Cretaceous Research, v. 12, p. 27-46. The Cretaceous boundary event in the north Pacific: planktonic SPAHR, U., 1981, Systematischer Katalog der bernstein- und kopal- foraminiferal results from DSDP site 577, Shatsky rise: Paleo- kafer (Coleoptera): Stuttgarter Beitrage zur Naturkunde B, v. 80, oceanography, v. 1, p. 97-117. 107 p. GROGAN, W.L., JR., and SZADZIEWSKI, R., 1988, A new biting midge SPICER, R.A., and WOLFE, J.A., 1987, Plant taphonomy of late Ho- from Upper Cretaceous (Cenomanian) amber of New Jersey (Dip- locene deposits in Trinity (Clair Engle) Lake, northern California: tera: Ceratopogonidae): Journal of Paleontology, v. 62, p. 808-812. Paleobiology, v. 13, p. 227-245. HILLS, E.S., 1957, Fossiliferous Tertiary resin from Allendale, Vic- STEWART, W.N., 1985, Paleobotany and the Evolution of Plants: Cam- toria: Proceedings of the Royal Society of Victoria N. S., v. 69, p. bridge University Press, Cambridge, 405 p. 15-20. TAYLOR, T.N., 1990, Fungal associations in the terrestrial paleoeco- KEILBACH, R., 1982, Bibliographie und list der Arten tierischer system: ein- Trends in Ecology and Evolution, v. 5, p. 21-25. schusse in fossilen Harzen sowie ihrer Aufbewahrungsorte: TRAVERSE, A., 1988, Paleopalynology: Allen and Unwin, Inc., Win- Deutsche Entomologische Zeitschrift, N. F., v. 29, p. 129-286 and chester, Massachusetts, 600 p. v. 29(4-5), p. 301-391. TURNBULL, W.D., and MARTILL, D.M., 1988, Taphonomy and pres- KELLER, G., 1983, Paleoclimatic analysis of Middle Eocene through ervation of a monospecific titanothere assemblage from the Wash- Oligocene planktonic foraminiferal faunas: Palaeogeography Pa- akie Formation (Late Eocene), southern Wyoming-An ecological laeoclimatology, Palaeoecology, v. 43, p. 73-94. accident in the fossil record: Palaeogeography Palaeoclimatology, KOLLMAN, H.A., 1979, Distribution patterns and evolution of gastro- Palaeoecology, v. 63, p. 91-108. pods around the Cretaceous/Tertiary boundary: p. 83-87 in CHRIS- WOLFE, J.A., 1980, Tertiary climates and floristic relationships at TENSEN, K., and BIRKELUND, T., eds., Cretaceous-Tertiary Bound- high latitudes in the northern hemisphere: Palaeogeography, Pa- ary Events II: U. of Copenhagen press, Copenhagen. laeoclimatology, Palaeoecology, v. 30, p. 313-323. LABANDEIRA, C.C., BEAL, B.S., and HUEBER, F.M., 1988, Early insect WOOD, J.M., THOMAS, R.G., and VISSER, J., 1988, Fluvial processes diversification: Evidence from a Lower Devonian bristletail from and vertebrate taphonomy: The Upper Cretaceous Judith River Quebec: Science, v. 242, p. 913-916. Formation, south-central Dinosaur Park, Alberta, Canada. Pa- LAMBERT, J.B., and FRYE, J.S., 1982, Carbon functionalities in amber: laeogeography, Palaeoclimatology, Palaeoecology, v. 66, p. 127- Science, v. 217, p. 55-57. 143. LANGENHEIM, J.H., 1969, Amber: A botanical inquiry: Science, v. 163, ZUR STRASSEN, R., 1973, Insektenfossilien aus der unteren Kreide. 5. p. 1157-1169. Fossile Fransenfluger aus mesozoischen Bernstein des Libanon LANGENHEIM, R.L., SMILEY C.J., and GRAY, J., 1969, Cretaceous amber (Insekten; Thysanoptera): Stuttgarter Beitrage fur Naturkunde from the Arctic Coastal Plain of Alaska: Geological Society of A, 256, 51 p. America Bulletin, v. 71, p. 1345-1356. LARSSON, S.G., 1978, Baltic amber-A paleobiological study: Ento- ACCEPTED JANUARY 19, 1993 monograph, v. 1, 192 p. McALPINE, J.F., and MARTIN, J.E.H., 1969, Canadian amber-A paleontological treasure chest. Canadian Entomologist, v. 101, p. 818-838. -

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