Skip to main content Accessibility help
Hostname: page-component-568f69f84b-gcfkn Total loading time: 0.22 Render date: 2021-09-21T21:35:20.574Z Has data issue: true Feature Flags: { "shouldUseShareProductTool": true, "shouldUseHypothesis": true, "isUnsiloEnabled": true, "metricsAbstractViews": false, "figures": true, "newCiteModal": false, "newCitedByModal": true, "newEcommerce": true, "newUsageEvents": true }

Article contents

Modeling shelliness and alteration in shell beds: variation in hardpart input and burial rates leads to opposing predictions

Published online by Cambridge University Press:  08 April 2016

Adam Tomašových
Institut für Paläontologie, Würzburg Universität, Pleicherwall 1, 97070 Würzburg, Germany. E-mail:
Franz T. Fürsich
Institut für Paläontologie, Würzburg Universität, Pleicherwall 1, 97070 Würzburg, Germany. E-mail:
Thomas D. Olszewski
Department of Geology and Geophysics and Faculty of Ecology and Evolutionary Biology, Texas A&M University, College Station, Texas 77843. E-mail:


Distinguishing the differential roles of hardpart-input rates and burial rates in the formation of shell beds is important in paleobiologic and sedimentologic studies, because high shelliness can reflect either high population density of shell producers or lack of sediment. The modeling in this paper shows that differences in the relative importance of burial rates and hardpart-input rates lead to distinct patterns with respect to the degree of shelliness and taphonomic alteration in shell beds. Our approach substantially complements other models because it allows computation of both shelliness and assemblage-level alteration. To estimate shelliness, we dissected hardpart-input rates into dead-shell production and shell destruction rates. To estimate assemblage-level alteration, we computed an alteration rate that describes how rapidly shells accrue postmortem damage. Under decreasing burial rates but constant hardpart-input rates, a positive correlation between alteration and shelliness is expected (Kidwell's R-sediment model). In contrast, under decreased destruction rates and/or increased dead-shell production rates and constant burial rates (Kidwell's R-hardpart model), a negative correlation between shelliness and alteration is expected. The contrasting predictions thus provide a theoretical basis for distinguishing whether high shell density in shell beds reflects passive shell accumulation due to a lack of sediment dilution or whether it instead reflects high shell input from a life assemblage. This approach should be applicable for any fossil assemblages that vary in shell density and assemblage-level alteration. An example from the Lower Jurassic of Morocco, which has shell-rich samples less altered than shell-poor samples, suggests that the higher shelliness correlates with higher community-level abundance and lower proportion of juveniles of the main shell producer, supporting the driving role of hardpart-input rates in the origin of the shell-rich samples in this case. This is of significance in paleoecologic analyses because variations in shelliness can directly reflect fluctuations in population density of shell producers.

Copyright © The Paleontological Society 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Abbott, S. T. 1997. Mid-cycle condensed shellbeds from mid-Pleistocene cyclothems, New Zealand: implications for sequence architecture. Sedimentology 44:805824.CrossRefGoogle Scholar
Abbott, S. T. 1998. Transgressive system tracts and onlap shellbeds from mid-Pleistocene sequences, Wanganui Basin, New Zealand. Journal of Sedimentary Research 68:253268.CrossRefGoogle Scholar
Allmon, W. D. 1993. Age, environment and mode of deposition of the densely fossiliferous Pinecrest Sand (Pliocene of Florida): implications for the role of biological productivity in shell bed formation. Palaios 8:183201.CrossRefGoogle Scholar
Allmon, W. D., Spizuco, M. P., and Jones, D. S. 1995. Taphonomy and paleoenvironment of two turritellid-gastropod-richbeds, Pliocene of Florida. Lethaia 28:7583.CrossRefGoogle Scholar
Beckvar, N., and Kidwell, S. M. 1988. Hiatal shell concentrations, sequence analysis, and sealevel history of a Pleistocene coastal alluvial fan, Punta Chueca, Sonora. Lethaia 21:257270.CrossRefGoogle Scholar
Callender, W. R., Powell, E. N., and Staff, G. M. 1994. Taphonomic rates of molluscan shells placed in autochthonous assemblages on the Louisiana continental slope. Palaios 9:6073.CrossRefGoogle Scholar
Callender, W. R., Staff, G. M., and Parsons-Hubbard, K. M., et al. 2002. Taphonomic trends along a forereef slope: Lee Stocking Island, Bahamas. I. Location and water depth. Palaios 17:5065.2.0.CO;2>CrossRefGoogle Scholar
Cantalamessa, G., Di Celma, C., and Ragaini, L. 2005. Sequence stratigraphy of the Punta Ballena Member of the Jama Formation (Early Pleistocene, Ecuador): insights from integrated sedimentologic, taphonomic and paleoecologic analysis of molluscan shell concentrations. Palaeogeography, Palaeoclimatology, Palaeoecology 216:125.CrossRefGoogle Scholar
Carroll, M., Kowalewski, M., Simões, M. G., and Goodfriend, G. A. 2003. Quantitative estimates of time-averaging in terebratulid brachiopod shell accumulations from a modern tropical shelf. Paleobiology 29:381402.2.0.CO;2>CrossRefGoogle Scholar
Clarke, K. R., and Green, R. H. 1988. Statistical design and analysis for a “biological effects” study. Marine Ecology Progress Series 46:213226.CrossRefGoogle Scholar
Davies, D. J., Powell, E. N., and Stanton, R. J. Jr. 1989. Relative rates of shell dissolution and net sediment accumulation—a commentary: can shell beds form by the gradual accumulation of biogenic debris on the sea floor? Lethaia 22:207212.CrossRefGoogle Scholar
Doyle, P., and Macdonald, D. I. M. 1993. Belemnite battlefields. Lethaia 26:6580.CrossRefGoogle Scholar
Enos, P. 1991. Sedimentary parameters for computer modeling. Kansas Geological Survey Bulletin 233:6299.Google Scholar
Flessa, K. M., and Kowalewski, M. 1994. Shell survival and time-averaging in nearshore and shelf environments: estimates from the radiocarbon literature. Lethaia 27:153165.CrossRefGoogle Scholar
Flessa, K. M., Cutler, A. H., and Meldahl, K. H. 1993. Time and taphonomy: quantitative estimates of time-averaging and stratigraphic disorder in a shallow marine habitat. Paleobiology 19:266286.CrossRefGoogle Scholar
Fürsich, F. T., and Aberhan, M. 1990. Significance of time-averaging to palaeocommunity analysis. Lethaia 23:143152.CrossRefGoogle Scholar
Fürsich, F. T., and Oschmann, W. 1993. Shell beds as tools in basin analysis: the Jurassic of Kachchh, western India. Journal of Geological Society, London 150:169185.CrossRefGoogle Scholar
Fürsich, F. T., and Pandey, D. K. 2003. Sequence stratigraphic significance of sedimentary cycles and shell concentrations in the Upper Jurassic-Lower Cretaceous of Kachchh, western India. Palaeogeography, Palaeoclimatology, Palaeoecology 193:285309.CrossRefGoogle Scholar
Geary, D. H., and Allmon, W. D. 1990. Biological and physical contributions to the accumulation of strombid gastropods in a Pliocene shell bed. Palaios 5:259272.CrossRefGoogle Scholar
Glover, C. P., and Kidwell, S. M. 1993. Influence of organic matrix on the post-mortem destruction of molluscan shells. Journal of Geology 101:729747.CrossRefGoogle Scholar
Gutiérrez, J., Jones, C. G., Strayer, D. L., and Iribarne, O. O. 2003. Mollusks as ecosystem engineers: the role of shell production in aquatic habitats. Oikos 101:7990.CrossRefGoogle Scholar
Heinrich, R., and Wefer, G. 1986. Dissolution of biogenic carbonates: effects of skeletal structure. Marine Geology 71:341362.CrossRefGoogle Scholar
Holland, S. M. 1995. The stratigraphic distribution of fossils. Paleobiology 21:92109.CrossRefGoogle Scholar
Holland, S. M. 2000. The quality of the fossil record: a sequence stratigraphic perspective. In Erwin, D. H. and Wing, S. L., eds. Deep time. Paleobiology 26(Suppl. to No. 4):103147.CrossRefGoogle Scholar
Jaanusson, V. 1972. Constituent analysis of an Ordovician limestone from Sweden. Lethaia 5:217237.CrossRefGoogle Scholar
Kidwell, S. M. 1985. Palaeobiological and sedimentological implications of fossil concentrations. Nature 318:457460.CrossRefGoogle Scholar
Kidwell, S. M. 1986a. Models for fossil concentrations: paleobiologic implications. Paleobiology 12:624.CrossRefGoogle Scholar
Kidwell, S. M. 1986b. Taphonomic feedback in Miocene assemblages: testing the role of dead hardparts in benthic communities. Palaios 1:239255.CrossRefGoogle Scholar
Kidwell, S. M. 1989. Stratigraphic condensation of marine transgressive records: origin of major shell deposits in the Miocene of Maryland. Journal of Geology 97:124.CrossRefGoogle Scholar
Kidwell, S. M. 1991. The stratigraphy of shell concentrations. In Allison, P. A. and Briggs, D. E. G., eds. Taphonomy: releasing the data locked in the fossil record. Topics in Geobiology 9:115129. Plenum, New York.Google Scholar
Kidwell, S. M. 1993. Taphonomic expressions of sedimentary hiatuses: field observations on bioclastic concentrations and sequence anatomy in low, moderate and high subsidence settings. Geologische Rundschau 82:189202.CrossRefGoogle Scholar
Kidwell, S. M. 1998. Time-averaging in the marine fossil record: overview of strategies and uncertainties. Geobios 30:977995.CrossRefGoogle Scholar
Kidwell, S. M., and Jablonski, D. 1983. Taphonomic feedback: ecological consequences of shell accumulations. In Tevesz, M. J. S. and McCall, P. L., eds. Biotic interactions in recent and fossil benthic communities. Topics in Geobiology 3:195248. Plenum, New York.Google Scholar
Kondo, Y., Abbott, S. T., and Kitamura, A., et al. 1998. The relationship between shellbed type and sequence architecture: examples from Japan and New Zealand. Sedimentary Geology 122:109127.CrossRefGoogle Scholar
Kowalewski, M., Goodfriend, G. A., and Flessa, K. W. 1998. High-resolution estimates of temporal mixing within shell beds: the evils and virtues of time-averaging. Paleobiology 24:287304.Google Scholar
Kowalewski, M., Serrano, G. E. A., Flessa, K. W., and Goodfriend, G. A. 2000. Dead delta's former productivity: two trillion shells at the mouth of the Colorado river. Geology 28:10591062.2.0.CO;2>CrossRefGoogle Scholar
Meldahl, K. E., Flessa, K. W., and Cutler, A. H. 1997. Time-averaging and postmortem skeletal survival in benthic fossil assemblages: quantitative comparisons among Holocene environments. Paleobiology 23:207229.CrossRefGoogle Scholar
Miller, A. I., and Cummins, H. 1990. A numerical model for the formation of fossil assemblages: estimating the amount of post-mortem transport along environmental gradients. Palaios 5:303316.CrossRefGoogle Scholar
Miller, A. I., and Cummins, H. 1993. Using numerical models to evaluate the consequences of time-averaging in marine fossil assemblages. In Kidwell, S. M. and Behrensmeyer, A. K., eds. Taphonomic approaches to time resolution in fossil assemblages. Short Courses in Paleontology 6:151168. Paleontological Society, Knoxville, Tenn. Google Scholar
Morse, J. W., Mucci, A., and Millero, F. J. 1980. The solubility of calref and aragonite in seawater of 35%0 salinity at 25°C and atmospheric pressure. Geochimica et Cosmochimica Acta 44:8594.CrossRefGoogle Scholar
Naish, T., and Kamp, P. J. J. 1997. Sequence stratigraphy of sixth-order (41 k.y.) Pliocene-Pleistocene cyclothems, Wanganui Basin, New Zealand: a case for the regressive systems tract. Geological Society of America Bulletin 109:978999.2.3.CO;2>CrossRefGoogle Scholar
Nebelsick, J. H., and Kroh, A. 2002. The stormy path from life to death assemblages: the formation and preservation of mass accumulations of fossil sand dollars. Palaios 17:378393.2.0.CO;2>CrossRefGoogle Scholar
Noe-Nygaard, N., Surlyk, F., and Piasecki, S. 1987. Bivalve mass mortality caused by toxic dinoflagellate blooms in a Berriasian-Valanginian lagoon, Bornholm, Denmark. Palaios 2:263273.CrossRefGoogle Scholar
Olszewski, T. D. 1999. Taking advantage of time-averaging. Paleobiology 25:226238.CrossRefGoogle Scholar
Olszewski, T. D. 2004. Modeling the influence of taphonomic destruction, reworking, and burial on time-averaging in fossil accumulations. Palaios 19:3950.2.0.CO;2>CrossRefGoogle Scholar
Parras, A., and Casadío, S. 2005. Taphonomy and sequence stratigraphic significance of oyster-dominated concentrations from the San Julián Formation, Oligocene of Patagonia, Argentina. Palaeogeography, Palaeoclimatology, Palaeoecology 217:4766.CrossRefGoogle Scholar
Powell, E. N. 1992. A model for death assemblage: can sediment shelliness be explained? Journal of Marine Research 50:229265.CrossRefGoogle Scholar
Powell, E. N., Staff, G. M., Davies, D. J., and Callender, W. R. 1989. Macrobenthic death assemblages in modern marine environments: formation, interpretation, and application. Reviews in Aquatic Sciences 1:555589.Google Scholar
Radley, J. D., and Barker, M. J. 1998. Palaeoenvironmental analysis of shell beds in the Wealden Group (Lower Cretaceous) of the Isle of Wight, southern England: an initial account. Cretaceous Research 19:489504.CrossRefGoogle Scholar
Sanders, D. 2003. Syndepositional dissolution of calcium carbonate in neritic carbonate environments: geological recognition, processes, potential significance. Journal of African Earth Sciences 36:99134.CrossRefGoogle Scholar
Schäfer, K. 1969. Vergleichs-Schaubilder zur Bestimmung des Allochemgehalts bioklastischer Karbonatgesteine. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 1969:173184.Google Scholar
Soja, C. M., Gobetz, K. E., and Thibeau, J., et al. 1996. Taphonomy and paleobiological implications of Middle Devonian (Eifelian) nautiloid concentrates, Alaska. Palaios 11:422436.CrossRefGoogle Scholar
Staff, G. M., Callender, R. W., and Powell, E. N., et al. 2002. Taphonomic trends along a forereef slope: Lee Stocking Island, Bahamas. II. Time. Palaios 17:6683.2.0.CO;2>CrossRefGoogle Scholar
Tomašových, A. 2004. Postmortem durability and population dynamics affecting the fidelity of brachiopod size-frequency distributions. Palaios 19:477496.2.0.CO;2>CrossRefGoogle Scholar
Tomašových, A., Fürsich, F. T., and Wilmsen, M. 2006. Preservation of autochthonous shell beds by positive feedback between increased hardpart-input rates and increased sedimentation rates. Journal of Geology (in press).Google Scholar
Yesares-García, J., and Aguirre, J. 2004. Quantitative taphonomic analysis and taphofacies in lower Pliocene temperate carbonate-siliciclastic mixed platform deposits (Almería-Níjar basin, SE Spain). Palaeogeography, Palaeoclimatology, Palaeoecology 207:83103.CrossRefGoogle Scholar
Cited by

Send article to Kindle

To send this article to your Kindle, first ensure is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

Note you can select to send to either the or variations. ‘’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Modeling shelliness and alteration in shell beds: variation in hardpart input and burial rates leads to opposing predictions
Available formats

Send article to Dropbox

To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

Modeling shelliness and alteration in shell beds: variation in hardpart input and burial rates leads to opposing predictions
Available formats

Send article to Google Drive

To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

Modeling shelliness and alteration in shell beds: variation in hardpart input and burial rates leads to opposing predictions
Available formats

Reply to: Submit a response

Please enter your response.

Your details

Please enter a valid email address.

Conflicting interests

Do you have any conflicting interests? *