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Mississippian culture pottery is the ceramic tradition of the Mississippian culture (800 to 1600 CE) found as artifacts in archaeological sites in the American Midwest and Southeast. It is often characterized by the adoption and use of riverine (or more rarely marine) shell-tempering agents in the clay paste. Shell tempering is one of the hallmarks of Mississippian cultural practices. Local differences in materials, techniques, forms, and designs are some of the major ways archaeologists understand lifeways, religious practices, trade, and interaction among Mississippian peoples. The value of this pottery on the illegal antiquities market has led to extensive looting of sites. ==Materials and techniques== Mississippian culture pottery was made from locally available clay sources, which often gives archaeologists clues as to where a specific example originated. The clay was then tempered with an additive to keep it from shrinking and cracking in the drying and firing process, usually with ground mussel shells, although in some locations the older tradition of grog tempering, that is, use of crushed up potsherds, persisted into Mississippian times.〔Sturtevant and Fogelson, 538, 540〕 The potters used slab-built construction and the "coiling" method,〔Power, 194〕 which involved working the clay into a long string which was wound round to form a shape and then modeled to form smooth walls, as the potter's wheel was not used by pre-contact Native Americans. Some decoration of the clay was done at this stage by incising, defenstrating, adding shapes, or stamping designs into the wet clay. After the works had dried sufficiently, it was heated in a wood fire. Most pottery found at Mississippian sites is of the variety known as "Mississippian Bell Plain." It is buff colored, contains large fragments of ground mussel shell as a tempering agent, and is not as smooth and polished as finer varieties. Higher quality ceramics feature a finer ground shell as a temper – some instances being so finely ground as to look untempered. Extravagant fine serving wares and grave goods were also produced, with some examples exhibiting handles shaped like animal heads and tails or in the shapes of animal or human forms. Women were probably the makers of pottery, as in most other Native American cultures. Archaeologists found 11 polishing pebbles and a mushroom shaped pottery anvil in the grave of a woman at the Nodena Site.〔 Shell-tempered pottery has long been known to exist in the middle and lower Mississippi Valley by both amateur collectors as well as professional archeologists. "Grave diggers" and amateur collectors have plundered many Mississippian mounds for the fine funerary effigies and other vessels placed as grave goods within mounds and surrounding village areas. Early professional surveys in the valley noted the preponderance of shell-tempered wares in large village sites throughout the valley alluvial plains. Mississippian pottery is easily distinguished from earlier Woodland period pottery. Woodland vessels tend to have thicker walls, flat or conical bases and a large amount of either coarse sand or grog used as temper. Mississippian vessels generally have thinner vessel walls, obvious white flecks of shell temper and round-bottomed pottery forms. For decades archeologists have examined, sorted, described and stored Woodland sherds from those of Mississippian vessels with relative ease. ===Shell tempering=== Shell tempering is a diagnostic criterion in the identification of Mississippian cultures and their ceramic artifacts, excavated site strata and archeological site surveys in general. The record indicates that around 800 CE early populations of Mississippian peoples produced shell tempered pottery in the Central Mississippi Valley at sites, such as the Fairmont Phase at Cahokia and the Early Mississippian strata excavated at the Zebree Site (3MS20) at Big Lake in northeastern Arkansas. In the early 1970s, archeologists working in Northeast Arkansas for the Arkansas Archeological Survey began research into causes of Mississippi Valley potters' relatively sudden shift to shell temper. The team conducted research at the AAS Station Lab at Arkansas State University involving macroscopic, microscopic, petrographic thin-sections, atomic absorption and x-ray diffraction analyses. A member of the team, Michael G. Million, also conducted replicative experiments, perhaps the first to do so with the exact clays, tempers and tools used by prehistoric Mississippian potters. Pastes were created using a variety of temper-to-clay percentages so that vessels as well as test-tiles could be produced for examination. Test tiles gave information about the shrinkage rates of various clay/temper combinations to the 'green' state and then further information upon firing. Simple, round bottom cooking jars were built using coil construction and the Mississippian pottery tool set including a pottery anvil, wooden paddle, mussel shell scrapers and polishing stones. The research discovered that there were very good reasons for using shell tempering for Mississippi Valley clays. The nature of clays formed by such a large meandering river system are distinctive. The huge annually flooded backswamp areas create a clay which is composed of very minute clay particles (primarily silica) and a high proportion of organic content. This is caused by the slow settling or deposition of the alluvial materials after floods. The clay particles tend to measure just a few micrometres in size and in plate-like form. Large amounts of water can be tightly held in the interspace between the clay particles. Add to this the organic ooze, and one has what is known colloquially as "gumbo" clay.〔 Such clay has a high "shrink-swell" ratio depending upon the amount of water present. As it dries from a saturated to a dry state it shrinks greatly – as seen in the cracked clay deposits of drying flooded areas – and this characteristic presents a serious problem to the potter. As the vessel is fired, any water left in the clay will tend to quickly turn to steam and explode the vessel wall in a spawl. It takes care and time to dry these vessels before they can be fired safely. Moreover, as even a well-tempered vessel dries shrinkage rates vary around the contours of the form and will create strains which will crack an air drying vessel if the drying is not slowed and controlled. A high shrinkage rate probably meant lots of effort lost to broken pots in both the drying and firing stages for inexperienced potters and ineffective technologies. Woodland potters attempted to remedy the high shrinkage by using large amounts (up to 33%) of coarse sand and/or grog temper in their efforts to render the clay usable for vessel construction. Moreover, their vessel shapes were necessarily confined to either a flat or conical-bottomed vessel and a thick walled construction were required in order for the vessel to stand, in an unfired state, without collapsing during the air-drying process in preparation for firing. Non-backswamp clays used in many parts of the world could use grog and/or sand and create a round-bottomed vessel, favored by the cook, but not so with the "gumbo" clays of the Mississippi Valley.〔 Another and perhaps even more immediate challenge to the potter using the available backswamp clay is its extreme stickiness, which is called plasticity in ceramic terminology. All but the coarsest of clays are somewhat plastic and malleable in the presence of water; however, the minute clay plate-like particles of backswamp clay are so small that they are influenced by the ionic charges which sit at their edges. The collective ionic charge acts to cause the clay plates to repel each other and thus slip and slide against each other. The shell particles, also plate-like, were produced by the Mississippian potter by collecting then burning freshwater mussel shells, which were originally most likely a byproduct of harvesting the meat for food. The x-ray diffraction of a sample from an unfired lump of pottery clay excavated at the Zebree (3MS20) site confirmed that the shell was burned before being added to the raw clay.〔 Burning the shells eliminates the organic binder and the cooled, burnt shells are easily crushed into a shell temper of fine plate-like particles, some nearly powder. The hinges of the shells are discarded. Using burned shells is logical as unburned mussel shells are hard and very durable. In terms of soil technology, the addition of shell (calcium carbonate) has the effect of neutralizing the ionic charge of the clay particles. During the course of replicative pottery experiments, as the shell was added to the clay in the presence of water, distinct and immediate changes took place in the feel of the clay. With the valence neutral, the clay-temper combination produces a very satisfactory pottery clay. This modification of backswamp clay - particles now clumping instead of constantly slipping - into a well-behaved modeling clay would have been immediately noticed by the experienced prehistoric potter.〔 Adding as little as 10-15% shell temper created an excellent pottery paste that was lighter, stronger and more able to withstand the drying process, and the clay's originally high plasticity was subdued. The calcium carbonate of the freshwater mussels also acts as a binding agent and created a stronger vessel. Thinner coils to make thinner walled vessel were a natural consequence. As the potter was probably also the cook, she was now able to construct a more effective cooking pot. Thinner walls allowed heat to transfer to the food more effectively. A round vessel bottom allows easy stirring of the contents, a more even dissipation of the cooking heat and also permits a more even dispersion of the shock of impacts reducing breakage.〔 The benefits of shell tempered pottery vessels to the Mississippian household were much more efficient utility containers for cooking, particularly the increasing amounts of maize being grown in the valley, and thus sustaining larger and healthier populations in evidence in the archeological record. Around 800 CE, shell tempered pottery spread widely and rapidly from the middle Mississippi River valley to become an integral part of the expanding Mississippian culture and its improved set of technologies for horticulture, hunting and crafting. The bow and arrow, improved corn domestication and the shell tempered pottery wares were major technical advances which, along with widespread trade, contributed to the formation of the advanced chiefdom societies populating the Eastern United States. These interacting chiefdoms were observed by the earliest of European contacts during the mid-16th century. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mississippian culture pottery」の詳細全文を読む スポンサード リンク
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