Arayashiki Shellmound details
- Confirmation report about the structure of shellmound out part, 1976 -
NIPPON ROAD PUBLIC CO., LTD. /Tokyo Daiichi Construction office
Incorporated foundation/Chiba Pref. cultural assets center      
South Arayashiki Shellmound/geographic environment
  1. It is on the tongue state plateau where it is put between Takashina Branched Valley (the west) and Arayashiki Branched Valley (the east) that are open to Yoshikawa River Valley.
  2. Height is around 30 m above sea level. Relative highght with the paddy field face is 19 m.
  3. The branched valleys did not receive the influence of Tokyo Bay. They could obtain the provisions of life in the back plateau.
Arayashiki Shellmound is the horseshoe-shaped shellmound with the diameter of about 150 m opening to the south.
There is not ruin in the center of the shellmound.

The survey result of the shellmound part is as follows.
  • Shellfish: (Many) Ibokisago >> clam >> short-necked clam
  • Fish: (Many) herring >> horse mackerel, mackerel, eel, besides 20 kinds
  • Obsidian: Kouzu Island's (20), Hakone (4)
  • Pollen: cedar (cold climate) >> hackberry family, birch family (mild climate)
  • Plants: knotweed family, hydrophilic plants

The excavation survey of Arayashiki Shellmound in Chiba City was carried out from 1970 due to Keiyo Road (a part of highway network along Tokyo Bay) construction.
The center of the shellmound is the space with no sites. There are not remains of an ancient structure generally. This is considered to be a joint workshop/ meeting place/playground. Now, this place is used in the playground of children and dogs /the kite up convention/summer festival dances . There is a time machine here. When you come here, you may rejuvenate!

The survey result of the shellmound tells, the spiral shellfish called "Ibokisago"(I do not know English name) are overwhelming. This case is similar to Kasori Shellmound about 2 km away from Arayashiki Shellmound. As for the shell in the shellmound, do you think that clam and short-necked clam are main? There are few consumption of Ibokisago now, although the Ibokisago is eaten as the snack for alcoholic drink. Why are there a lot of Ibokisago shells?
1. Was the environment suited to the growth of Ibokisago?
2. Is it easy to manufacture dried shellfish from spiral shellfish than bivalve?

Considering the size of the shellfish, the dried shellfish might have been the seasoning. As they ate boiled food often in Jomon period, dried shellfish may have been used to add salty taste to the cooking.

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