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Archaeologist excavate units in cave entrance

Ireland Cave

Site ID: 15Jf830

Kentucky Archaeological Survey
Unless specified, we cannot provide site location information.


​​​​​​Ireland Cave sits within a northeast-facing limestone outcrop. The cave entrance encloses an area of approximately 1260 square feet.  

Archaeologists systematically excavated four units at the site. They placed two units east of the northern cave opening. Work there revealed that this area had been the cave's northern entrance when Native Americans stayed there ca. 6000 BC.  Over time, however, erosion of the overlying rocks caused the cave roof to collapse, covering the original cave opening and sealing the archaeological deposits. The other units sampled deposits in the current northern cave opening, and deposits located slightly downslope from the former northern cave opening.​

A Middle Archaic hearth.


Analysis of the vertical distribution of temporally diagnostic spear points, supported by radiocarbon dates from carbonized nutshell fragments, revealed that Native peoples lived at Ireland Cave primarily during the Middle Archaic period - from 6000 to 4000 BC.  During repeated short visits, they collected and processed large amounts of hickory nuts, and hunted white-tailed deer, squirrels, pond/box turtles, groundhogs, rabbits, raccoons, and other animals.​​

During these visits, they likely also collected locally available raw materials, such as Muldraugh chert, for making chipped stone tools. Nodules of this chert ​had weathered out of the limestone cliffs and eroded into nearby streams.

Investigators documented several surface hearths and charcoal dumps. The hearths were spots of burned and reddened soil, sometimes surrounded by limestone rocks. Native peoples would have used surface hearths for cooking meals and for processing nuts. Charcoal dumps were concentrations of debris from cleaning-out and reusing hearths.

Middle Archaic Knob Creek spear points.

What's Cool?

​Im​pacts of Climate Change and People

The climate of the Midcontinental United States from circa 7000 to 2200 BC was generally warmer and drier than today's. Forested areas shrank and open grasslands expanded. This period is called the Hypsithermal Climatic Optimum. In deposits at archaeological sites, this period is represented by evidence for increased soil erosion and deposition​.

Archaeologists encountered similar evidence for the Hypsithermal Climatic Optimum in the soils at Ireland Cave. The graph to the right illustrates the cave’s sedimentation record over time.

The steep line shows that erosion near the cave, and thus soil deposition within it, increased dramatically from 5600 BC to 4000 BC. The less steep line at the top of the graph indicates that deposition slowed from 4000 to 1000 BC. This suggests that a more stable landscape had developed near the cave, and thus, that less erosion occurred.

​The information from Ireland Cave suggested that perhaps natural or human-set fires created open vegetation on the hillside surrounding the cave. This would have lead to increased erosion. ​But the extensive human use of the cave over time also could have impacted the surrounding vegetation. People likely trampled the grasses, plants, and shrubs during their stays, and this could have contributed to erosion around the cave opening, too.

​​From these data, researchers inferred that environmental fluctuations and human use of the cave during the Middle Archaic caused soil erosion in the area around the cave and thus soil deposition inside the cave itself.​

Sedimentation graph showing rapid accumulation of soil from 5600 to 4000 BC.

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