Examination of deep guano deposits in Jamaican caves

 

Prepared by Ronald S. Stewart, Jamaican Caves Organisation (JCO)

 

August 31, 2012

 

 

Summary:

 

Samples of guano were collected at two sites, Schwallenburgh Cave, St Ann, and Home Away From Home Cave, in Trelawny, by Ronald S. Stewart of the JCO, Chris Grooms of Queens University, and Wieslaw Bogdanowicz of the Polish Museum & Institute of Zoology, during early March, 2012, with no objection from the landowners (Forestry and UCRusal). Preliminary analysis has been carried out by the aforementioned institutions. Full analysis will take place over the course of the next year, and when results are received, they will be forwarded to NEPA.

 

Schwallenburgh Cave:

 

The site consists of a 49m shaft to a chamber that contains deep deposits of guano, located near Faiths Pen, St Ann, at [Restricted], WGS84; [Restricted], JAD2001. The surrounding land has been continuously occupied for over a century, and has been utilized in one manner or another by humans since the 17th century. The chamber where the deposits are found takes water occasionally during very heavy rains, but the current morphology indicates only a minor flow along only one side of the deposit.

 

On March 6, 2012, Stewart and Grooms descended the shaft to carry out the sampling. Bogdanowicz stayed at the top. A narrow trench was dug into the part of the deposit that had the most horizontal strata, and 80 samples of ~1cm each were taken and deposited into individual bags. The lowest point was the actual bottom of the pure deposit, at ~1m deep. All samples were given the prefix SCH. Care was taken to ensure minimal disturbance to the overall deposit.

 

Home Away from Home Cave:

 

The site consists of two large chambers, and is located in the Cockpit Country, south of Pantrepant, at [Restricted], WGS84; [Restricted], JAD2001. A 20m vertical descent from the main entrance gives access to the first chamber. The main guano deposit, which is the subject of this report, is in the second chamber. The surrounding land has never been settled. Logging has taken place in the past, but not intensively. Input of water to the second chamber is by way of percolation only.

 

On March 8, Stewart and Grooms descended into the cave to carry out the sampling, while Bogdanowicz remained at the top. A narrow trench, 1m deep, was cut into the deposit at what Grooms judged to the best point, and layers of ~1cm depth were removed and deposited into individual bags. Sampling was limited to a depth of 25cm because of stickiness in the material, and difficulty cleaning the tray between samples. One additional sample was taken at a depth of 1m. The total depth of the deposit, determined by way of pushing a rod to the bottom, is ~2m. All samples were given the prefix HOM. Care was taken to ensure minimal disturbance to the overall deposit.

 

Results:

 

Preliminary radiocarbon dating was carried out on two samples from each site.

 

The deposits at Schwallenburgh Cave were found to be of relatively recent origin (100 BP, +/-40), and could not be accurately dated by this method. However, contaminant analysis, which will be performed in the future, should establish the time-frame of deposition.

 

At Home Away From Home Cave, the age of the deposits was much greater. Sample HOM 25-26cm was dated to Cal BP 1400 1300 (2 Sigma, 95% probability), or 550 650 AD. Sample HOM ~100cm was dated to Cal BP 3460 3360 (2 Sigma, 95% probability), or 1510 1410 BC.

 

 

Preliminary conclusions:

 

The lack of ancient deposits at Schwallenburgh, as compared to Home Away From Home, may indicate that there is an occasional (approximately once per century) flushing of the deposits by flooding during heavy rains (extreme tropical storm events). It may, or may not, have been exacerbated by deforestation in the 19th century - future analysis of the samples may supply information on this. A second possibility is that the cave was mined for guano about 100 years ago, despite the difficulties involved in accessing it by way of the 49m deep shaft. However, there were no artefacts present that would confirm this. What can be said is that the morphological suitability of the cave as a bat roost has not changed in at least thousands of years, and if there had been no disturbance of any sort, there should be extant deposits of the same order of age as those at Home Away.

 

The deposits at Home Away From Home are of great interest, and when analysis is complete may supply good information on the natural history of the site for the last 1500 years, and a snapshot of conditions at 3,500 years ago. It should also be noted that the total depth of the deposit is twice what was sampled, and due to increasing compaction with depth, the age of the lowest layers will be on the order of 8,000 to 10,000 years old. The author of this report, who is the principal investigator for the JCO, has, of August, 2012, visited over 300 speleological sites in Jamaica, and knows of no other guano deposits as deep as those at Home Away. Most bat caves are much easier to access, and have had any deep deposits removed by mining. Home Away From Home Cave is unique, and deserving of official protection.