Guano is used as raw material for phosphate-bearing fertilizer as won at the site of exploitation. The hypothesis of these phosphorite to have formed by chemical interaction of bird guano with the underlying (reef ) limestones is widely accepted for the deposits on the islands in the central Pacific and Indian Ocean, such as Nauru and Christmas Islands .

The phosphates of Minjingu, Tanzania deposit formed in a continental basin, filled with sediments of a shallow lake surrounded by inselbergs of Proterozoic rocks Remains of biological concentrations of zooplankton, cichlid fishes and fossil debris, such as fish teeth or bones of cormorants were scattered throughout this lacustrine sequence of Plio-Pleistocene age. Stratification of an open lake produced anoxic bottom conditions. Apart from this soft phosphate ore, another type of phosphorite called hard phosphate ore has been derived from fecal pellets and from excrements of birds reacting with the calcareous bedrock within the Plio-Pleistocene Lake Manyara

Fresh guano is a mixture of nitrate, phosphates, carbonates and organic material.

Diagenesis involves the loss of solubles and the concentration of Ca triphosphate in the topstratum while acidic solutions leaking out of the excrements lead to a replacement of theunderlying bedrock. A type quite similar to these marine phosphates generated by seabirds on islands also evolved in caves on the continent called bat guano owing to the main vertebrate animal producing these excrements.

The crucial question is how old is your guano. If it is older than 40000 years , radiocarbon dating is all in vain . You can apply cosmogenic methods for very young ages expected and you can use U/Pb radiometric age dating if it is, e.g., of Neogene age. Paleontological methods can work but the differentiation of species becomes less pronounced towards younger ages. Take care that you do not obtain mixed-type ages of the bedrock and the newly formed guano.

Dating phosphate can also be hampered by the low U contents of carbonate and hydroxyl apatite s.s.s. The presence of supergene phosphates (APS) derived from the primary guano can help you constrain the age of formation towards younger ages

DILL, H. G., BUSCH, K. and BLUM, N. (1991) Chemistry and origin of veinlike phosphate mineralization, Nuba Mts. (Sudan). - Ore Geology Reviews, 6: 9-24.

DILL, H.G. (1994) Can REE patterns and U-Th variations be used a tool to determine the origin of apatite in clastic rocks?.- Sedimentary Geology, 92: 175-196.

DILL, H.G. and KANTOR, W. (1997) Depositional environment, chemical facies and a tentative classification of some selected phosphate accumulations.- Geologisches Jahrbuch, D 105: 3-43.

DILL, H.G. (2001) The geology of aluminium phosphates and sulphates of the alunite supergoup: A review.- Earth Science Reviews, 53: 35-93.

H.G.Dill

Paul Martin (Univ. Arizona) (and us students) cored bat guano in the Grand Canyon, looking for pre-Industrial Revolution Hg levels. It was funded by NSF, but I don't find it in print. He analyzed pollen in sloth guano also.

Dear Dr. Hammer,

I have listed my piece of advice like a manual to study artifacts abundant in P, Cu, Fe and organic matter in a coastal environment under cool maritime climatic conditions:

1. Age dating: I prefer radio-carbon dating of smelting artefacts such as char coal, organic remains, fecal pellets, lichenology of organic encrustations, and dendrochronology of wooden blanks, logs and fragments wash together and into the caves or along the beach

2. Paleometallurgy of Cu and Fe smelting should have been possible during the past in the Faroes Islands. Use XRD, EMPA and SEM-EDX/WDX

3. Organic matter in a coastal environment under maritime to periglacial climatic conditions

HER/LER method

4. Phosphates: I expect some exotic ammonium phosphates together with the common apatite s.s.s. The degree of crystallinity should be low (experience from South Georgia/South Atlantic and the coastal environment of Chile). XRD, EMPA, SEM/EDX

5. Environment analysis of a rocky coastal environment with natural and artificial/human organic matter

DILL, H.G., KUS J., BUZATU A., BALABAN S.-I. ,KAUFHOLD S., and BORREGO A. G. (2020) Organic debris and allochthonous coal in Quaternary landforms within a periglacial setting (Longyearbyen Mining District, Norway) - A multi-disciplinary study (coal geology-geomorphology-sedimentology).- International Journal of Coal Geology (in print) 3, 5

DILL, H.G. (2009) Pyrometallurgical relics of Pb-Cu-Fe deposits in south-eastern Germany: An exploration tool and a record of mining history .- Journal of Geochemical Exploration, 100: 37-50. 1, 2

DILL, H.G., BÄUMLER, W. and TECHMER, A. (2008) Bronze age mining activities on the Isle of Seriphos, Greece.- Mediterranean Archeology / MEDITARCH, 21: 1-2 2

DILL, H.G., TECHMER, A. and KUS, J (2013) Evolution of an old mining district between 725 and 1630 AD at the boundary between Thüringen and Bayern, SE Germany, using mineralogical and chemical markers, radio-carbon dating and coal petrography of slags.- Archaeological and Anthropological Sciences, 5: 215-233. 1, 2, 3

DILL, H.G. (2008) Geogene and anthropogenic controls on the mineralogy and geochemistry of modern alluvial-(fluvial) gold placer deposits in man-made landscapes in France, Switzerland and Germany.- Journal of Geochemical Exploration, 99: 29-60. 2

DILL, H.G., MELCHER, F., KAUFHOLT, S., TECHMER, A., WEBER, B. and BÄUMLER, W. (2010) Post-Miocene and bronze-age supergene Cu-Pb arsenate-humate/ oxalate- carbonate mineralization at Mega Livadi– Serifos, Greece.- Canadian Mineralogist, 48: 163-181. 1, 1, 3,

DILL H.G., BUZATU A., GOLDMANN S., KAUFHOLD S., and BÎRGĂOANU D. (2020) Coastal landforms of “Meso-Afro-American” and “Neo-American” landscapes in the periglacial South Atlantic Ocean: With special reference to the clast orientation, morphology, and granulometry of continental and marine sediments.- Journal of South American Earth Sciences 98 (on-line). 4, 5

DILL, H.G. (2010) The “chessboard” classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium.- Earth Science Reviews, 100: 1-420. 4 (images)

DILL, H.G., KUS, J., KAUFHOLD, S., RAMMLMAIR, D., and TECHMER, A. (2017) Oligo-Miocene coal in a microtidal environment reworked under Quaternary periglacial conditions (Western Falkland Islands/Isla Gran Malvina). – Coal formation and natural sand processing.- International Journal of Coal Geology 174: 8-22. 1,3,4,5

You will find the various topics in each of the cited papers by the numerical code at the end of the papers .

All papers are available on the RG server upon request

I wish you much success and I am looking forward to your publication on this hot topic which sounds very attractive.

Harald G. Dill