alive and well - Geological Society of Australia

Dana in AustraliaIn November 1839 the ships of the expedition entered SydneyHarbour. The flagship USS Vincennes and the Peacock, with Danaon board, arrived unexpectedly off Port Jackson, slipping into theharbour unannounced and without escort. The corps of civilianscientists aboard the Peacock was not destined to make the nextleg of the voyage, which was Wilkes’s second exploratory attempton the Antarctic landmass. They were instead left in New SouthWales, with orders to rendezvous in New Zealand. This reflectedWilkes’s distrust of this civilian component, being much awarethat he could not impose on them the strict naval discipline thatwas his forte. Dana, however, looked forward to his enforced stayin the colony, feeling that he could “gratify, but partially, thecuriosity, from a geological point of view, which so strange a landmay well excite.”Dana soon met the Reverend WB Clarke — recently arrived inthe colony — and who was eventually to be dubbed the ‘Fatherof Australian Geology’. Taking a coastal steamer to Wollongong,Dana met Clarke there, and together they explored the Illawarradistrict. They made detailed studies of the stratigraphy of bothcoastal and inland sequences. However, the most memorable ofDana’s investigations rests with his study of the factors shapingthe surface of the Earth — an issue distinguished by a greatfluidity of thinking at the time. Dana was a supporter of ‘fluvialism’— the idea that rivers carve out the valleys in which theyrest, rather than merely occupy valleys pre-formed by fissuringof the Earth. His view on the origin of the steep-sided KangarooValley was one that at first agreed with Darwin’s hypothesis, thatthe valleys, and others in the Blue Mountains, were essentiallyarms of the sea. In his report of the expedition’s geology, however,published in 1849, Dana argued that running water was theshaping agent of the valleys, and that the winding inlets of thecoast were ancient stream-cut valleys drowned by risingsea-level.A particularly heated issue of geological concern in theAustralian colony at this time was the age of the coal measuresequences. This had become an area of serious conflict (see TomVallance’s detailed documentation) with the major protagonists,WB Clarke and Frederick McCoy, adopting entrenched anddivergent positions. Clarke, although he appears to have been themore flexible of the two, considered strata beneath the coalysequences to be conformable, and the entire sequence to beDevonian or Early Carboniferous in age. McCoy, later appointedChair of Natural History at the University of Melbourne, claimedan unconformity to exist between the sequences, and that thecoals were of ‘oolitic’ age — that is, much younger than those ofEurope. Dana, in his travels in the Illawarra with Clarke, and withothers in the Hunter region, lent towards a conformable view.When his notes on the geology of New South Wales werepublished in the expedition reports in 1849, Dana concluded, onthe basis of field evidence and on previously collected fossils,that an Upper Carboniferous or Lower Permian age for the coalswas most likely — an estimate close to present thinking, althoughthe story is complex. In 1882 Dana was awarded the ClarkeMedal by the Royal Society Of New South Wales.Global synthesesand the Divine CreatorThe US Exploring Expedition returned to Sydney from Antarcticain March 1840, and Dana rejoined the Peacock. This vessel,carrying the scientific corps, returned to the USA to map partsof the west coast, but was wrecked at the mouth of the ColumbiaRiver. Although all hands were saved, many reports and scientificresults of the expedition were lost. In 1842, Dana establishedhimself first in Washington, later in New Haven, where the preparationand writing of the massive scientific reports were tooccupy him for the next 13 years. Many short articles on a varietyof subjects also appeared during this time, although many of thetopics that later engaged him are foreshadowed in the reports.Prominent among these was his interest in volcanic islands andcoral reefs. In some senses he felt that Darwin had pre-emptedhim here, but Dana pushed understanding of these linkedphenomena much further. Dana added information to Darwin’sobservations about factors controlling reef growth, andimportantly, in the case of volcanic islands, showed the ageprogression and subsidence of islands within linear chains in thePacific by noting the state of erosion of individual islands.James Dwight Dana. Image courtesy of Yale University Art Gallery.26 |TAG September 2012