TYPHOONS AND HAINAN ISLAND, CHINA

Australian scientists based at ANU in 1975 made contact with Chinese colleagues at Academica Sinica. There was a mutual interest in Quaternary geology, human prehistory, and environmental change.  I was at ANU at the time and took part in discussions about exchange visits. My desire to be included in the initial trips to look at coastal sites was not acceptable to the Chinese Academy until 1981. These exchanges continued into the mid-1980s allowing a team from Academica Sinica working on coastal problems to visit Australia and for me to go to China on two occasions.

In 1981, John Chappell at ANU arranged for Don Wright, then at Sydney University, and me at UNSW Duntroon, to visit China and to later serve as hosts for return visits. “Coasts and coral reefs” constituted a broad theme of interest forming an inter-university activity unlike the others which just involved ANU staff. Our group was guided on a two-week field trip around Hainan Island by Professor Huang and his colleagues from the South China Sea Institute of Oceanology, Guangzhou; we also gave lectures at Academica Institutes in Guangzhou, Beijing, and Nanjing.

Unlike current relations between China and Australia, our exchanges were undertaken in a very welcoming, cordial, and open atmosphere. We felt we had lots to learn as Chinese science in certain areas of Quaternary geology and human prehistory research had been a closed book for several decades. There had been a period when a close working relationship with Soviet Russia had allowed many senior scientists to learn Russian. Those contacts had ceased in the mid-60s. Very little was known about coastal studies and we were delighted that those from the South China Institute were keen for us to visit and discuss with them our recent findings and look at their field sites. We were escorted at all times but were able to engage in productive and very courteous discussion on a range of topics. Both sides were very grateful for the opportunities made possible by the exchanges.

In some respects our trip around Hainan Island located off the southern tip of China, was a “magical mystery tour”. We never were quite sure what was coming next nor where we would stop and what we would see. Yet once at a site we had great fun exploring the outcrops, walking the beaches, swimming/snorkelling across reef flats, and engaging with locals. Our hosts were alarmed at times when Don and I took off to swim out to sea to examine the reefs; this had not been a form of field work they were used to! We also found we were a source of attraction to local children many of whom had never seen Caucasian people; my hairy arms were touched by many kids and they were also fascinated by a camera as shown in the attached photo. Remember this was 1981! Our hosts also insisted that during the day we had to “rest”. So for 2 hours each afternoon we retired to a cool room to chat and write up notes.

Hainan gets battered by high seas and storm surges during typhoons. Don Wright and Wei Wu in their recent paper on the Pearl River Delta and Guangzhou coast discuss the risk of typhoon-induced disaster in this general region (see Chapter 12 in Wright and Reid Nichols, Tomorrow’s Coasts: Complex and Impermanent, Springer, 2019). They cite the work of Liu et al. (2001) who analysed historic records of typhoons noting that they were frequently grouped into multi-decadal periods. The suggestion was made in that 2001 paper that we could now be entering a period of increased frequency in the decade beginning 2020; well we just had two typhoons this past month off the Chinese coast!

Our tour of Hainan revealed evidence of significant deposition of clastics derived from reefs along the southern half of the island. This contrasted with the lower energy deltaic landscape to the north such as near the city of Haikou where we encountered mangroves. The southern coast possesses fringing coral reefs and reef flats littered with blocks torn from the reef edge. We spent some time looking at a site east of Sanya (Da Dong Hai Bay). There were few living corals on these flats although we did see a few microatolls. The reef slope down to c 8m contained a lot of rubble as well as a variety of living hard and soft coral types. My notes tell me that one of my esteemed colleagues thought the area had been hit by a typhoon within the last 20 years producing the detached blocks. At a nearby site, we have a photo (attached) of this colleague (John Chappell) standing outside a building damaged by a recent typhoon. Our hosts did not have any specific records to help us with dating of these events.

We inspected several exposures cut into cliffs composed of late Quaternary carbonate sediments. In some places, the Institute had radiocarbon dates on coral debris of mid- Holocene age. This was the case near Sanya on the southwest end of Lui Hai Tou Peninsula. Here we found a 4m high cliff cut into cemented coral rubble with dates c. 3600-3750 yrs BP (unit B). As shown in my sketch this unit was plus 2m thick overlying what we called unit C consisting of large broken coral fragments around HWM with a single date of 4345 yrs. At this site, there was an in-situ reef within the current intertidal range with dates between 4800 and 5180 yrs BP (unit D). Our Chinese colleagues were most interested in our views of this site as it raised many questions on conditions at time of deposition including the magnitude of storm surges responsible for the reworking of what must have been a prolific reef environment in the mid-Holocene.

Early on in the tour of Hainan we were taken to a cliff face on the west coast ostensibly to see erosion of a basalt section. Much to our surprise this site near Gan Chong village turned out to be a magnificent exposure of what was most likely an Interglacial sequence. I attach my field sketch of an 8m cliff face which we divided into 5 units (A to E). Our hosts had not studied this site and no material had been dated. We had lots of fun trying to interpret what we could see in the time available. A buried soil (unit C) suggested a time discontinuity in the sequence and the cover sand (unit A) was quite indurated. Clear evidence of shell and coral debris at elevations up to 6 to 8m suggested a higher sea level at the time of deposition. This turned out to be the only time on the trip where we encountered clear evidence of undisputed higher sea levels along with high energy wave deposits of Pleistocene age.

Sadly, we never got to properly write up the observations from this 1981 trip. Perhaps in the interim these sites have been studied in detail; I am not aware of such work. I am happy to share these notes with anyone who is interested.

What these exchanges showed was the mutual respect in sharing knowledge and making friends with scientists who had been isolated for over a decade. To learn about how typhoons could impact a coast and produce such high-level deposits of reef material was an eye-opener for me. Diversity of environments around this island made for great discussion and I thoroughly enjoyed the companionship of those two remarkable coastal scientists, John Chappell and Don Wright, even though their pipe smoking drove me nuts at times!

Bruce Thom

Words by Prof Bruce Thom. Please respect the author’s thoughts and reference appropriately: (c) ACS, 2020. For correspondence about this blog post please email austcoastsoc@gmail.com 

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