PART 2 Paleogeography And Faunal Dispersal LATE QUATERNARY TECTONICS AND FAUNAL INSULARITY IN SOUTHEAST ASIA

PART 2

LATE QUATERNARY TECTONICS AND FAUNAL INSULARITY IN SOUTHEAST ASIA

Paleogeography And Faunal Dispersal

 

Faunal interchange from one area to the other is possible by way of several types of migration routes as suggested by dermitzakis and Sondaar (1978) as follow :

1. If the faunal interchanges takes place along abroad land conections then this latter is called a corridor. Most the animals can migrate from one area to the other at a time when the land conections exist. In this case there is a balanced fauna in both areas. If the fossil materials on an island indicate a balanced fauna similar to the mainland then the island should have been connected to the mainland then the island should have been connected to the mainland via a corridor in a certain geological period.
2. If the migration can be carried out by some animals but definitely impossible for others then this type of interchange is called a filter dispersal. In this case the dispersal occurs in both directions along a land bridge or other restricted environments such as a peninsula or disconnected part of the area having many barriers, and it take place when the filter bridge is available. In this connection a balanced, but impoverished, fauna exists on the island with a certain percentage of endemic species.
3. If the way of migration is impossible for most of the mainland animals, and very improbable for some species though it may occur accidently, then this type of migration is called a sweepstake. The barriers for this kind of migration could have been a wide sea and it usually takes place in one direction. The fauna of island has an unbalanced character.
4. Another type of migration is called a pendel route. This type of interchange can be carried out easely by some animals but is very difficult for others. The migration takes place in both directions and carried out by good swimmers as well as by flyers, and only when the barrier is not too difficult or is only a narrow channel. The island fauna of this type of migration is unbalanced with species originating from the mainland. In this connection the faunal population of the island will zoogeographically not be isolated from the mainland and in this case endemic forms will not formed on the island.

Although four different types of faunal interchange are suggested as above, overlapping can easely occurs between them. Another very important phenomena, which can be a decisive factor in defining what type of dispersal had taken place in past geological periods were tectonic movements of the earth crust, climatological changes of our globe, sea level fluctuations, and fossilization processes which were subjected to the animal remains. The kinds of fossilizations may destroy, or obliterate entirely, the existence of faunal remains,

Inconnection with faunal dispersal, Azzaroli (1978:17) also suggested that very likely animals do not venter outside their natural environments and their sources of food. For instance no elephas, cervus or hippopotamus will ever go out to swim in the open sea where they know there is no food supply for their existence.

It seems there is a connection between paleogeographic changes and faunal dispersals during the Pleistocene period in southeast asia. This can be seen especially in wallacea region between sunda and sahul shelf.

Towards the end of the upper Pliocene the socalled untere wirbeltier horizont of the kaliglagah fauna is found in Bumiayu region of central java. Characteristic for this fauna is mastodon bumiajuensis. There is also a report mentioning abaout the existence of mastodon bumiajuensis in sangiran (central Java), which is regarded as originating from the corbicula bed of fresh water facies. Another locality of late Pleistocene terrestrial fauna is found in walacea area of south Sulawesi, the socalled archidiscodont-celebochoerus fauna. Based on planktonic foraminifera of the bad directly underlying this fauna its age should be N.19-20. The mixture of terrestrial and marine faunas in sangiran and bumiayu area during the same period. Probably the mixture of the twofacially distinct faunas had something to do with the onset…..