Mid Cenozoic freshwater wetlands of the Sunda region

Abstract

Sunda region was the scene of widespread rifting during the mid-Cenozoic, resulting in the development of numerous large lakefilled rifts, analogous in scale to the rift valley system of East Africa. The Tonle Sap in Cambodia forms the closest modern analogue for these lakes in the Southeast Asian region. Many of the palaeolakes were long lived, continuing uninterrupted as open lakes for several millions of years during the Oligocene. Smaller rift systems infilled with fluvial sediments, but the majority remained as lakes, and with Late Oligocene subsidence, were transformed by brackish, and in the earliest Miocene, by marine incursion, into large inland seas. These seas reached their greatest extent at the time of the mid Miocene thermal maximum. This paper describes the development and eventual demise of these lakes following marine transgression, and, based on their rich content of pollen and spores, illustrates the variety of fresh and brackish water swamp communities which developed around their margins. The marginal swamps can be divided into: i) seasonally inundated swamps, mainly during the Oligocene, characterised by Barringtonia, Lagerstroemia and grasses/sedges; ii) fern swamps from the Late Oligocene onward; iii) alluvial swamps, often characterised by Pandanus; and iv) peat swamps. The latter can be differentiated into kerapah peat swamps, first occurring during the Oligocene, and basinal peat swamps, becoming widespread from the Early Miocene onward.

Tropical Amphi-Pacific disjunctions in the Cladocera (Crustacea: Branchiopoda)

“…We found Leydigiopsis in swamps in Thailand habitats which have a highly relictual character (Morley, 2013;Morley and Morley, 2013) often from deforested regions harbouring significant endemism and diversity. The habitat clearly plays an important role in cladoceran evolution (Van Damme et al, 2013b).…”

The palaeogeography of Sundaland and Wallacea since the Late Jurassic

“…4) it appears that much of Sundaland was topographically low. Rivers fed clastic sediments to the Sundaland margins of Sumatra, Java, SE Borneo and Sarawak, implying a still elevated interior which included Shoup et al (2012) and Morley and Morley (2013) from the integration of an extensive seismic and biostratigraphic database. It is likely that the Malay peninsula was an elevated region supplying sediment to Sunda shelf basins, and the Schwaner mountains of SW Borneo was another.…”

Inland swamps in South East Asia harbour hidden cladoceran diversities: species richness and the description of new paludal Chydoridae (Crustacea: Branchiopoda: Cladocera) from Southern Thailand

“…The peat swamp habitat is ancient and covered much larger areas in SE Asia in the past, when also the diversity of swamp types was much larger than it is today (e.g. Miocene to Pliocene) (Morley, 2000;Morley and Morley, 2013). In this study, we comment on swamp habitats in SE Asia as an underestimated habitat for cladocerans.…”

“…Surveys that distinguish between the different swamp types still remain to be carried out. As they constitute different habitats with specific histories and ecologies (Morley, 2000;Morley and Morley, 2013), the various swamp types are likely to harbour different cladoceran communities. For example, Alona sarasinorum, was found in Kaekae peat swamp in Pattani province (Tab.…”

“…. They could be ancient species, that evolved in swamp ecosystems when the habitat covered much larger areas in SE Asia (Cenozoic; Morley and Morley, 2013). However, on top of these obvious new species, a significant cryptic diversity can be expected among the swamp-inhabiting taxa that belong to widespread species complexes that are in need of taxonomical revision.…”