ISSN:
1573-0417
Schlagwort(e):
Aulacoseira
;
diatomite
;
Tiertiary
;
Thailand
;
palaeogeography
;
lakes
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Geologie und Paläontologie
Notizen:
Abstract The Lampang Basin is the second largest Tertiary graben in northern Thailand and was formed in response to the Himalayan orogeny. Deposition started with Miocene sandstone, lignite, mudstone, shale and oil shale of the Mae Sot Formation, which gave way to Pliocene diatomite, diatomaceous clay and silty clay of the Ko Kha Formation, with coarse clastics being restricted to the basin margins. Secondary iron-staining and iron-rich nodules are also common in the latter formation. Diatoms only occur in the Ko Kha Formation, where they are abundant and well-preserved. Five assemblages, indicative of fresh to moderately alkaline water, are present. These floras are variously dominated by Aulacoseira granulata, A. granulata var. valida, A. agassizi, A goetzeana, A. ambigua, A. italica var. bacilligera and A. italica var. tenuissima. Pennate species are present, but infrequent. During the Pliocene, in the Ban Pa Muang area, non-diatomaceous lacustrine sediments were initially laid down. These gave way to the deposition of diatomaceous clays and diatomites dominated by A. granulata and A. agassizi, which flourished in the deeper and shallower sectors (respectively) of a fresh water body. The palaeolake then became mildly alkaline, with a flora dominated by A. granulata var. valida. Shallow, fresh conditions followed, characterised by varied Aulacoseira diatoms, before the lake again became deeper. This latter phase may be related to increased river recharge.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1008033813344
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