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Depositional Environment of the Kinta Limestone, Western Peninsular Malaysia

Abstract

The Kinta Limestone occurs in the western stratigraphic zone of Peninsular Malaysia, where it comprises 65 percent of the Palaeozoic section exposed in Kinta Valley. Due to the effects of contact metamorphism, few efforts have been made to define the depositional environment of the Kinta Limestone. These rocks were part of a continental block, the Sibumasu Terrane, that drifted from northwestern Gondwana in Early Paleozoic time and reached its current position adjacent to a suture zone with the Indochina Terrane in Permian time. The Kinta Limestone was deposited in a passive continental margin setting along with several siliciclastic units deposited from Ordovician through Late Permian time. Subduction of the Western Belt (Sibumasu Terrane) beneath the Central Belt, which is derived from the Indochina Terrane and marked by the Bentong-Raub suture zone, resulted in emplacement of granite intrusive beneath and east of the Kinta Limestone during Triassic through Jurassic time. The carbonate rocks are generally metamorphosed, and most of the primary sedimentary features are destroyed. This region is characterized by tower karst hills and hot springs. Careful examination of the Kinta Limestone indicates that numerous sedimentary features survived metamorphism in the northern part of Kinta Valley. In this area the unit is medium- to dark-gray, fine-grained, thinly bedded limestone with sharply defined bedding planes and preserved slump features. It contains few fossils, lacks benthic fossils entirely, and contains a sparse conodont fauna. The dark color suggests a high organic content. There are thin-bedded cherts interbedded with the limestone. Detrital siliciclastic debris is absent from the limestones, which have a low silica composition (SiO2<2.5 wt. %) and a generally marine minor cation composition (Mn/Sr averages 2.21 wt. %, σ = 0.44, n= 4). The texture, lack of detrital siliciclastic grains, and preserved sedimentary structures in the Kinta Limestone suggest deposition in a low energy, slope environment. The high organic content and lack of benthic fauna indicate a low oxygen setting. Therefore, the mudstone dominated Kinta Limestone with bedded cherts was likely deposited in a slope environment with considerable contribution of semipelagic and pelagic sediments.