Bulletin of the Geological Society of Malaysia, Volume 38, Dec. 1995, pp. 91 – 108
Jabatan Geologi, Universiti Kebangsaan Malaysia, Bangi, 43600
Abstrak: Lapisan Nenering merupakan batuan sedimen termuda yang tersingkap di kawasan Pengkalan Hulu, Grik. Sebaran sedimen dan sedimentologi jelas menujukkan sedimennya telah dienapkan oleh sistem aluvium di dalam lembangan bendungan sesar yang berarah utara selatan. Sedimennya telah diterbitkan dari batuan sekitar yang lebih tua (Kumpulan Baling) dan diangkut ke dalam lembangan menuruni tebing-tebing sesar. Sebaran fasies secara menyisi jelas menunjukkan kehadiran sedimen konglomerat di bahagian pinggir lembangan dan fasies berubah secara beransur kepada batu pasir dan lodak ke bahagaian paksi lembangan. Organisasi fasies menegak jelas menunjukkan aliran sedimen tercair dan sungai-sungai efemeral merupakan mekanisma pengangkut yang utama.
Kewujudan aliran yang tidak malar di dalam sistem aluvium tersebut telah mendorong pembentukan beberapa ufuk tanah. Usianya yang secara relatif muda membolehkan kesemua fitur dan profil tersebut terawet dengan baik dan telah dikenalpasti. Kajian terhadap sampel-sampel paleosol menunjukkan hubungan petrografi dan geokimia yang baik. Empat zon utama di dalam profil paleosol telah dikenalpasti dengan menggunakan kaedah pencirian petrografi dan geokimia tersebut.
Kehadiran kalkret pedogenik di dalam paleosol tersebut dikaitkan dengan fasa iklim lebih kering berbanding dengan masa sekarang.
Abstract: The Nenering Bed is the youngest sedimentary rock outcropping in the Pengkalan Hulu, Grik area. Its distribution and sedimentology show that the sediments were deposited by an alluvial system in a fault-bounded basin which trends north-south. The sediments were derived from the adjacent older sedimentary formations (the Baling Group) and were transported down the fault scarps into the basin. Lateral facies distribution clearly shows the presence of conglomerate at the basin edge which grades gradually into sandstone and silt towards the basin axis. Vertical facies organisation clearly shows that ephemeral streams were the dominant transportation mechanism.
The occurrence of periodical flow in the alluvial systems allowed the formation of soil horizons during dryer periods. The relatively younger age of the sediment had allowed the soil features and profile to be well preserved. Studies of samples from the paleosol horizons show good petrographic and geochemical correlation. Four major zones in the paleosol‘s profile have been identified using petrographic characterization and geochemistry.
The presence of pedogenic calcretes in the sediment sequence is interpreted to represent a period of dryer climate during its formation.
https://doi.org/10.7186/bgsm38199509
