Bulletin of the Geological Society of Malaysia, Volume 70, November 2020, pp. 77 - 86
 

Canggaan transpresi di Bukit C, Guar Sanai: Implikasi terhadap litostratigrafi

(Transpressional deformation of Bukit C, Guar Sanai: Lithostratigraphic implication)

Azrin Azmi, Norasiah Sulaiman*, Muhammad Ashahadi Dzulkafli, Zaiton Harun

Program Geologi, Jabatan Sains Bumi dan Alam Sekitar, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM-Bangi, Selangor, Malaysia
*Corresponding author email address: norasiahs@ukm.edu.my

Abstrak: Jujukan atas Formasi Setul dan jujukan bawah Formasi Kubang Pasu tersingkap dengan baik di Guar Sanai, Perlis akibat daripada aktiviti kuari tanah. Namun, berbanding Bukit B dan Bukit A, singkapan batuan di Bukit C jelas menggambarkan pengaruh struktur terhadap litostratigrafi kawasan tersebut. Sempadan antara Formasi Setul dan Formasi Kubang Pasu ditandai oleh sesar sungkup umumnya berjurus ke utara-selatan hingga timurlaut-baratdaya dan milonit. Jalur sesar sungkup berasosiasi dengan perlipatan dan pengangkatan jelas terbentuk pada zon di antara sesar mendatar ke kiri yang selari (berorientasi baratlaut-tenggara hingga hampir utara-selatan) dan ditafsirkan bagi menampung anjakan di sepanjang zon transpresi. Sesar mendatar ke kiri ini kemudiannya dicangga oleh pergerakan transpresi sesar mendatar ke kanan (berjurus timurlaut-baratdaya dan timur-barat) menyebabkan struktur bertambah kompleks. Kombinasi gerakan lateral dan sungkup membentuk struktur bunga positif yang berasosiasi dengan perlipatan dan pengangkatan, yang sering dijumpai di zon transpresi di rantau sesar mendatar. Canggaan telah mengangkat batuan Formasi Setul yang lebih tua ke kedudukan hampir sama dengan Formasi Kubang Pasu dan menyebabkan anjakan pada kedudukan perlapisan asal serta perulangan jujukan perlapisan. Pembentukan lipatan dan sesar songsang yang berasosiasi dengan pergerakan sesar mendatar ditafsirkan berpunca daripada pergerakan sesar utama di baralaut Semenanjung Malaysia iaitu sesar Bok Bak.

Kata kunci: Guar Sanai, Formasi Kubang Pasu, Formasi Setul, transpresi

Abstract: The upper part of the Setul Formation and the lower part of the Kubang Pasu Formation are well exposed in Guar Sanai, Perlis due to the earth quarry activities. However, compared to the Hill A and Hill B, the outcrops in Hill C clearly illustrates the influence of structure on the lithostratigraphy of the area. The boundary between the Setul Formation and the Kubang Pasu Formation is marked by the thrust fault generally trending north-south to northeast-southwest and mylonite. The thrust belt associated with folding and uplift clearly developed in the zone between parallel lateral faults (trending north-south and southeast-northwest) and is interpreted to accommodate slip along the transpression zone. The sinistral faults are then deformed by transpression movement of dextral faults (trending east-southwest and east-west) which amplified the earlier structures. The combination of lateral and thrust movements formed flower structure that associated with folding and uplift, commonly found in transpressional zone of the strike-slip region. Deformation has caused the older Setul Formation being uplifted to almost equivalent position to the younger Kubang Pasu Formation and led to the displacement of original bed position and repetition of similar sequences. The formation of folding and reverse faulting associated with left lateral strike-slip fault are interpreted to cause by movement of major fault in the northwest Peninsular Malaysia, known as the Bok Bak Fault.

Keywords: Guar Sanai, Kubang Pasu Formation, Setul Formation, transpression

DOI: https://doi.org/10.7186/bgsm70202006