Geochemistry of Tertiary Sequence in Shahbajpur-1 Well, Hatia Trough, Bengal Basin, Bangladesh: Provenance, Source Weathering and Province Affinity

Abstract

Major and trace element compositions of Neogene sandstones and mudrocks from the Shahbajpur-1 (SB-1) well, Hatia trough, Bengal basin, Bangladesh were determined to examine their geochemical characteristics and provenance, in relation to Himalayan uplift, sediment dispersal, and correlation of coeval successions in a basinal context. Major and trace element abundances in the SB-1 succession vary vertically, with SiO 2 content decreasing and Al 2 O 3 increasing from the older (Surma and Tipam Groups) to younger (Dupi Tila Group) sediments. Marked geochemical fractionation between sandstones and mudrocks reflects advanced hydrodynamic sorting, and relative enrichment of several elements (e.g., TiO 2 , Zr, Ce, Th, Cr) suggests sporadic heavy mineral concentration in some sandstones. Major and trace element provenance discriminants indicate a uniform felsic source (Himalayan detritus and recycled sediments) for the entire succession. Values for the Chemical Index of Alteration (CIA) record moderate weathering in the source, and non-steady state conditions produced by Himalayan uplift. Comparison between the Hatia trough samples and coeval Sylhet trough (P2) sediments shows that the more distal SB-1 succession is compositionally more uniform. Strong similarity in geochemical composition between SB-1 and P2 support the hypothesis that the Hatia trough is an extension of P2, fed by the same dispersal system. Key words: Geochemistry, provenance, weathering, sorting, Bengal basin, Bangladesh. mvivsk: GB M ‡elYvq kvnevRcy i-1 (SB-1), nvwZqv Uª vd, e½xq †ewmb, evsjv ‡`k Gi wbIwRb †e ‡jcv_i I K`© g wkjvi cÖ avb I m¦ í cwigv ‡bi †Uª m Dcv`v ‡bi fivmvqwbK ˆewkó¨ Ges Zv ‡`i Drm m¤ú ‡K© aviYv cÖvb Kiv nq Ges Gi m ‡½ wngvj ‡qi ea© bkxjZv, cj ‡ji web¨vm Ges †ewm ‡bi mgmvgwqK wkjv¯- ‡ii m¤úK© wbY© q Kiv n ‡q ‡Q| SB-1 wkjv¯- ‡ii cÖ avb I m¦ í cwigv ‡bi Dcv`vb Gi ch© vßZv Dj− w¤Kfv ‡e wfboe Zvi mv ‡_ SiO 2 Gi cwigvY n« vm Ges Al 2 O 3 e" w×i cÖ eYZv cÖ vPxbZg wkjv¯-i (my igv Ges wUcvg †kª Yx) †_ ‡K bexbZg wkjv¯- ‡i (Wy wc wUjv †kª Yx) †`Lv hvq| †e ‡jcv_i I K`© g wkjvi f-ivmvqwbK web¨¯-Zvq cÖ wZdwjZ nq †h, Dboe ZZi nvB ‡Wª vWvBbvwgK †kª Yx web¨¯-Zv Ges wewfboe Dcv`v ‡bi (TiO 2 , Zr, Ce, Th, Cr) e" w×i cÖ eYZv hv †`Lvq †h, †e ‡jcv_ ‡ii g ‡a¨ wew ¶ßfv ‡e fvix gvwY ‡Ki AvwaK¨| †gRi Ges †Uª m Dcv`vb †`Lvq †h, mg¯-wkjv¯- ‡ii Drm †djwmK (wngvj ‡qi wkjv Ges cỸ© AveZ© b cjj)| †KwgK¨vj AjUv ‡ik ‡bi Bb ‡W· (CIA) Gi cwigvY cÖ gvY K ‡i ga¨g AvenweKvi Mā' Zv Ges Amg my w¯' Z Ae¯' v hvnv wngvj ‡qi Dש ea© bkxjZvi Øviv cwiPvwjZ| Zz jbvgjKfv ‡e nvwZqv Uª v ‡di cjj wm ‡jU Uª vd (P 2 ) Gi cj ‡ji †_ ‡K MVbMZfv ‡e AwaK mgmZ¡ | SB-1 Ges P 2 Gi f-ivmvqwbK MVb cÖ gvY K ‡i †h, nvwZqv Uª vd P 2 Gi ewa© Z Ask hv GKB ai ‡bi cj ‡ji web¨vm Øviv MwVZ|

High-resolution compositional analysis of a fluvial-fan succession: The Miocene infill of the Cacheuta Basin (central Argentinian foreland)

“…confirmed by XRD analyses. Deviation of the measured trend from the IWT may be due to hydrodynamic sorting during sediment transport and deposition, to potassium metasomatism during diagenesis (Fedo et al, 1995;Hossain et al, 2010;Roy and Roser, 2012), and/or to progressive changes in source-rock composition (Nesbitt and Young, 1984;Rieu et al, 2007;von Eynatten et al 2012b; Garzanti and Resentini, 2016). The CIA trend of sandstones from the Mariño and the La Pilona formations however does not follow the pattern to be expected from hydrodynamic sorting (Rieu et al, 2007).…”

Syn-Rift Sandstonеs: The Features of Bulk Chemical Compositions, and Positions on Paleogeodynamic Discriminant Diagrams

“…[Pettijohn et al, 1972], на которой показаны поля граувакк, лититов и сублититов, аркозов и субаркозов, а также кварцевых аренитов. Эта диаграмма чрезвычайно широко используется при литогеохимических исследованиях терригенных образований [Murphy et al, 1996;Das et al, 2006;Dupuis et al, 2006;Svendsen et al, 2007;El-Rahman et al, 2010;Descourvieres et al, 2011;Fatima, Khan, 2012;Roy, Roser, 2012;и др. ].…”

Petrography and Diagenesis of the Tertiary Surma Group Reservoir Sandstones, Bengal Basin, Bangladesh

“…The studied Surma Group sandstones are composed of a variety of major detrital minerals and rock fragments (labile lithic grains) together with some accessory minerals ( Table 1). The framework grains of the analyzed sandstone samples are composed predominantly of quartz (76-91%) and nearly equal amounts of feldspar (3-14%) and rock fragments (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). Several other detrital minerals such as chlorite, muscovite, biotite, calcite and heavy minerals are also found in lesser amounts of the investigated samples.…”

“…The reservoir rock of the Bengal Basin is the Surma Group of Tertiary sandstone (litherenites) comprising quartz (predominant, ~ 60-70%) with lesser amount of feldspars [9,10,11,12]. The sandstones are deposited at the continental margin under the quartzose sedimentary provenance to [12,13].…”

“…These sandstones are good quality reservoir rock with ~20% porosity [14,15,16] and permeability of 200-400 milli darcy [18]. A significant works [9,10,11,12,13,17,18,19,20,21] have been conducted on petrography, geochemistry and isotopic analysis. However, there are limited publications on the sandstone diagenesis of Bengal Basin, although they are mostly based on a particular area of the basin [15,16,17].…”