Seismic Expression of the Cenozoic Mass Transport Complexes, Deepwater Tarfaya-Agadir Basin, Offshore Morocco

Abstract

The Tarfaya-Agadir Basin in offshore Morocco is a frontier exploration area with no deepwater industry well penetrations and limited well control in the updip shelfal equivalent. Recent detailed 3D seismic mapping and study by Shell has identified the presence of two large mass transport complexes (MTCs) in the Tertiary interval, in addition to a number of smaller and younger MTCs. The large MTCs, named Tejas A and Tejas B, exhibit distinct seismic characteristics that may be significant to understanding the evolution of the basin during the Tertiary. The basal Tejas A is characterized by numerous kilometerscale, coherent transported blocks. The size and quantity of transported blocks observed in Tejas A is unique in Morocco and the Atlantic Margin. The MTC in the younger Tejas B is a thick chaotic unit with distinctive downdip erosional lobes. This deposit is overlain by high amplitude, parallel seismic facies. The chaotic seismic facies is often sharp-edged, with well-defined pressure ridges. Only a few small transported blocks and erosional remnants have been observed in Tejas B. Failure deposits account for a significant percentage of the Tertiary stratigraphic interval in the 3D survey area.

Carbonate platforms in wedge-top basins: An example from the Gunung Mulu National Park, Northern Sarawak (Malaysia)

“…13A, B), thought to be derived from a nearby shelfal setting to the NE and displaced downslope in a southwestward direction. Particularly well-imaged analog occurrences of rafted blocks, based on 3D seismic data, have been described from the Moroccan Atlantic margin by Lee et al (2004).…”

MTD distribution on a ‘passive’ continental margin: The Espírito Santo Basin (SE Brazil) during the Palaeogene

“…Beaubouef and Abreu, 2010;Booth et al, 2003;Prather et al, 1998;Sawyer et al, 2007;Winker and Booth, 2000), West Africa (Deptuck et al, 2007;Gee et al, 2006;Heinio and Davies, 2006;Lee et al, 2004) or Brazil (Alves, 2010;Silva et al, 2010). Characterizing the limits (lateral and vertical) between stratified units and MTDs, and their relation to underlying structures, can provide insights of the distribution and compartmentalization of reservoir-prone lithologies.…”

Distribution and characterization of failed (mega)blocks along salt ridges, southeast Brazil: Implications for vertical fluid flow on continental margins

“…Over growing salt diapirs, overburden strata is commonly either thinned or completely removed by erosional processes, which accumulate eroded strata in peripheral salt withdrawal basins [Giles and Lawton, 2002]. Mass transport deposits (or MTDs) resulting from these erosional processes are usually mud dominated and have low exploration potential [Lee et al, 2004;Moscardelli et al, 2006;Posamentier and Kolla, 2003], except when sand-rich strata is present [Armitage et al, 2009;Beaubouef and Abreu, 2010;Davison et al, 2000b;Dunlap et al, 2010;Moraes et al, 2007;Moscardelli and Wood, 2008;Piper et al, 1997;Shanmugam et al, 1996;Tripsanas et al, 2008]. Important factors controlling the seal competence of MTDs include the presence of a strong structural fabric (including faults) in their interior, and variations in the degree of remobilization experienced by failed strata [Frey-Martínez et al, 2006].…”

“…Debris flows are characterized by presenting highly disaggregated strata and no preservation of internal strata within a cohesive matrix [Masson et al, 2006]. Large blocks of remnant or rafted strata can be ubiquitous within the latter classes of submarine landslides, either close to the MTD source areas or transported to toe regions of submarine landslides through gravitational processes such as hydroplaning [Deptuck et al, 2007;Dunlap et al, 2010;Ilstad et al, 2004;Lee et al, 2004;Minisini et The location of the BES-2 3D seismic data set used in this study is represented by the black rectangle. (b) Coherence slice taken 20 ms TWTT above Horizon 1, intersecting the studied MTD.…”

“…[4] Rafted blocks have been comprehensively identified in the vicinities of salt structures, either derived from local failures [Davison et al, 2000a;Tripsanas et al, 2004] or distant (upslope) landslides [Dunlap et al, 2010;Lee et al, 2004]. However, no data has been yet presented on the effect of salt diapirs on slope stability, nor the impact of such remnant/rafted strata on fluid flow has been yet assessed for a key case study.…”