Kilbaha Bay Ross Fm


Kilbaha Bay
 
Panarama  of channel and sheet turbidite sandstones at Kilhaha Bay this and other photos in the gallery below are by Christopher Kendall, and Peter Haughton.

West end of Kilbaha Bay with outcrop of Mid-Ross Sandstone Formation in the background and in the forground the wave cut pavement of the intertidal zone. West end of Kilbaha Bay with outcrop of channeled Mid-Ross Sandstone Formation in the background and in the forground the wave cut pavement of the intertidal zone. West end of Kilbaha Bay with Keatings Bar and Kilbaha Village in the background and in the forground the wave cut pavement of the intertidal zone. Pebble Beach at West end of Kilbaha Bay with Keatings Bar and Kilbaha Village in the background. Pebble Beach Kilbaha Bay just east of Keatings Bar and Kilbaha Village. Wave cut platform incised into the jointed Ross Formation sandstones exposed on the foreshore of Kilbaha Bay. Wave cut platform incised into the jointed and gently rippled bedding plane surface of the Ross Formation sandstones exposed on the foreshore of Kilbaha Bay. Wave cut platform incised into the bedding plane surface of the Ross Formation sandstones exposed on the foreshore of Kilbaha Bay. The surface shows potential evidence of megaflutes and a cover of rounded boulders and pebbles. Note the channeled sands in the low cliffs above. Wave cut platform incised into the Ross Formation sandstones exposed on the foreshore of Kilbaha Bay. Surface cover of rounded boulders and pebbles heaped against the channeled sands of the low cliffs above. Wave cut platform incised into the Ross Formation sandstones exposed on the foreshore of Kilbaha Bay. Surface of bedding plane shows jointing and local rippling. West end of Kilbaha Bay with outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs in the background and in the forground the wave cut pavement of the intertidal zone. West end of Kilbaha Bay with outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs in the background with Keatings bar in distance. In the forground is the wave cut pavement of the intertidal zone. Also note Pleistocene glacial drift at top section filled the Pleistocene eroded surface of the Carboniferous. West end of Kilbaha Bay with outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone. Also note Pleistocene glacial drift at top section filled the Pleistocene eroded surface of the Carboniferous. West end of Kilbaha Bay with outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone with rounded blocks and pebbles heaped over this. Also note Pleistocene glacial drift at top section filled the Pleistocene eroded surface of the Carboniferous. Kilbaha Bay with outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone with rounded blocks and pebbles heaped over this. Also note Pleistocene glacial drift at top section filled the Pleistocene eroded surface of the Carboniferous. Deepwater channeled sands of the Ross Formation interbedded with shale above the wave-cut platform in the east of Kilbaha Bay. Note storm surge beach gravels heaped against cliff and the Pleistocene glacial drift gravels at top of section. Interbedded deepwater channeled sands and shales of the Ross Formation above the wave-cut platform at Kilabaha. Top of section are Pleistocene glacial drift gravels. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Deepwater channeled sands of the Ross Formation interbedded with shale above the wave-cut platform in the east of Kilbaha Bay. Note storm surge beach gravels heaped against cliff to the right and the vegitated Pleistocene glacial drift gravels at top of section. Amalgamated deepwater channeled sands of the Ross Formation overlying and interbedded with shale at their eroded base in Kilbaha Bay. Note vegitated Pleistocene glacial drift gravels at top of section. Base of amalgamated deepwater channeled sand of the Ross Formation overlying and interbedded with shale at its eroded base. Note chute or lens like sand fill on underlying topography below the channel. Base of amalgamated deepwater channeled sand of the Ross Formation overlying and interbedded with shale at its eroded base. Note chutes or lens like sand fills interbedded with shale on underlying topography below the channel. Base of amalgamated deepwater channeled sand of the Ross Formation overlying and interbedded with shale at its eroded base. Note chutes or lens like sand fills interbedded with shale on underlying topography below the channel. Base of amalgamated deepwater channeled sand of the Ross Formation overlying and interbedded with shale at its eroded base. Note chutes or lens like sand fills interbedded with shale on underlying topography below the channel. Note deepwater runneling on wave cut platform to right. Base of amalgamated deepwater channeled sand of the Ross Formation overlying and interbedded with shale at its eroded base. Note chutes or lens like sand fills interbedded with shale on underlying topography below the channel. Note deepwater runneling on wave cut platform to right. Kilbaha Bay with outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone,Note Pleistocene glacial drift at top section filled the Pleistocene eroded surface of the Carboniferous. Kilbaha Bay details of outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone, Kilbaha Bay details of outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone, Bedding planes marked by thin shales. Kilbaha Bay details of outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone, Kilbaha Bay details of outcrop of channeled Mid-Ross Sandstone Formation in the low cliffs above the wave cut pavement of the intertidal zone, Interbedded channeled sand lobes Ross Fm West Kilbaha Bay and overbank shales. Note soft sediment deformation and scouring at the base of the channeled sand lobes. The scallopped character of some of the sands suggestive of megaflutes scouring their surfaces. Amalgamated channeled sand lobes with some interbedded overbank thin shales of Ross Fm West Kilbaha Bay Scouring and soft sediment deformation at the base of the channeled sand lobes of the Ross Formation on the West side of Kilbaha Bay Channeled sand lobe scoured into thin interbedded shales and sands of the Ross Fm West Kilbaha Bay. Scouring and soft sediment deformation at the base of the channeled sand lobes of the Ross Formation on the West side of Kilbaha Bay. Note thin interbedded shales and sands between the channeled lobe sands. Soft sediment deformation and scouring at the base of the channeled sand lobes of the Ross Formation on the West side of Kilbaha Bay. Soft sediment deformation occurs in the thin interbedded shales and sands below channeled lobe sands. Soft sediment loading and deformation at the base of the channeled sand lobes of the Ross Formation on the West side of Kilbaha Bay Amalgamated channeled sand lobes of Ross Fm West Kilbaha Bay with shale partings eroded into thinner interbedded shales and sands. Channeled sand lobe of Ross Fm West Kilbaha Bay over thinner interbedded channel sand lobes. At top of section is Pleistocene glacial drift. Amalgamated sands of channel margin in the channeled lobe of the Ross Formation of West Kilbaha, over thinner interbedded channel sand lobes. At top of section is Pleistocene glacial drift. Amalgamated sands of channel margin in the channeled lobe of the Ross Formation of West Kilbaha, over other thinner interbedded sand lobes. Amalgamated sands of channel margin in the channeled lobe of the Ross Formation of West Kilbaha, over other thinner interbedded sand lobes. Detail of channel margin in the channeled sand lobes of the amalgamated Ross Formation of West Kilbaha Bay. Detail of channel margin in the channeled sand lobes of the amalgamated Ross Formation of West Kilbaha Bay. Above are gravels of Pleistocene glacial drift. Channel margin in the channeled sand lobes of the Ross Formation of West Kilbaha Bay. Note Pleistocene glacial drift at top section filled the Pleistocene eroded surface of the Carboniferous. Eroded base of an amalgamated channeled sand lobe of Ross Fm West Kilbaha Bay. Note shaley fill beneath the channel. Top of section is a channel margin in the amalgamated channeled sand lobe of the Ross Formation of West Kilbaha Bay. Below are thinner bedded amalgamated channeled sand lobes of Ross Formation. Note shaley partings of overbank setting interbedded with the channel sands. Amalgamated channeled sand of the Ross Formation of West Kilbaha Bay. Note shaley parting interbedded with the channel sands at the base of section to right. Amalgamated channeled sand of the Ross Formation of West Kilbaha Bay. Below is a further bedded channel sand. Note rounded beach cobbles generated by the Atlantic storm surges that beat against these low cliffs. Above is Pleistocene glacial drift at top section filling the eroded Pleistocene surface on the Carboniferous. Sediment loading and scouring at the base of Channeled Sand Lobes in the Ross Formation on the West side of Kilbaha Bay Amalgamated channeled sand of the Ross Formation of West Kilbaha Bay. Below is a further bedded channel sand. Note rounded beach cobbles generated by the Atlantic storm surges that beat against these low cliffs. Above is Pleistocene glacial drift at top section filling the eroded Pleistocene surface on the Carboniferous. Amalgamated channeled Sand Lobes Ross Fm West Kilbaha Bay. Sediment loading and scouring at the base of Channeled Sand Lobes in the Ross Formation on the West side of Kilbaha Bay In forground to the right is a megaflute scour in the channeled sand lobes Ross Fm West Kilbaha Bay. Above are Interbedded channeled sand lobes and overbank shales. Channeled Sand Lobes Ross Fm West side Kilbaha Bay At base of small cliff to the right is the margin of megaflute in the Ross Formation on the West side of Kilbaha Bay. Above are the amalgamated sands of a deepwater channeled sand lobe. At top of section are interbedded amalgamated sands of deepwater channeled sand lobes. At base of section is a megaflute in the Ross Formation on the West side of Kilbaha Bay. At base of section is a megaflute in the Ross Formation on the West side of Kilbaha Bay. At top of section are interbedded amalgamated sands of deepwater channeled sand lobes. At base of the ledge in the foreground is a chute scour filled by deepwater interbeds of thin sands and shale. The top of section exhibits sand lobes and interbeds of shale, At base of the ledge in the mid foreground is a chute scour filled by deepwater interbeds of thin sands and shale. The top of section exhibits sand lobes and interbeds of shale, At base of section to center of section is a megaflute in the Ross Formation on the West side of Kilbaha Bay. At top of section are interbedded amalgamated sands of deepwater channeled sand lobes and overbank shales.. Interbedded channeled sand lobes and overbank shales of the Ross Formation on the West side of Kilbaha Bay. Base of section to left is the eroded edge of a megaflute to left and the onlapping fill. Detail of scoured margin of a megaflute in the Ross Formation on the West side of Kilbaha Bay. The megaflute fill onlaps the eroson surface and is composed of thin interbeds of shale and sand. Thin interbeds of deepwater shale and sand sandwiched between slightly thicker sands of the Ross Formation on the West side of Kilbaha Bay. Sand lobe and channel detail including rippled sand beds interbedded with thin flaser bedded sands with thin mud drapes of the Ross Formation of the west side of Kilbaha Bay. Dewatering structures in the sand lobe and channel facies of the Ross Formation of Kilbaha Bay. Deepwater sand beds interbedded with thin flaser bedded sands with thin muds of the Ross Formation of the west side of Kilbaha Bay. Sand Lobe and Channel Detail Ross Fm Kilbaha Bay Deepwater sand beds, some with dewatering structures interbedded with thin flaser bedded sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand bed interbedded with thin flaser bedded sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded sands and thin muds of the Ross Formation of the west side of Kilbaha Bay Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded sands and thin muds of the Ross Formation of the west side of Kilbaha Bay Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded and rippled sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded and rippled sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded and rippled sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded and rippled sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded and rippled sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded and rippled sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Deepwater sand beds with some dewatering deformation and interbedded with thin flaser bedded and rippled sands and thin muds of the Ross Formation of the west side of Kilbaha Bay. Westward view of amalgamated deepwater channel sands of the Ross Formation interbedded with shales. Westward view of amalgamated deepwater channel sands of the Ross Formation interbedded with shales. Note vegitated Pleistocene glacial drift gravels at top of section. Amalgamated deepwater channel sands of the Ross Formation interbedded with shales. Note vegitated Pleistocene glacial drift gravels at top of section. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Base of a deepwater channeled sand of the Ross Formation where the weight of the implacement of the amalgamated channel fill has caused soft sediment deformation, displacing and folding the sands interbedded with shale. Amalgamated deepwater channel sand of the Ross Formation at top of section overlying interbedded shales and sands, some of the latter to the right pinching out where they are eroded, probably the margin of a megaflute. Amalgamated deepwater channel sand of the Ross Formation at top of section overlying interbedded shales and sands, some of the latter to the right pinching out where they are eroded, probably the margin of a megaflute. Amalgamated deepwater channeled sands of the Ross Formation, At base of the ledge is a chute scour surface beneath the deepwater channel fill. The megachute is inturn filled by interbedded shales and sands. Amalgamated deepwater channeled sands of the Ross Formation, At base of the ledge is a chute scour surface beneath the deepwater channel fill. The megachute is inturn filled by interbedded shales and sands. Amalgamated deepwater channeled sands of the Ross Formation interbedded with shale. At base of the ledge is a chute scour surface beneath the deepwater channel fill. To the right the wave cut platform shows deepwater runnels and soft sediment deformation caused by the emplacement of overlying sediment. Amalgamated deepwater channeled sands of the Ross Formation interbedded with shale. At base of the ledge is a chute scour surface beneath the deepwater channel fill. Amalgamated deepwater channeled sands of the Ross Formation interbedded with shale. At base of the ledge is a chute scour surface beneath the deepwater channel fill. Amalgamated deepwater channeled sands of the Ross Formation interbedded with shale. At base of the ledge is a chute scour surface beneath the deepwater channel fill. To the right the wave cut platform shows deepwater runnels and soft sediment deformation caused by the emplacement of overlying sediment. Wave cut platform of the eastern portion of Kilbaha Bay. Amalgamated deepwater channeled sands of the Ross Formation interbedded with shale. At base of the ledge is a chute scour surface beneath the deepwater channel fill.

Kilbaha Bay-Architecture of Deepwater Sheet Lobes and Channels in Mid-Ross Sandstone Formation
 
Outcrops at the Kilbaha Bay on north west shore of Shannon Estuary east of Loop Head expose the nature of the deepwater sediments of the Ross Formation where they are characterized by channeled deepwater fan lobes, megaflutes and channel fill. As at the Bridges of Ross there are a series of incised and stacked channels with channel fill that extends beyond the channels as wings and are associated with megaflutes (Elliot , et al, 2000; & Elliott, 2000) which can be identified in the image galleries.
 

As explained in the 2008 SEPM Field Guide (Martinsen et al., 2008) Kllbaha Bay is flanked by low cliffs that provide a continuous 1.6 km well-exposed outcrop above a wave-cut intertidal platform oblique to depositional strike and in which the channelized-sheets can be seen. Morgan Sullivan in the guide book makes the following key points linking these to the cross sectional diagram above:
  • The outcrops at Kilbaha Bay are characterized by compensationally stacked, very broad channelized sheets which represent the transition from channels to sheets.
  • These elements are up to a thousand meters (3270 feet) wide and B to 13 meters (26 to 42 feet) thick. Their bases tend to be non-erosional, suggesting that they are primarily aggradational in origin. In general, these channel complexes do not infill erosional scours; rather they are compensationally stacked due preexisting highs related to underlying channel complexes.
  • Individual elements can be further subdivided into distinct axis and margin facies associations. Highly amalgamated, massive sandstones characterize axial deposits. Away from the axis, beds become distinctly less amalgamated and extremely continuous to produce laterally extensive, layered wings at the margins.
  • Net-to-gross ratios for these channelized sheets range from 70 to 90% with an average of 80%.
  • Detailed bed-by-bed correlations show that these sandstones have lengths much greater than the dimensions of the Kilbaha Bay outcrop, while mudstones have much shorter lengths (Fig. 9). Therefore, the key to understanding reservoir continuity and internal heterogeneities that affect reservoir performance is knowing the thickness and lengths of mudstone barriers and not the distribution of sandstones.
  • 80% of these mudstones are less than 0.3 meters (1 foot) thick and have bed lengths less than 200 meters (655 feet).
  • Although this is a relatively high net-te-gross reservoir type with excellent lateral continuity, the vertical continuity would be moderate to low. This is due to the preserved interbedded mudstones, even though only 5 to 10% of these mudstones have lengths approaching or greater than 700 meters (2295 feet). It is these continuous mudstones that likely would produce significant vertical barriers to fluid flow.
Wednesday, September 25, 2013
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