Lmst

Algorithm Raises New Questions About Cascadia Earthquake Record
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https://phys.org/news/2024-08-algorithm-cascadia-earthquake.html <-- shared technical article
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https://doi.org/10.1130/B37343.1 <-- shared paper
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#GIS #spatial #mapping #sedimentology #geology #structuralgeology #platetectonics #CascadiaSubductionZone #PNW #PacificNorthwest #spatialanalysis #spatiotemporal #forests #tsunamis #earthquake #risk #hazard #timing #naturaldisasters #geomorphology #geomorphometry #turbidite #corrleation #causation #model #modeling #massmovement #landslides #algorithm #machinelearning #AI

section and maps - Expanded view of cores from Cascadia, Pacific Northwest, USA

maps - Figure 1. (A) Map of central–northern Cascadia, which lies offshore Oregon (OR) and Washington (WA), USA. (B) Inset of cores from the Juan de Fuca and Willapa channels, tributaries of the Cascadia Channel, at the base of the lower continental slope. (C) Inset of cores from the Cascadia Channel on the abyssal plain. (D) Inset of Hydrate Ridge Basin. (E) Inset of core locations from Rogue Apron.

geologic cross section / schematic - Cascadia subduction zone

A small #outcrop of the #Squantum Member of the #Roxbury #Conglomerate

These #rocks are in the #BostonBay Group, which is currently dated to #Neoproterozoic. The Squantum Member was interpreted as a #tillite, possibly associated with the #Gaskiers #glaciation, although there a scant signs like scratched pebbles or faceted cobbles. It is currently commonly interpreted as a #debrite (debris flow). Details in captions.
#geology #glacier #turbidite #Quincy #Boston #Massachusetts #NewEngland

Google Eart view of Squantum, Quincy, immediately southeast of Boston, Massachusetts USA. The small outcrop examined here is near the red pin. The “classic” Squantum cliff and beach exposures are near the pin for Myles Standish Cairn.

My photo of a pice of float, not attached to bedrock. I interpret depositional up is at the bottom of this photo, and it is reverse graded as a debris pulse flowed over fine-grained sediments deposited in quieter conditions. Cell phone for scale.

My photo of a piece of float, probably Squantum Member. There is compressive metamorphic foliation expressed as squashed clasts; compression is perpendicular to the pencil.

Abrupt change in grain size in Squantum Member, depositional up is interpreted to be top right.

Anomalous pebble in layered #sedimentary #rock

An angular pebble is conformably surrounded by argillaceous and sandy layers in this #photograph of the #Neoproterozoic #Squantum Member of the #Roxbury Conglomerate. The wide range of clast sizes led to an interpretation as a #glacial #tillite thru the 1970s, but the Squantum Member is now mostly interpreted as a #debrisFlow (#debrite or #turbidite). My #photo.

#Boston #fieldTrip #UMassBoston

In this color photo, a greenish circa 2 centimeter pebble at the center is bounded by distorted quasi parallel bedding below and above. Image height is about 10 cm. White balance card at right has an inch scale visible. My photo.

Deformed bedding in meta#sedimentary #rocks

The horizontal bedding of the #Squantum Member of the #Roxbury Conglomerate (#Neoproterozoic, #Boston Bay Group) has been disturbed locally.

In the #glacial #tillite interpretation of the Squantum (favored through at least the 1970s), the distortion might be caused by glaciotectonic drag at the ice base. The current interpretation as a #debrite or #turbidite would probably attribute the deformations to synsedimentary slumping. My #photo. #fieldTrip

This color photo show a circa 12 cm vertical extent of sedimentary rocks. In the upper part of the image, beds are inclined upward to the left. Near the center of the image, a bed has been rolled over itself. These features could have been caused by sediment slumping leftward, possibly in a debris flow. There is a white balance card with inch and centimeter scales at the bottom left. My photo.

The #glacier went that-a-way

The #striations on this face of the #Ediacaran (ca. 560 Ma) #Squantum Member of the #Roxbury #Conglomerate were probably left by the #Pleistocene #Laurentide ice sheet, which retreated ca. 12 ka. The striations have the right orientation, from northwest to southeast.

The Squantum Member was once interpreted as a (#glacial) #tillite. The most common contemporary model is a peri-#Gondwana #debrite (#turbidite).

My #photo. #Boston #geology #NewEngland #fieldTrip

Shallow scratches extend roughly left to right across this image, which is about 20 cm tall. The compass at the left center of the image indicates the scratches are on a NW-SE axis, consistent with the movement of the Pleistocene ice sheet in this region. The cracks are from extensive deformation. There are scales on the sides of the compass. My photo.

Turbidites above the Resurrection Peninsula Ophiolite, Alaska.

We now know that the turbidites on Fox Island, near Seward AK are part of the Paleocene Orca Group.

Spectacular in scale, and thickness.

#Alaska #Ophiolite #Turbidite #Paleocene #Chugach

Cliff of layers of turbidites along a marine coastline with a small red zodiac in the foreground.

Interbedded tuffaceous and fine grained siliciclastic layers in the Cambridge Argillite, a Neoproterozoic member of the Boston Bay Group, above the Roxbury Conglomerate. Usually interpreted as a turbidite distal to the Roxbury.

#turbidite #geology #turbidites #rocks

#Turbidite

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