Who would raise the cat's tail if not the cat himself. But in defense I can say that I can partially echo what others say, and many thanks to them.
"Murtoos are typically 30–200 m in length and 30–200 m in width with a relief of commonly <5 m. Murtoos have straight and steep edges, a triangular tip oriented parallel to ice-flow direction, and an asymmetric longitudinal profile with a shorter, but steeper down-ice slope." "Murtoos are composed primarily of loose diamicton with some sorted beds."
"The first modern mention of murtoos (though not yet named) appeared in an
article written by Seppälä. The author identified the triangular landforms
from LiDAR images, and referred to them as ”fan-like hollows of plucked
or glaciotectonic rafts” with a general edge height of 1-3 meters (Seppälä,
2016, p. 4), in contrast to later publications originating from both Finland
and Sweden, where murtoos are considered to be positive mounds."
Ok, that description concerned one place. But I also described it this way: "Tightly spaced fan-like fragment lines produce diamond patterned moraine surfaces." So as I have used the term glaciotectonic or deformational, in this context, it is much the same as "Murtoo-like" or "concerning Murtoos". In my classification (see below) Murtoos are partly covered by both category 3): fan-like and transverse edges of plucked depressions and category 5): deformational or glaciotectonic mound or ridge. All Murtoo fields do not show clear fan-like faults, but fault or edge system can be more complicated, skewed or obscure.
Erosion and deposition in this case are perhaps like the choice of whether the glass is half empty or full. For the time being, I prefer the negative option in most cases until proven otherwise. I think the simplest explanation for triangles and corresponding forms are the motion-conjugated symmetric oblique edges ( that were created by glaciotectonic fracturing of the substrate as the glacier moved forward. The meltwater weighted formation option does not explain triangles "at all".
So I have dealt as the first current (2015, 2016a,b) researcher triangular morainic landforms, Murtoos, but in a broader context and with a different genetic interpretation (deformation or glaciotectonics): the so-called subglacial glaciotectonic hypothesis (SGH). According to SGH, these would be mainly erosional forms, ie in the case of triangular ridges, they would be the result of the erosion of ridge spacings directly as a result of glacial/glaciotectonic activity. It may have preceded and followed also the subglacial meltwater processes, but in essence, it would have been, in my early interpretation, subglacial block-erosion.
Glaciotectonic activity may have been not only plucking but also ductile deformation, less deforming or reforming, and even possible squeezing or massflow. These are alternative glaciotectonics related processes for the subglacial meltwater erosion and deposition. Thus, I have formed a short description of the classification of the related mostly subglacial glaciotectonic or deformational formations: Five types of mostly erosional glaciotectonic landforms were recognized: (1) plucked lee side, (2) hill-hole pair, (3) fan-like and transverse edges of plucked depressions, (4) sporadic plucked hollows, and (5) deformational or glaciotectonic mound or ridge. The Murtoo topography is essentially same as the class 3: fan-like and transverse edges of plucked depressions or diamond-shaped morainic topography or fan-like hollows; and as the class 5): deformational or glaciotectonic mound or ridge.
As simple speculation, possible meltwater related processes behind these landforms could be subglacial sheet-like outbursts, which could explain wide erosional spacings between hummocks and also sorted layers of hummocks, but not so obviously diagonal edges or triangles. The source of meltwater flows could also be moulins, which could explain often punctuate proximal endings of the erosional fans. But moulins are maybe not so good explanation for close adjacent shapes? These meltwaters could occasionally freeze onto the substrate and glacier and thus cause glaciotectonics. If the moulins reached a depth of up to one hundred meters, it positioned the origin fairly close to the front of the glacier. The differentiation of glacial landscapes from low valleys with rough (plucking?) moraine topography and smooth drumlinized (abrasion) higher areas could also be related to transverse drainage of meltwater on, in or under the glacier? But the overall rough image of these landscapes speaks for glaciotectonics and secondly for all kinds of erosion. Fragmentary and triangular shapes are most easily interpreted as directly attributable to the characteristics and motion of the glacier, even if, for example, there are also partial meltwater flows at the beginning and end of the overall process. The moving ice could produce pairs of symmetrical displacements to the substrate with an angular opening in the direction of motion, which explains the fracture lines that produce the triangles. Apparently, both the glacier directly and perhaps in some cases, meltwater then caused erosion in the areas between the positive shapes, and with the possible glacial deposition inside the triangle, a typical morphology formed. Also, it is good to remember that especially along existing watercourses some fragmented looking topography can partly or wholly be the result of quite late postglacial fluvial erosion.
