Aquetong Creek-Lahaska Creek Drainage Divide area, Solebury Township, Bucks County

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Northeast oriented Aquetong Creek headwaters originate north and east of Lahaska, Pa area and eventually reach the south oriented Delaware River while south and south-southwest oriented Lahaska Creek flows just west and south of Lahaska to reach Mill Creek and then Neshaminy Creek, which eventually flows to a southwest oriented Delaware River segment. Through valleys link the two opposing streams and can be seen in figure 1 below where location 1 identifies headwaters of a northeast Aquetong Creek tributary and location 2 identifies the elbow of capture where Lahaska Creek turns to flow in a south-southwest direction. Aquetong Creek water flows in a northeast direction from location 1 to location 3 and then turns to flow in a south-southeast direction to location 6 before turning again to flow in a northeast and east-northeast direction to reach the Delaware River at location 7. Headwaters of other Aquetong Creek tributaries can be found at locations 4, 5, and 9. Location 8 identifies headwaters of a southeast, southwest, and south oriented tributary to northeast, southeast, and northeast oriented Pidcock Creek, which eventually reaches the south oriented Delaware River near the figure 1 south edge.

 

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Figure 1; Aquetong Creek-Lahaska Creek drainage divide area, See text for details, United States Geological Survey map digitally presented using National Geographic TOPO software. 

Many landforms seen in figure 1 are oriented in a southwest-to-northeast direction, although Solebury Mountain is a significant exception. Solebury Mountain is shown on the Pennsylvania Geological Survey web applications map as being composed of diabase and was formed when molten igneous rock intruded into the surrounding bedrock. The southwest-to-northeast orientation of the other surrounding landforms is related to the orientation of geologic features within that surrounding bedrock and deep erosion has shaped the regional landscape in accordance with those geologic features. Ridges are composed of erosion resistant bedrock while less erosion resistant materials underlie the elongate valleys. While the region has probably experienced a long and complicated geologic history the concern here is with the erosion event that shaped the landforms.

The present day landscape was shaped during an erosion event that began with a regional surface at least as high or higher than the highest points seen in figure 1. At that time the Delaware River valley did not exist and there was no Delaware River, nor did any of the present day Delaware River tributaries or tributary valleys exist. Instead massive and prolonged southwest oriented floods were moving across the entire region. The flood flow direction was probably shaped as floodwaters eroded shallow channels into the underlying bedrock in which southwest-to-northeast oriented structures are common throughout southeast Pennsylvania. Floodwaters were flowing in complexes of shallow anastomosing channels (diverging and converging channels) with water also moving freely between the channels. The deep Delaware River valley eroded headward into this high-level surface to capture the southwest oriented flood flow.

Before eroding the south oriented valley seen in figure 1 the deep Delaware River valley eroded headward (from present day Philadelphia) almost to present day Trenton, NJ along what must have been a major southwest oriented flood flow channel. South of Trenton the actively eroding and deep Delaware River valley ceased to erode headward along that southwest oriented flood flow channel and began to erode headward in a north direction across the southwest oriented flood flow. In each case immense volumes of water were required to erode the deep Delaware River valley headward and comparable volumes of water were required to erode major Delaware River tributary valleys.

The deep east, southeast, and south oriented Neshaminy Creek valley (not seen in figure 1 and located west of the figure 1) eroded headward from the actively eroding southwest oriented Delaware River valley segment at a time when the deep south-oriented Delaware River valley seen in figure 1 had yet to be eroded. Headward erosion of the deep Neshaminy Creek valley and its south oriented tributary valleys captured southwest oriented flood flow moving across the figure 1 map region. These captured floodwaters then began to erode deep southwest-oriented valleys headward into the figure 1 map region and south oriented valleys eroded headward from these deep southwest oriented valleys to capture more of the flood flow. For example the south oriented Pidcock Creek tributary originating at location 8 is located in one such south oriented valley and the south oriented Lahaska Creek valley north of location 2 is another such south oriented valley. It is possible the south oriented valley between locations 3 and 6 and the southeast oriented valleys seen at locations 4 and 5 were also initiated at this time.

Before the deep Neshaminy Creek valley could become the dominant regional drainage route the deep south-oriented Delaware River valley eroded headward across the southwest oriented flood flow channels that were supplying floodwaters to the actively eroding Neshaminy Creek drainage basin. Headward erosion of the deep Delaware River valley beheaded the southwest oriented flood flow channels in sequence from south to north. Floodwaters on northeast ends of the beheaded flood flow channels reversed direction to flow in a northeast direction to the newly eroded and much deeper Delaware River valley. Because the flood flow channels diverged and converged and because floodwaters were moving freely between the flood flow channels reversed flow on newly beheaded flood flow channels captured floodwaters from yet to be beheaded flood flow channels. Such captures enabled the development of significant northeast oriented drainage basins such as the Aquetong Creek drainage basin seen in figure 1.

The Aquetong Creek elbow of capture at location 3 and the through valley between locations 1 and 2 were created when a northeast oriented reversed flood flow channel between locations 6 and 7 successfully captured and reversed flood flow on a yet to be beheaded flood flow channel at location 3. The through valley between locations 9 and 8 was created when reversed flow on that same northeast oriented flood flow channel beheaded and reversed a southwest oriented flood flow channel at location 6, which in turn beheaded and reversed a southwest oriented flood flow channel at location 9. Southeast oriented valleys at locations 4 and 5 were eroded as reversed flow in the newly developed Aquetong Creek drainage basin captured southwest oriented flood flow moving across the northwest corner of figure 1. Erosion of the Aquetong Creek drainage basin ended when Delaware River valley headward erosion captured all southwest flood flow across the figure 1 northwest corner.

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